pwm: Changes for v6.19-rc1

Additional to the usual mix of core cleanups, driver changes, minor
 fixes and device tree updates the highlight this cycle is Rust support
 for the core and a first Rust driver both provided by Michal Wilczynski.
 Michal wrote about these changes on
 https://mwilczynski.dev/posts/bringing-rust-to-the-pwm-subsystem/ which
 is a nice read.
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Merge tag 'pwm/for-6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/ukleinek/linux

Pull pwm updates from Uwe Kleine-König:
 "In addition to the usual mix of core cleanups, driver changes, minor
  fixes and device tree updates the highlight this cycle is Rust support
  for the core and a first Rust driver both provided by Michal
  Wilczynski.

  Michal wrote about these changes on

    https://mwilczynski.dev/posts/bringing-rust-to-the-pwm-subsystem/

  which is a nice read"

* tag 'pwm/for-6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/ukleinek/linux: (22 commits)
  pwm: rzg2l-gpt: Allow checking period_tick cache value only if sibling channel is enabled
  pwm: bcm2835: Make sure the channel is enabled after pwm_request()
  pwm: mediatek: Make use of struct_size macro
  pwm: mediatek: Remove unneeded semicolon
  pwm: airoha: Add support for EN7581 SoC
  pwm: mediatek: Convert to waveform API
  pwm: max7360: Clean MAX7360 code
  pwm: Drop unused function pwm_apply_args()
  pwm: Use %u to printf unsigned int pwm_chip::npwm and pwm_chip::id
  pwm: Simplify printf to emit chip->npwm in $debugfs/pwm
  pwm: th1520: Use module_pwm_platform_driver! macro
  pwm: th1520: Fix clippy warning for redundant struct field init
  pwm: Fix Rust formatting
  dt-bindings: pwm: thead: Add T-HEAD TH1520 PWM controller
  pwm: Add Rust driver for T-HEAD TH1520 SoC
  rust: pwm: Fix broken intra-doc link
  rust: pwm: Drop wrapping of PWM polarity and state
  rust: pwm: Add module_pwm_platform_driver! macro
  rust: pwm: Add complete abstraction layer
  rust: pwm: Add Kconfig and basic data structures
  ...

Documentation/devicetree/bindings/pwm/thead,th1520-pwm.yaml

@@ -0,0 +1,48 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/thead,th1520-pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: T-HEAD TH1520 PWM controller
+
+maintainers:
+  - Michal Wilczynski <m.wilczynski@samsung.com>
+
+allOf:
+  - $ref: pwm.yaml#
+
+properties:
+  compatible:
+    const: thead,th1520-pwm
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: SoC PWM clock
+
+  "#pwm-cells":
+    const: 3
+
+required:
+  - compatible
+  - reg
+  - clocks
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/thead,th1520-clk-ap.h>
+    soc {
+      #address-cells = <2>;
+      #size-cells = <2>;
+      pwm@ffec01c000 {
+          compatible = "thead,th1520-pwm";
+          reg = <0xff 0xec01c000 0x0 0x4000>;
+          clocks = <&clk CLK_PWM>;
+          #pwm-cells = <3>;
+      };
+    };

MAINTAINERS

@@ -20871,6 +20871,14 @@ F:	include/linux/pwm.h
 F:	include/linux/pwm_backlight.h
 K:	pwm_(config|apply_might_sleep|apply_atomic|ops)
 
+PWM SUBSYSTEM BINDINGS [RUST]
+M:	Michal Wilczynski <m.wilczynski@samsung.com>
+L:	linux-pwm@vger.kernel.org
+L:	rust-for-linux@vger.kernel.org
+S:	Maintained
+F:	rust/helpers/pwm.c
+F:	rust/kernel/pwm.rs
+
 PXA GPIO DRIVER
 M:	Robert Jarzmik <robert.jarzmik@free.fr>
 L:	linux-gpio@vger.kernel.org
@@ -22293,6 +22301,7 @@ F:	Documentation/devicetree/bindings/firmware/thead,th1520-aon.yaml
 F:	Documentation/devicetree/bindings/mailbox/thead,th1520-mbox.yaml
 F:	Documentation/devicetree/bindings/net/thead,th1520-gmac.yaml
 F:	Documentation/devicetree/bindings/pinctrl/thead,th1520-pinctrl.yaml
+F:	Documentation/devicetree/bindings/pwm/thead,th1520-pwm.yaml
 F:	Documentation/devicetree/bindings/reset/thead,th1520-reset.yaml
 F:	arch/riscv/boot/dts/thead/
 F:	drivers/clk/thead/clk-th1520-ap.c
@@ -22303,6 +22312,7 @@ F:	drivers/pinctrl/pinctrl-th1520.c
 F:	drivers/pmdomain/thead/
 F:	drivers/power/reset/th1520-aon-reboot.c
 F:	drivers/power/sequencing/pwrseq-thead-gpu.c
+F:	drivers/pwm/pwm_th1520.rs
 F:	drivers/reset/reset-th1520.c
 F:	include/dt-bindings/clock/thead,th1520-clk-ap.h
 F:	include/dt-bindings/power/thead,th1520-power.h

drivers/pwm/Kconfig

@@ -63,6 +63,16 @@ config PWM_ADP5585
 	  This option enables support for the PWM function found in the Analog
 	  Devices ADP5585.
 
+config PWM_AIROHA
+	tristate "Airoha PWM support"
+	depends on ARCH_AIROHA || COMPILE_TEST
+	select REGMAP_MMIO
+	help
+	  Generic PWM framework driver for Airoha SoC.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-airoha.
+
 config PWM_APPLE
 	tristate "Apple SoC PWM support"
 	depends on ARCH_APPLE || COMPILE_TEST
@@ -748,6 +758,17 @@ config PWM_TEGRA
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-tegra.
 
+config PWM_TH1520
+	tristate "TH1520 PWM support"
+	depends on RUST
+	select RUST_PWM_ABSTRACTIONS
+	help
+	  This option enables the driver for the PWM controller found on the
+	  T-HEAD TH1520 SoC.
+
+	  To compile this driver as a module, choose M here; the module
+	  will be called pwm-th1520. If you are unsure, say N.
+
 config PWM_TIECAP
 	tristate "ECAP PWM support"
 	depends on ARCH_OMAP2PLUS || ARCH_DAVINCI_DA8XX || ARCH_KEYSTONE || ARCH_K3 || COMPILE_TEST
@@ -819,4 +840,16 @@ config PWM_XILINX
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-xilinx.
 
+ config RUST_PWM_ABSTRACTIONS
+	bool
+	depends on RUST
+	help
+	  This option enables the safe Rust abstraction layer for the PWM
+	  subsystem. It provides idiomatic wrappers and traits necessary for
+	  writing PWM controller drivers in Rust.
+
+	  The abstractions handle resource management (like memory and reference
+	  counting) and provide safe interfaces to the underlying C core,
+	  allowing driver logic to be written in safe Rust.
+
 endif

drivers/pwm/Makefile

@@ -2,6 +2,7 @@
 obj-$(CONFIG_PWM)		+= core.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
 obj-$(CONFIG_PWM_ADP5585)	+= pwm-adp5585.o
+obj-$(CONFIG_PWM_AIROHA)	+= pwm-airoha.o
 obj-$(CONFIG_PWM_APPLE)		+= pwm-apple.o
 obj-$(CONFIG_PWM_ARGON_FAN_HAT)	+= pwm-argon-fan-hat.o
 obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
@@ -68,6 +69,7 @@ obj-$(CONFIG_PWM_STMPE)		+= pwm-stmpe.o
 obj-$(CONFIG_PWM_SUN4I)		+= pwm-sun4i.o
 obj-$(CONFIG_PWM_SUNPLUS)	+= pwm-sunplus.o
 obj-$(CONFIG_PWM_TEGRA)		+= pwm-tegra.o
+obj-$(CONFIG_PWM_TH1520)	+= pwm_th1520.o
 obj-$(CONFIG_PWM_TIECAP)	+= pwm-tiecap.o
 obj-$(CONFIG_PWM_TIEHRPWM)	+= pwm-tiehrpwm.o
 obj-$(CONFIG_PWM_TWL)		+= pwm-twl.o

drivers/pwm/core.c

@@ -1608,12 +1608,13 @@ void pwmchip_put(struct pwm_chip *chip)
 }
 EXPORT_SYMBOL_GPL(pwmchip_put);
 
-static void pwmchip_release(struct device *pwmchip_dev)
+void pwmchip_release(struct device *pwmchip_dev)
 {
 	struct pwm_chip *chip = pwmchip_from_dev(pwmchip_dev);
 
 	kfree(chip);
 }
+EXPORT_SYMBOL_GPL(pwmchip_release);
 
 struct pwm_chip *pwmchip_alloc(struct device *parent, unsigned int npwm, size_t sizeof_priv)
 {
@@ -2696,11 +2697,10 @@ static int pwm_seq_show(struct seq_file *s, void *v)
 {
 	struct pwm_chip *chip = v;
 
-	seq_printf(s, "%s%d: %s/%s, %d PWM device%s\n",
+	seq_printf(s, "%s%u: %s/%s, npwm: %u\n",
 		   (char *)s->private, chip->id,
 		   pwmchip_parent(chip)->bus ? pwmchip_parent(chip)->bus->name : "no-bus",
-		   dev_name(pwmchip_parent(chip)), chip->npwm,
+		   dev_name(pwmchip_parent(chip)), chip->npwm);
-		   (chip->npwm != 1) ? "s" : "");
 
 	pwm_dbg_show(chip, s);
 

drivers/pwm/pwm-airoha.c

@@ -0,0 +1,622 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2022 Markus Gothe <markus.gothe@genexis.eu>
+ * Copyright 2025 Christian Marangi <ansuelsmth@gmail.com>
+ *
+ *  Limitations:
+ *  - Only 8 concurrent waveform generators are available for 8 combinations of
+ *    duty_cycle and period. Waveform generators are shared between 16 GPIO
+ *    pins and 17 SIPO GPIO pins.
+ *  - Supports only normal polarity.
+ *  - On configuration the currently running period is completed.
+ *  - Minimum supported period is 4 ms
+ *  - Maximum supported period is 1s
+ */
+
+#include <linux/array_size.h>
+#include <linux/bitfield.h>
+#include <linux/bitmap.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/math64.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+#define AIROHA_PWM_REG_SGPIO_LED_DATA		0x0024
+#define AIROHA_PWM_SGPIO_LED_DATA_SHIFT_FLAG	BIT(31)
+#define AIROHA_PWM_SGPIO_LED_DATA_DATA		GENMASK(16, 0)
+
+#define AIROHA_PWM_REG_SGPIO_CLK_DIVR		0x0028
+#define AIROHA_PWM_SGPIO_CLK_DIVR		GENMASK(1, 0)
+#define AIROHA_PWM_SGPIO_CLK_DIVR_32		FIELD_PREP_CONST(AIROHA_PWM_SGPIO_CLK_DIVR, 3)
+#define AIROHA_PWM_SGPIO_CLK_DIVR_16		FIELD_PREP_CONST(AIROHA_PWM_SGPIO_CLK_DIVR, 2)
+#define AIROHA_PWM_SGPIO_CLK_DIVR_8		FIELD_PREP_CONST(AIROHA_PWM_SGPIO_CLK_DIVR, 1)
+#define AIROHA_PWM_SGPIO_CLK_DIVR_4		FIELD_PREP_CONST(AIROHA_PWM_SGPIO_CLK_DIVR, 0)
+
+#define AIROHA_PWM_REG_SGPIO_CLK_DLY		0x002c
+
+#define AIROHA_PWM_REG_SIPO_FLASH_MODE_CFG	0x0030
+#define AIROHA_PWM_SERIAL_GPIO_FLASH_MODE	BIT(1)
+#define AIROHA_PWM_SERIAL_GPIO_MODE_74HC164	BIT(0)
+
+#define AIROHA_PWM_REG_GPIO_FLASH_PRD_SET(_n)	(0x003c + (4 * (_n)))
+#define AIROHA_PWM_REG_GPIO_FLASH_PRD_SHIFT(_n) (16 * (_n))
+#define AIROHA_PWM_GPIO_FLASH_PRD_LOW		GENMASK(15, 8)
+#define AIROHA_PWM_GPIO_FLASH_PRD_HIGH		GENMASK(7, 0)
+
+#define AIROHA_PWM_REG_GPIO_FLASH_MAP(_n)	(0x004c + (4 * (_n)))
+#define AIROHA_PWM_REG_GPIO_FLASH_MAP_SHIFT(_n) (4 * (_n))
+#define AIROHA_PWM_GPIO_FLASH_EN		BIT(3)
+#define AIROHA_PWM_GPIO_FLASH_SET_ID		GENMASK(2, 0)
+
+/* Register map is equal to GPIO flash map */
+#define AIROHA_PWM_REG_SIPO_FLASH_MAP(_n)	(0x0054 + (4 * (_n)))
+
+#define AIROHA_PWM_REG_CYCLE_CFG_VALUE(_n)	(0x0098 + (4 * (_n)))
+#define AIROHA_PWM_REG_CYCLE_CFG_SHIFT(_n)	(8 * (_n))
+#define AIROHA_PWM_WAVE_GEN_CYCLE		GENMASK(7, 0)
+
+/* GPIO/SIPO flash map handles 8 pins in one register */
+#define AIROHA_PWM_PINS_PER_FLASH_MAP		8
+/* Cycle(Period) registers handles 4 generators in one 32-bit register */
+#define AIROHA_PWM_BUCKET_PER_CYCLE_CFG		4
+/* Flash(Duty) producer handles 2 generators in one 32-bit register */
+#define AIROHA_PWM_BUCKET_PER_FLASH_PROD	2
+
+#define AIROHA_PWM_NUM_BUCKETS			8
+/*
+ * The first 16 GPIO pins, GPIO0-GPIO15, are mapped into 16 PWM channels, 0-15.
+ * The SIPO GPIO pins are 17 pins which are mapped into 17 PWM channels, 16-32.
+ * However, we've only got 8 concurrent waveform generators and can therefore
+ * only use up to 8 different combinations of duty cycle and period at a time.
+ */
+#define AIROHA_PWM_NUM_GPIO			16
+#define AIROHA_PWM_NUM_SIPO			17
+#define AIROHA_PWM_MAX_CHANNELS			(AIROHA_PWM_NUM_GPIO + AIROHA_PWM_NUM_SIPO)
+
+struct airoha_pwm_bucket {
+	/* Concurrent access protected by PWM core */
+	int used;
+	u32 period_ticks;
+	u32 duty_ticks;
+};
+
+struct airoha_pwm {
+	struct regmap *regmap;
+
+	DECLARE_BITMAP(initialized, AIROHA_PWM_MAX_CHANNELS);
+
+	struct airoha_pwm_bucket buckets[AIROHA_PWM_NUM_BUCKETS];
+
+	/* Cache bucket used by each pwm channel */
+	u8 channel_bucket[AIROHA_PWM_MAX_CHANNELS];
+};
+
+/* The PWM hardware supports periods between 4 ms and 1 s */
+#define AIROHA_PWM_PERIOD_TICK_NS	(4 * NSEC_PER_MSEC)
+#define AIROHA_PWM_PERIOD_MAX_NS	(1 * NSEC_PER_SEC)
+/* It is represented internally as 1/250 s between 1 and 250. Unit is ticks. */
+#define AIROHA_PWM_PERIOD_MIN		1
+#define AIROHA_PWM_PERIOD_MAX		250
+/* Duty cycle is relative with 255 corresponding to 100% */
+#define AIROHA_PWM_DUTY_FULL		255
+
+static void airoha_pwm_get_flash_map_addr_and_shift(unsigned int hwpwm,
+						    u32 *addr, u32 *shift)
+{
+	unsigned int offset, hwpwm_bit;
+
+	if (hwpwm >= AIROHA_PWM_NUM_GPIO) {
+		unsigned int sipohwpwm = hwpwm - AIROHA_PWM_NUM_GPIO;
+
+		offset = sipohwpwm / AIROHA_PWM_PINS_PER_FLASH_MAP;
+		hwpwm_bit = sipohwpwm % AIROHA_PWM_PINS_PER_FLASH_MAP;
+
+		/* One FLASH_MAP register handles 8 pins */
+		*shift = AIROHA_PWM_REG_GPIO_FLASH_MAP_SHIFT(hwpwm_bit);
+		*addr = AIROHA_PWM_REG_SIPO_FLASH_MAP(offset);
+	} else {
+		offset = hwpwm / AIROHA_PWM_PINS_PER_FLASH_MAP;
+		hwpwm_bit = hwpwm % AIROHA_PWM_PINS_PER_FLASH_MAP;
+
+		/* One FLASH_MAP register handles 8 pins */
+		*shift = AIROHA_PWM_REG_GPIO_FLASH_MAP_SHIFT(hwpwm_bit);
+		*addr = AIROHA_PWM_REG_GPIO_FLASH_MAP(offset);
+	}
+}
+
+static u32 airoha_pwm_get_period_ticks_from_ns(u32 period_ns)
+{
+	return period_ns / AIROHA_PWM_PERIOD_TICK_NS;
+}
+
+static u32 airoha_pwm_get_duty_ticks_from_ns(u32 period_ns, u32 duty_ns)
+{
+	return mul_u64_u32_div(duty_ns, AIROHA_PWM_DUTY_FULL, period_ns);
+}
+
+static u32 airoha_pwm_get_period_ns_from_ticks(u32 period_tick)
+{
+	return period_tick * AIROHA_PWM_PERIOD_TICK_NS;
+}
+
+static u32 airoha_pwm_get_duty_ns_from_ticks(u32 period_tick, u32 duty_tick)
+{
+	u32 period_ns = period_tick * AIROHA_PWM_PERIOD_TICK_NS;
+
+	/*
+	 * Overflow can't occur in multiplication as duty_tick is just 8 bit
+	 * and period_ns is clamped to AIROHA_PWM_PERIOD_MAX_NS and fit in a
+	 * u64.
+	 */
+	return DIV_U64_ROUND_UP(duty_tick * period_ns, AIROHA_PWM_DUTY_FULL);
+}
+
+static int airoha_pwm_get_bucket(struct airoha_pwm *pc, int bucket,
+				 u64 *period_ns, u64 *duty_ns)
+{
+	struct regmap *map = pc->regmap;
+	u32 period_tick, duty_tick;
+	unsigned int offset;
+	u32 shift, val;
+	int ret;
+
+	offset = bucket / AIROHA_PWM_BUCKET_PER_CYCLE_CFG;
+	shift = bucket % AIROHA_PWM_BUCKET_PER_CYCLE_CFG;
+	shift = AIROHA_PWM_REG_CYCLE_CFG_SHIFT(shift);
+
+	ret = regmap_read(map, AIROHA_PWM_REG_CYCLE_CFG_VALUE(offset), &val);
+	if (ret)
+		return ret;
+
+	period_tick = FIELD_GET(AIROHA_PWM_WAVE_GEN_CYCLE, val >> shift);
+	*period_ns = airoha_pwm_get_period_ns_from_ticks(period_tick);
+
+	offset = bucket / AIROHA_PWM_BUCKET_PER_FLASH_PROD;
+	shift = bucket % AIROHA_PWM_BUCKET_PER_FLASH_PROD;
+	shift = AIROHA_PWM_REG_GPIO_FLASH_PRD_SHIFT(shift);
+
+	ret = regmap_read(map, AIROHA_PWM_REG_GPIO_FLASH_PRD_SET(offset),
+			  &val);
+	if (ret)
+		return ret;
+
+	duty_tick = FIELD_GET(AIROHA_PWM_GPIO_FLASH_PRD_HIGH, val >> shift);
+	*duty_ns = airoha_pwm_get_duty_ns_from_ticks(period_tick, duty_tick);
+
+	return 0;
+}
+
+static int airoha_pwm_get_generator(struct airoha_pwm *pc, u32 duty_ticks,
+				    u32 period_ticks)
+{
+	int best = -ENOENT, unused = -ENOENT;
+	u32 duty_ns, best_duty_ns = 0;
+	u32 best_period_ticks = 0;
+	unsigned int i;
+
+	duty_ns = airoha_pwm_get_duty_ns_from_ticks(period_ticks, duty_ticks);
+
+	for (i = 0; i < ARRAY_SIZE(pc->buckets); i++) {
+		struct airoha_pwm_bucket *bucket = &pc->buckets[i];
+		u32 bucket_period_ticks = bucket->period_ticks;
+		u32 bucket_duty_ticks = bucket->duty_ticks;
+
+		/* If found, save an unused bucket to return it later */
+		if (!bucket->used) {
+			unused = i;
+			continue;
+		}
+
+		/* We found a matching bucket, exit early */
+		if (duty_ticks == bucket_duty_ticks &&
+		    period_ticks == bucket_period_ticks)
+			return i;
+
+		/*
+		 * Unlike duty cycle zero, which can be handled by
+		 * disabling PWM, a generator is needed for full duty
+		 * cycle but it can be reused regardless of period
+		 */
+		if (duty_ticks == AIROHA_PWM_DUTY_FULL &&
+		    bucket_duty_ticks == AIROHA_PWM_DUTY_FULL)
+			return i;
+
+		/*
+		 * With an unused bucket available, skip searching for
+		 * a bucket to recycle (closer to the requested period/duty)
+		 */
+		if (unused >= 0)
+			continue;
+
+		/* Ignore bucket with invalid period */
+		if (bucket_period_ticks > period_ticks)
+			continue;
+
+		/*
+		 * Search for a bucket closer to the requested period
+		 * that has the maximal possible period that isn't bigger
+		 * than the requested period. For that period pick the maximal
+		 * duty cycle that isn't bigger than the requested duty_cycle.
+		 */
+		if (bucket_period_ticks >= best_period_ticks) {
+			u32 bucket_duty_ns = airoha_pwm_get_duty_ns_from_ticks(bucket_period_ticks,
+									       bucket_duty_ticks);
+
+			/* Skip bucket that goes over the requested duty */
+			if (bucket_duty_ns > duty_ns)
+				continue;
+
+			if (bucket_duty_ns > best_duty_ns) {
+				best_period_ticks = bucket_period_ticks;
+				best_duty_ns = bucket_duty_ns;
+				best = i;
+			}
+		}
+	}
+
+	/* Return an unused bucket or the best one found (if ever) */
+	return unused >= 0 ? unused : best;
+}
+
+static void airoha_pwm_release_bucket_config(struct airoha_pwm *pc,
+					     unsigned int hwpwm)
+{
+	int bucket;
+
+	/* Nothing to clear, PWM channel never used */
+	if (!test_bit(hwpwm, pc->initialized))
+		return;
+
+	bucket = pc->channel_bucket[hwpwm];
+	pc->buckets[bucket].used--;
+}
+
+static int airoha_pwm_apply_bucket_config(struct airoha_pwm *pc, unsigned int bucket,
+					  u32 duty_ticks, u32 period_ticks)
+{
+	u32 mask, shift, val;
+	u32 offset;
+	int ret;
+
+	offset = bucket / AIROHA_PWM_BUCKET_PER_CYCLE_CFG;
+	shift = bucket % AIROHA_PWM_BUCKET_PER_CYCLE_CFG;
+	shift = AIROHA_PWM_REG_CYCLE_CFG_SHIFT(shift);
+
+	/* Configure frequency divisor */
+	mask = AIROHA_PWM_WAVE_GEN_CYCLE << shift;
+	val = FIELD_PREP(AIROHA_PWM_WAVE_GEN_CYCLE, period_ticks) << shift;
+	ret = regmap_update_bits(pc->regmap, AIROHA_PWM_REG_CYCLE_CFG_VALUE(offset),
+				 mask, val);
+	if (ret)
+		return ret;
+
+	offset = bucket / AIROHA_PWM_BUCKET_PER_FLASH_PROD;
+	shift = bucket % AIROHA_PWM_BUCKET_PER_FLASH_PROD;
+	shift = AIROHA_PWM_REG_GPIO_FLASH_PRD_SHIFT(shift);
+
+	/* Configure duty cycle */
+	mask = AIROHA_PWM_GPIO_FLASH_PRD_HIGH << shift;
+	val = FIELD_PREP(AIROHA_PWM_GPIO_FLASH_PRD_HIGH, duty_ticks) << shift;
+	ret = regmap_update_bits(pc->regmap, AIROHA_PWM_REG_GPIO_FLASH_PRD_SET(offset),
+				 mask, val);
+	if (ret)
+		return ret;
+
+	mask = AIROHA_PWM_GPIO_FLASH_PRD_LOW << shift;
+	val = FIELD_PREP(AIROHA_PWM_GPIO_FLASH_PRD_LOW,
+			 AIROHA_PWM_DUTY_FULL - duty_ticks) << shift;
+	return regmap_update_bits(pc->regmap, AIROHA_PWM_REG_GPIO_FLASH_PRD_SET(offset),
+				  mask, val);
+}
+
+static int airoha_pwm_consume_generator(struct airoha_pwm *pc,
+					u32 duty_ticks, u32 period_ticks,
+					unsigned int hwpwm)
+{
+	bool config_bucket = false;
+	int bucket, ret;
+
+	/*
+	 * Search for a bucket that already satisfies duty and period
+	 * or an unused one.
+	 * If not found, -ENOENT is returned.
+	 */
+	bucket = airoha_pwm_get_generator(pc, duty_ticks, period_ticks);
+	if (bucket < 0)
+		return bucket;
+
+	/* Release previous used bucket (if any) */
+	airoha_pwm_release_bucket_config(pc, hwpwm);
+
+	if (!pc->buckets[bucket].used)
+		config_bucket = true;
+	pc->buckets[bucket].used++;
+
+	if (config_bucket) {
+		pc->buckets[bucket].period_ticks = period_ticks;
+		pc->buckets[bucket].duty_ticks = duty_ticks;
+		ret = airoha_pwm_apply_bucket_config(pc, bucket,
+						     duty_ticks,
+						     period_ticks);
+		if (ret) {
+			pc->buckets[bucket].used--;
+			return ret;
+		}
+	}
+
+	return bucket;
+}
+
+static int airoha_pwm_sipo_init(struct airoha_pwm *pc)
+{
+	u32 val;
+	int ret;
+
+	ret = regmap_clear_bits(pc->regmap, AIROHA_PWM_REG_SIPO_FLASH_MODE_CFG,
+				AIROHA_PWM_SERIAL_GPIO_MODE_74HC164);
+	if (ret)
+		return ret;
+
+	/* Configure shift register chip clock timings, use 32x divisor */
+	ret = regmap_write(pc->regmap, AIROHA_PWM_REG_SGPIO_CLK_DIVR,
+			   AIROHA_PWM_SGPIO_CLK_DIVR_32);
+	if (ret)
+		return ret;
+
+	/*
+	 * Configure the shift register chip clock delay. This needs
+	 * to be configured based on the chip characteristics when the SoC
+	 * apply the shift register configuration.
+	 * This doesn't affect actual PWM operation and is only specific to
+	 * the shift register chip.
+	 *
+	 * For 74HC164 we set it to 0.
+	 *
+	 * For reference, the actual delay applied is the internal clock
+	 * feed to the SGPIO chip + 1.
+	 *
+	 * From documentation is specified that clock delay should not be
+	 * greater than (AIROHA_PWM_REG_SGPIO_CLK_DIVR / 2) - 1.
+	 */
+	ret = regmap_write(pc->regmap, AIROHA_PWM_REG_SGPIO_CLK_DLY, 0);
+	if (ret)
+		return ret;
+
+	/*
+	 * It is necessary to explicitly shift out all zeros after muxing
+	 * to initialize the shift register before enabling PWM
+	 * mode because in PWM mode SIPO will not start shifting until
+	 * it needs to output a non-zero value (bit 31 of led_data
+	 * indicates shifting in progress and it must return to zero
+	 * before led_data can be written or PWM mode can be set).
+	 */
+	ret = regmap_read_poll_timeout(pc->regmap, AIROHA_PWM_REG_SGPIO_LED_DATA, val,
+				       !(val & AIROHA_PWM_SGPIO_LED_DATA_SHIFT_FLAG),
+				       10, 200 * USEC_PER_MSEC);
+	if (ret)
+		return ret;
+
+	ret = regmap_clear_bits(pc->regmap, AIROHA_PWM_REG_SGPIO_LED_DATA,
+				AIROHA_PWM_SGPIO_LED_DATA_DATA);
+	if (ret)
+		return ret;
+	ret = regmap_read_poll_timeout(pc->regmap, AIROHA_PWM_REG_SGPIO_LED_DATA, val,
+				       !(val & AIROHA_PWM_SGPIO_LED_DATA_SHIFT_FLAG),
+				       10, 200 * USEC_PER_MSEC);
+	if (ret)
+		return ret;
+
+	/* Set SIPO in PWM mode */
+	return regmap_set_bits(pc->regmap, AIROHA_PWM_REG_SIPO_FLASH_MODE_CFG,
+			       AIROHA_PWM_SERIAL_GPIO_FLASH_MODE);
+}
+
+static int airoha_pwm_config_flash_map(struct airoha_pwm *pc,
+				       unsigned int hwpwm, int index)
+{
+	unsigned int addr;
+	u32 shift;
+	int ret;
+
+	airoha_pwm_get_flash_map_addr_and_shift(hwpwm, &addr, &shift);
+
+	/* negative index means disable PWM channel */
+	if (index < 0) {
+		/*
+		 * If we need to disable the PWM, we just put low the
+		 * GPIO. No need to setup buckets.
+		 */
+		return regmap_clear_bits(pc->regmap, addr,
+					 AIROHA_PWM_GPIO_FLASH_EN << shift);
+	}
+
+	ret = regmap_update_bits(pc->regmap, addr,
+				 AIROHA_PWM_GPIO_FLASH_SET_ID << shift,
+				 FIELD_PREP(AIROHA_PWM_GPIO_FLASH_SET_ID, index) << shift);
+	if (ret)
+		return ret;
+
+	return regmap_set_bits(pc->regmap, addr, AIROHA_PWM_GPIO_FLASH_EN << shift);
+}
+
+static int airoha_pwm_config(struct airoha_pwm *pc, struct pwm_device *pwm,
+			     u32 period_ticks, u32 duty_ticks)
+{
+	unsigned int hwpwm = pwm->hwpwm;
+	int bucket, ret;
+
+	bucket = airoha_pwm_consume_generator(pc, duty_ticks, period_ticks,
+					      hwpwm);
+	if (bucket < 0)
+		return bucket;
+
+	ret = airoha_pwm_config_flash_map(pc, hwpwm, bucket);
+	if (ret) {
+		pc->buckets[bucket].used--;
+		return ret;
+	}
+
+	__set_bit(hwpwm, pc->initialized);
+	pc->channel_bucket[hwpwm] = bucket;
+
+	/*
+	 * SIPO are special GPIO attached to a shift register chip. The handling
+	 * of this chip is internal to the SoC that takes care of applying the
+	 * values based on the flash map. To apply a new flash map, it's needed
+	 * to trigger a refresh on the shift register chip.
+	 * If a SIPO is getting configuring , always reinit the shift register
+	 * chip to make sure the correct flash map is applied.
+	 * Skip reconfiguring the shift register if the related hwpwm
+	 * is disabled (as it doesn't need to be mapped).
+	 */
+	if (hwpwm >= AIROHA_PWM_NUM_GPIO) {
+		ret = airoha_pwm_sipo_init(pc);
+		if (ret) {
+			airoha_pwm_release_bucket_config(pc, hwpwm);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+static void airoha_pwm_disable(struct airoha_pwm *pc, struct pwm_device *pwm)
+{
+	/* Disable PWM and release the bucket */
+	airoha_pwm_config_flash_map(pc, pwm->hwpwm, -1);
+	airoha_pwm_release_bucket_config(pc, pwm->hwpwm);
+
+	__clear_bit(pwm->hwpwm, pc->initialized);
+
+	/* If no SIPO is used, disable the shift register chip */
+	if (!bitmap_read(pc->initialized,
+			 AIROHA_PWM_NUM_GPIO, AIROHA_PWM_NUM_SIPO))
+		regmap_clear_bits(pc->regmap, AIROHA_PWM_REG_SIPO_FLASH_MODE_CFG,
+				  AIROHA_PWM_SERIAL_GPIO_FLASH_MODE);
+}
+
+static int airoha_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			    const struct pwm_state *state)
+{
+	struct airoha_pwm *pc = pwmchip_get_drvdata(chip);
+	u32 period_ticks, duty_ticks;
+	u32 period_ns, duty_ns;
+
+	if (!state->enabled) {
+		airoha_pwm_disable(pc, pwm);
+		return 0;
+	}
+
+	/* Only normal polarity is supported */
+	if (state->polarity == PWM_POLARITY_INVERSED)
+		return -EINVAL;
+
+	/* Exit early if period is less than minimum supported */
+	if (state->period < AIROHA_PWM_PERIOD_TICK_NS)
+		return -EINVAL;
+
+	/* Clamp period to MAX supported value */
+	if (state->period > AIROHA_PWM_PERIOD_MAX_NS)
+		period_ns = AIROHA_PWM_PERIOD_MAX_NS;
+	else
+		period_ns = state->period;
+
+	/* Validate duty to configured period */
+	if (state->duty_cycle > period_ns)
+		duty_ns = period_ns;
+	else
+		duty_ns = state->duty_cycle;
+
+	/* Convert period ns to ticks */
+	period_ticks = airoha_pwm_get_period_ticks_from_ns(period_ns);
+	/* Convert period ticks to ns again for cosistent duty tick calculation */
+	period_ns = airoha_pwm_get_period_ns_from_ticks(period_ticks);
+	duty_ticks = airoha_pwm_get_duty_ticks_from_ns(period_ns, duty_ns);
+
+	return airoha_pwm_config(pc, pwm, period_ticks, duty_ticks);
+}
+
+static int airoha_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				struct pwm_state *state)
+{
+	struct airoha_pwm *pc = pwmchip_get_drvdata(chip);
+	int ret, hwpwm = pwm->hwpwm;
+	u32 addr, shift, val;
+	u8 bucket;
+
+	airoha_pwm_get_flash_map_addr_and_shift(hwpwm, &addr, &shift);
+
+	ret = regmap_read(pc->regmap, addr, &val);
+	if (ret)
+		return ret;
+
+	state->enabled = FIELD_GET(AIROHA_PWM_GPIO_FLASH_EN, val >> shift);
+	if (!state->enabled)
+		return 0;
+
+	state->polarity = PWM_POLARITY_NORMAL;
+
+	bucket = FIELD_GET(AIROHA_PWM_GPIO_FLASH_SET_ID, val >> shift);
+	return airoha_pwm_get_bucket(pc, bucket, &state->period,
+				     &state->duty_cycle);
+}
+
+static const struct pwm_ops airoha_pwm_ops = {
+	.apply = airoha_pwm_apply,
+	.get_state = airoha_pwm_get_state,
+};
+
+static int airoha_pwm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct airoha_pwm *pc;
+	struct pwm_chip *chip;
+	int ret;
+
+	chip = devm_pwmchip_alloc(dev, AIROHA_PWM_MAX_CHANNELS, sizeof(*pc));
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+
+	chip->ops = &airoha_pwm_ops;
+	pc = pwmchip_get_drvdata(chip);
+
+	pc->regmap = device_node_to_regmap(dev_of_node(dev->parent));
+	if (IS_ERR(pc->regmap))
+		return dev_err_probe(dev, PTR_ERR(pc->regmap), "Failed to get PWM regmap\n");
+
+	ret = devm_pwmchip_add(dev, chip);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to add PWM chip\n");
+
+	return 0;
+}
+
+static const struct of_device_id airoha_pwm_of_match[] = {
+	{ .compatible = "airoha,en7581-pwm" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, airoha_pwm_of_match);
+
+static struct platform_driver airoha_pwm_driver = {
+	.driver = {
+		.name = "pwm-airoha",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = airoha_pwm_of_match,
+	},
+	.probe = airoha_pwm_probe,
+};
+module_platform_driver(airoha_pwm_driver);
+
+MODULE_AUTHOR("Lorenzo Bianconi <lorenzo@kernel.org>");
+MODULE_AUTHOR("Markus Gothe <markus.gothe@genexis.eu>");
+MODULE_AUTHOR("Benjamin Larsson <benjamin.larsson@genexis.eu>");
+MODULE_AUTHOR("Christian Marangi <ansuelsmth@gmail.com>");
+MODULE_DESCRIPTION("Airoha EN7581 PWM driver");
+MODULE_LICENSE("GPL");

drivers/pwm/pwm-bcm2835.c

@@ -34,29 +34,6 @@ static inline struct bcm2835_pwm *to_bcm2835_pwm(struct pwm_chip *chip)
 	return pwmchip_get_drvdata(chip);
 }
 
-static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
-{
-	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
-	u32 value;
-
-	value = readl(pc->base + PWM_CONTROL);
-	value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
-	value |= (PWM_MODE << PWM_CONTROL_SHIFT(pwm->hwpwm));
-	writel(value, pc->base + PWM_CONTROL);
-
-	return 0;
-}
-
-static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
-{
-	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
-	u32 value;
-
-	value = readl(pc->base + PWM_CONTROL);
-	value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
-	writel(value, pc->base + PWM_CONTROL);
-}
-
 static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			     const struct pwm_state *state)
 {
@@ -102,6 +79,9 @@ static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	/* set polarity */
 	val = readl(pc->base + PWM_CONTROL);
 
+	val &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
+	val |= PWM_MODE << PWM_CONTROL_SHIFT(pwm->hwpwm);
+
 	if (state->polarity == PWM_POLARITY_NORMAL)
 		val &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
 	else
@@ -119,8 +99,6 @@ static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 }
 
 static const struct pwm_ops bcm2835_pwm_ops = {
-	.request = bcm2835_pwm_request,
-	.free = bcm2835_pwm_free,
 	.apply = bcm2835_pwm_apply,
 };
 

drivers/pwm/pwm-max7360.c

@@ -75,7 +75,7 @@ static int max7360_pwm_round_waveform_tohw(struct pwm_chip *chip,
 			duty_steps = MAX7360_PWM_MAX - 1;
 	}
 
-	wfhw->duty_steps = min(MAX7360_PWM_MAX, duty_steps);
+	wfhw->duty_steps = duty_steps;
 	wfhw->enabled = !!wf->period_length_ns;
 
 	if (wf->period_length_ns && wf->period_length_ns < MAX7360_PWM_PERIOD_NS)

drivers/pwm/pwm-mediatek.c

@@ -135,50 +135,51 @@ static inline u32 pwm_mediatek_readl(struct pwm_mediatek_chip *chip,
 		     num * chip->soc->chanreg_width + offset);
 }
 
-static void pwm_mediatek_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+struct pwm_mediatek_waveform {
-{
+	u32 enable;
-	struct pwm_mediatek_chip *pc = to_pwm_mediatek_chip(chip);
+	u32 con;
-	u32 value;
+	u32 width;
-
+	u32 thres;
-	value = readl(pc->regs);
+};
-	value |= BIT(pwm->hwpwm);
+
-	writel(value, pc->regs);
+static int pwm_mediatek_round_waveform_tohw(struct pwm_chip *chip, struct pwm_device *pwm,
-}
+					    const struct pwm_waveform *wf, void *_wfhw)
-
-static void pwm_mediatek_disable(struct pwm_chip *chip, struct pwm_device *pwm)
-{
-	struct pwm_mediatek_chip *pc = to_pwm_mediatek_chip(chip);
-	u32 value;
-
-	value = readl(pc->regs);
-	value &= ~BIT(pwm->hwpwm);
-	writel(value, pc->regs);
-}
-
-static int pwm_mediatek_config(struct pwm_chip *chip, struct pwm_device *pwm,
-			       u64 duty_ns, u64 period_ns)
 {
+	struct pwm_mediatek_waveform *wfhw = _wfhw;
 	struct pwm_mediatek_chip *pc = to_pwm_mediatek_chip(chip);
 	u32 clkdiv, enable;
-	u32 reg_width = PWMDWIDTH, reg_thres = PWMTHRES;
 	u64 cnt_period, cnt_duty;
 	unsigned long clk_rate;
-	int ret;
+	int ret = 0;
 
-	ret = pwm_mediatek_clk_enable(pc, pwm->hwpwm);
+	if (wf->period_length_ns == 0) {
-	if (ret < 0)
+		*wfhw = (typeof(*wfhw)){
-		return ret;
+			.enable = 0,
+		};
+
+		return 0;
+	}
+
+	if (!pc->clk_pwms[pwm->hwpwm].rate) {
+		struct clk *clk = pc->clk_pwms[pwm->hwpwm].clk;
+
+		ret = clk_prepare_enable(clk);
+		if (ret)
+			return ret;
+
+		pc->clk_pwms[pwm->hwpwm].rate = clk_get_rate(clk);
+
+		clk_disable_unprepare(clk);
+	}
 
 	clk_rate = pc->clk_pwms[pwm->hwpwm].rate;
+	if (clk_rate == 0 || clk_rate > 1000000000)
+		return -EINVAL;
 
-	/* Make sure we use the bus clock and not the 26MHz clock */
+	cnt_period = mul_u64_u64_div_u64(wf->period_length_ns, clk_rate, NSEC_PER_SEC);
-	if (pc->soc->pwm_ck_26m_sel_reg)
-		writel(0, pc->regs + pc->soc->pwm_ck_26m_sel_reg);
-
-	cnt_period = mul_u64_u64_div_u64(period_ns, clk_rate, NSEC_PER_SEC);
 	if (cnt_period == 0) {
-		ret = -ERANGE;
+		cnt_period = 1;
-		goto out;
+		ret = 1;
 	}
 
 	if (cnt_period > FIELD_MAX(PWMDWIDTH_PERIOD) + 1) {
@@ -193,7 +194,7 @@ static int pwm_mediatek_config(struct pwm_chip *chip, struct pwm_device *pwm,
 		clkdiv = 0;
 	}
 
-	cnt_duty = mul_u64_u64_div_u64(duty_ns, clk_rate, NSEC_PER_SEC) >> clkdiv;
+	cnt_duty = mul_u64_u64_div_u64(wf->duty_length_ns, clk_rate, NSEC_PER_SEC) >> clkdiv;
 	if (cnt_duty > cnt_period)
 		cnt_duty = cnt_period;
 
@@ -206,26 +207,173 @@ static int pwm_mediatek_config(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	cnt_period -= 1;
 
-	dev_dbg(&chip->dev, "pwm#%u: %lld/%lld @%lu -> CON: %x, PERIOD: %llx, DUTY: %llx\n",
+	dev_dbg(&chip->dev, "pwm#%u: %lld/%lld @%lu -> ENABLE: %x, CON: %x, PERIOD: %llx, DUTY: %llx\n",
-		pwm->hwpwm, duty_ns, period_ns, clk_rate, clkdiv, cnt_period, cnt_duty);
+		pwm->hwpwm, wf->duty_length_ns, wf->period_length_ns, clk_rate,
+		enable, clkdiv, cnt_period, cnt_duty);
+
+	*wfhw = (typeof(*wfhw)){
+		.enable = enable,
+		.con = clkdiv,
+		.width = cnt_period,
+		.thres = cnt_duty,
+	};
+
+	return ret;
+}
+
+static int pwm_mediatek_round_waveform_fromhw(struct pwm_chip *chip, struct pwm_device *pwm,
+					      const void *_wfhw, struct pwm_waveform *wf)
+{
+	const struct pwm_mediatek_waveform *wfhw = _wfhw;
+	struct pwm_mediatek_chip *pc = to_pwm_mediatek_chip(chip);
+	u32 clkdiv, cnt_period, cnt_duty;
+	unsigned long clk_rate;
+
+	/*
+	 * When _wfhw was populated, the clock was on, so .rate is
+	 * already set appropriately.
+	 */
+	clk_rate = pc->clk_pwms[pwm->hwpwm].rate;
+
+	if (wfhw->enable) {
+		clkdiv = FIELD_GET(PWMCON_CLKDIV, wfhw->con);
+		cnt_period = FIELD_GET(PWMDWIDTH_PERIOD, wfhw->width);
+		cnt_duty = FIELD_GET(PWMTHRES_DUTY, wfhw->thres);
 
-	if (pc->soc->pwm45_fixup && pwm->hwpwm > 2) {
 		/*
-		 * PWM[4,5] has distinct offset for PWMDWIDTH and PWMTHRES
+		 * cnt_period is a 13 bit value, NSEC_PER_SEC is 30 bits wide
-		 * from the other PWMs on MT7623.
+		 * and clkdiv is less than 8, so the multiplication doesn't
+		 * overflow an u64.
 		 */
-		reg_width = PWM45DWIDTH_FIXUP;
+		*wf = (typeof(*wf)){
-		reg_thres = PWM45THRES_FIXUP;
+			.period_length_ns =
+				DIV_ROUND_UP_ULL((u64)(cnt_period + 1) * NSEC_PER_SEC << clkdiv, clk_rate),
+			.duty_length_ns =
+				DIV_ROUND_UP_ULL((u64)(cnt_duty + 1) * NSEC_PER_SEC << clkdiv, clk_rate),
+		};
+	} else {
+		clkdiv = 0;
+		cnt_period = 0;
+		cnt_duty = 0;
+
+		/*
+		 * .enable = 0 is also used for too small duty_cycle values, so
+		 * report the HW as being enabled to communicate the minimal
+		 * period.
+		 */
+		*wf = (typeof(*wf)){
+			.period_length_ns =
+				DIV_ROUND_UP_ULL(NSEC_PER_SEC, clk_rate),
+			.duty_length_ns = 0,
+		};
 	}
 
-	pwm_mediatek_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | clkdiv);
+	dev_dbg(&chip->dev, "pwm#%u: ENABLE: %x, CLKDIV: %x, PERIOD: %x, DUTY: %x @%lu -> %lld/%lld\n",
-	pwm_mediatek_writel(pc, pwm->hwpwm, reg_width, cnt_period);
+		pwm->hwpwm, wfhw->enable, clkdiv, cnt_period, cnt_duty, clk_rate,
+		wf->duty_length_ns, wf->period_length_ns);
+
+	return 0;
+}
+
+static int pwm_mediatek_read_waveform(struct pwm_chip *chip,
+				      struct pwm_device *pwm, void *_wfhw)
+{
+	struct pwm_mediatek_waveform *wfhw = _wfhw;
+	struct pwm_mediatek_chip *pc = to_pwm_mediatek_chip(chip);
+	u32 enable, clkdiv, cnt_period, cnt_duty;
+	u32 reg_width = PWMDWIDTH, reg_thres = PWMTHRES;
+	int ret;
+
+	ret = pwm_mediatek_clk_enable(pc, pwm->hwpwm);
+	if (ret < 0)
+		return ret;
+
+	enable = readl(pc->regs) & BIT(pwm->hwpwm);
 
 	if (enable) {
-		pwm_mediatek_writel(pc, pwm->hwpwm, reg_thres, cnt_duty);
+		if (pc->soc->pwm45_fixup && pwm->hwpwm > 2) {
-		pwm_mediatek_enable(chip, pwm);
+			/*
+			 * PWM[4,5] has distinct offset for PWMDWIDTH and PWMTHRES
+			 * from the other PWMs on MT7623.
+			 */
+			reg_width = PWM45DWIDTH_FIXUP;
+			reg_thres = PWM45THRES_FIXUP;
+		}
+
+		clkdiv = FIELD_GET(PWMCON_CLKDIV, pwm_mediatek_readl(pc, pwm->hwpwm, PWMCON));
+		cnt_period = FIELD_GET(PWMDWIDTH_PERIOD, pwm_mediatek_readl(pc, pwm->hwpwm, reg_width));
+		cnt_duty = FIELD_GET(PWMTHRES_DUTY, pwm_mediatek_readl(pc, pwm->hwpwm, reg_thres));
+
+		*wfhw = (typeof(*wfhw)){
+			.enable = enable,
+			.con = BIT(15) | clkdiv,
+			.width = cnt_period,
+			.thres = cnt_duty,
+		};
 	} else {
-		pwm_mediatek_disable(chip, pwm);
+		*wfhw = (typeof(*wfhw)){
+			.enable = 0,
+		};
+	}
+
+	pwm_mediatek_clk_disable(pc, pwm->hwpwm);
+
+	return ret;
+}
+
+static int pwm_mediatek_write_waveform(struct pwm_chip *chip,
+				       struct pwm_device *pwm, const void *_wfhw)
+{
+	const struct pwm_mediatek_waveform *wfhw = _wfhw;
+	struct pwm_mediatek_chip *pc = to_pwm_mediatek_chip(chip);
+	u32 ctrl;
+	int ret;
+
+	ret = pwm_mediatek_clk_enable(pc, pwm->hwpwm);
+	if (ret < 0)
+		return ret;
+
+	ctrl = readl(pc->regs);
+
+	if (wfhw->enable) {
+		u32 reg_width = PWMDWIDTH, reg_thres = PWMTHRES;
+
+		if (pc->soc->pwm45_fixup && pwm->hwpwm > 2) {
+			/*
+			 * PWM[4,5] has distinct offset for PWMDWIDTH and PWMTHRES
+			 * from the other PWMs on MT7623.
+			 */
+			reg_width = PWM45DWIDTH_FIXUP;
+			reg_thres = PWM45THRES_FIXUP;
+		}
+
+		if (!(ctrl & BIT(pwm->hwpwm))) {
+			/*
+			 * The clks are already on, just increasing the usage
+			 * counter doesn't fail.
+			 */
+			ret = pwm_mediatek_clk_enable(pc, pwm->hwpwm);
+			if (unlikely(ret < 0))
+				goto out;
+
+			ctrl |= BIT(pwm->hwpwm);
+			writel(ctrl, pc->regs);
+		}
+
+		/* Make sure we use the bus clock and not the 26MHz clock */
+		if (pc->soc->pwm_ck_26m_sel_reg)
+			writel(0, pc->regs + pc->soc->pwm_ck_26m_sel_reg);
+
+		pwm_mediatek_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | wfhw->con);
+		pwm_mediatek_writel(pc, pwm->hwpwm, reg_width, wfhw->width);
+		pwm_mediatek_writel(pc, pwm->hwpwm, reg_thres, wfhw->thres);
+	} else {
+		if (ctrl & BIT(pwm->hwpwm)) {
+			ctrl &= ~BIT(pwm->hwpwm);
+			writel(ctrl, pc->regs);
+
+			pwm_mediatek_clk_disable(pc, pwm->hwpwm);
+		}
 	}
 
 out:
@@ -234,93 +382,12 @@ static int pwm_mediatek_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	return ret;
 }
 
-static int pwm_mediatek_apply(struct pwm_chip *chip, struct pwm_device *pwm,
-			      const struct pwm_state *state)
-{
-	struct pwm_mediatek_chip *pc = to_pwm_mediatek_chip(chip);
-	int err;
-
-	if (state->polarity != PWM_POLARITY_NORMAL)
-		return -EINVAL;
-
-	if (!state->enabled) {
-		if (pwm->state.enabled) {
-			pwm_mediatek_disable(chip, pwm);
-			pwm_mediatek_clk_disable(pc, pwm->hwpwm);
-		}
-
-		return 0;
-	}
-
-	err = pwm_mediatek_config(chip, pwm, state->duty_cycle, state->period);
-	if (err)
-		return err;
-
-	if (!pwm->state.enabled)
-		err = pwm_mediatek_clk_enable(pc, pwm->hwpwm);
-
-	return err;
-}
-
-static int pwm_mediatek_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
-				  struct pwm_state *state)
-{
-	struct pwm_mediatek_chip *pc = to_pwm_mediatek_chip(chip);
-	int ret;
-	u32 enable;
-	u32 reg_width = PWMDWIDTH, reg_thres = PWMTHRES;
-
-	if (pc->soc->pwm45_fixup && pwm->hwpwm > 2) {
-		/*
-		 * PWM[4,5] has distinct offset for PWMDWIDTH and PWMTHRES
-		 * from the other PWMs on MT7623.
-		 */
-		reg_width = PWM45DWIDTH_FIXUP;
-		reg_thres = PWM45THRES_FIXUP;
-	}
-
-	ret = pwm_mediatek_clk_enable(pc, pwm->hwpwm);
-	if (ret < 0)
-		return ret;
-
-	enable = readl(pc->regs);
-	if (enable & BIT(pwm->hwpwm)) {
-		u32 clkdiv, cnt_period, cnt_duty;
-		unsigned long clk_rate;
-
-		clk_rate = pc->clk_pwms[pwm->hwpwm].rate;
-
-		state->enabled = true;
-		state->polarity = PWM_POLARITY_NORMAL;
-
-		clkdiv = FIELD_GET(PWMCON_CLKDIV,
-				   pwm_mediatek_readl(pc, pwm->hwpwm, PWMCON));
-		cnt_period = FIELD_GET(PWMDWIDTH_PERIOD,
-				       pwm_mediatek_readl(pc, pwm->hwpwm, reg_width));
-		cnt_duty = FIELD_GET(PWMTHRES_DUTY,
-				     pwm_mediatek_readl(pc, pwm->hwpwm, reg_thres));
-
-		/*
-		 * cnt_period is a 13 bit value, NSEC_PER_SEC is 30 bits wide
-		 * and clkdiv is less than 8, so the multiplication doesn't
-		 * overflow an u64.
-		 */
-		state->period =
-			DIV_ROUND_UP_ULL((u64)cnt_period * NSEC_PER_SEC << clkdiv, clk_rate);
-		state->duty_cycle =
-			DIV_ROUND_UP_ULL((u64)cnt_duty * NSEC_PER_SEC << clkdiv, clk_rate);
-	} else {
-		state->enabled = false;
-	}
-
-	pwm_mediatek_clk_disable(pc, pwm->hwpwm);
-
-	return ret;
-}
-
 static const struct pwm_ops pwm_mediatek_ops = {
-	.apply = pwm_mediatek_apply,
+	.sizeof_wfhw = sizeof(struct pwm_mediatek_waveform),
-	.get_state = pwm_mediatek_get_state,
+	.round_waveform_tohw = pwm_mediatek_round_waveform_tohw,
+	.round_waveform_fromhw = pwm_mediatek_round_waveform_fromhw,
+	.read_waveform = pwm_mediatek_read_waveform,
+	.write_waveform = pwm_mediatek_write_waveform,
 };
 
 static int pwm_mediatek_init_used_clks(struct pwm_mediatek_chip *pc)
@@ -377,7 +444,7 @@ static int pwm_mediatek_probe(struct platform_device *pdev)
 	soc = of_device_get_match_data(&pdev->dev);
 
 	chip = devm_pwmchip_alloc(&pdev->dev, soc->num_pwms,
-				  sizeof(*pc) + soc->num_pwms * sizeof(*pc->clk_pwms));
+				  struct_size(pc, clk_pwms, soc->num_pwms));
 	if (IS_ERR(chip))
 		return PTR_ERR(chip);
 	pc = to_pwm_mediatek_chip(chip);

drivers/pwm/pwm-rzg2l-gpt.c

@@ -96,6 +96,11 @@ static inline unsigned int rzg2l_gpt_subchannel(unsigned int hwpwm)
 	return hwpwm & 0x1;
 }
 
+static inline unsigned int rzg2l_gpt_sibling(unsigned int hwpwm)
+{
+	return hwpwm ^ 0x1;
+}
+
 static void rzg2l_gpt_write(struct rzg2l_gpt_chip *rzg2l_gpt, u32 reg, u32 data)
 {
 	writel(data, rzg2l_gpt->mmio + reg);
@@ -271,10 +276,14 @@ static int rzg2l_gpt_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	 * in use with different settings.
 	 */
 	if (rzg2l_gpt->channel_request_count[ch] > 1) {
-		if (period_ticks < rzg2l_gpt->period_ticks[ch])
+		u8 sibling_ch = rzg2l_gpt_sibling(pwm->hwpwm);
-			return -EBUSY;
+
-		else
+		if (rzg2l_gpt_is_ch_enabled(rzg2l_gpt, sibling_ch)) {
+			if (period_ticks < rzg2l_gpt->period_ticks[ch])
+				return -EBUSY;
+
 			period_ticks = rzg2l_gpt->period_ticks[ch];
+		}
 	}
 
 	prescale = rzg2l_gpt_calculate_prescale(rzg2l_gpt, period_ticks);

drivers/pwm/pwm_th1520.rs

@@ -0,0 +1,387 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2025 Samsung Electronics Co., Ltd.
+// Author: Michal Wilczynski <m.wilczynski@samsung.com>
+
+//! Rust T-HEAD TH1520 PWM driver
+//!
+//! Limitations:
+//! - The period and duty cycle are controlled by 32-bit hardware registers,
+//!   limiting the maximum resolution.
+//! - The driver supports continuous output mode only; one-shot mode is not
+//!   implemented.
+//! - The controller hardware provides up to 6 PWM channels.
+//! - Reconfiguration is glitch free - new period and duty cycle values are
+//!   latched and take effect at the start of the next period.
+//! - Polarity is handled via a simple hardware inversion bit; arbitrary
+//!   duty cycle offsets are not supported.
+//! - Disabling a channel is achieved by configuring its duty cycle to zero to
+//!   produce a static low output. Clearing the `start` does not reliably
+//!   force the static inactive level defined by the `INACTOUT` bit. Hence
+//!   this method is not used in this driver.
+//!
+
+use core::ops::Deref;
+use kernel::{
+    c_str,
+    clk::Clk,
+    device::{Bound, Core, Device},
+    devres,
+    io::mem::IoMem,
+    of, platform,
+    prelude::*,
+    pwm, time,
+};
+
+const TH1520_MAX_PWM_NUM: u32 = 6;
+
+// Register offsets
+const fn th1520_pwm_chn_base(n: u32) -> usize {
+    (n * 0x20) as usize
+}
+
+const fn th1520_pwm_ctrl(n: u32) -> usize {
+    th1520_pwm_chn_base(n)
+}
+
+const fn th1520_pwm_per(n: u32) -> usize {
+    th1520_pwm_chn_base(n) + 0x08
+}
+
+const fn th1520_pwm_fp(n: u32) -> usize {
+    th1520_pwm_chn_base(n) + 0x0c
+}
+
+// Control register bits
+const TH1520_PWM_START: u32 = 1 << 0;
+const TH1520_PWM_CFG_UPDATE: u32 = 1 << 2;
+const TH1520_PWM_CONTINUOUS_MODE: u32 = 1 << 5;
+const TH1520_PWM_FPOUT: u32 = 1 << 8;
+
+const TH1520_PWM_REG_SIZE: usize = 0xB0;
+
+fn ns_to_cycles(ns: u64, rate_hz: u64) -> u64 {
+    const NSEC_PER_SEC_U64: u64 = time::NSEC_PER_SEC as u64;
+
+    (match ns.checked_mul(rate_hz) {
+        Some(product) => product,
+        None => u64::MAX,
+    }) / NSEC_PER_SEC_U64
+}
+
+fn cycles_to_ns(cycles: u64, rate_hz: u64) -> u64 {
+    const NSEC_PER_SEC_U64: u64 = time::NSEC_PER_SEC as u64;
+
+    // TODO: Replace with a kernel helper like `mul_u64_u64_div_u64_roundup`
+    // once available in Rust.
+    let numerator = cycles
+        .saturating_mul(NSEC_PER_SEC_U64)
+        .saturating_add(rate_hz - 1);
+
+    numerator / rate_hz
+}
+
+/// Hardware-specific waveform representation for TH1520.
+#[derive(Copy, Clone, Debug, Default)]
+struct Th1520WfHw {
+    period_cycles: u32,
+    duty_cycles: u32,
+    ctrl_val: u32,
+    enabled: bool,
+}
+
+/// The driver's private data struct. It holds all necessary devres managed resources.
+#[pin_data(PinnedDrop)]
+struct Th1520PwmDriverData {
+    #[pin]
+    iomem: devres::Devres<IoMem<TH1520_PWM_REG_SIZE>>,
+    clk: Clk,
+}
+
+// This `unsafe` implementation is a temporary necessity because the underlying `kernel::clk::Clk`
+// type does not yet expose `Send` and `Sync` implementations. This block should be removed
+// as soon as the clock abstraction provides these guarantees directly.
+// TODO: Remove those unsafe impl's when Clk will support them itself.
+
+// SAFETY: The `devres` framework requires the driver's private data to be `Send` and `Sync`.
+// We can guarantee this because the PWM core synchronizes all callbacks, preventing concurrent
+// access to the contained `iomem` and `clk` resources.
+unsafe impl Send for Th1520PwmDriverData {}
+
+// SAFETY: The same reasoning applies as for `Send`. The PWM core's synchronization
+// guarantees that it is safe for multiple threads to have shared access (`&self`)
+// to the driver data during callbacks.
+unsafe impl Sync for Th1520PwmDriverData {}
+
+impl pwm::PwmOps for Th1520PwmDriverData {
+    type WfHw = Th1520WfHw;
+
+    fn round_waveform_tohw(
+        chip: &pwm::Chip<Self>,
+        _pwm: &pwm::Device,
+        wf: &pwm::Waveform,
+    ) -> Result<pwm::RoundedWaveform<Self::WfHw>> {
+        let data = chip.drvdata();
+        let mut status = 0;
+
+        if wf.period_length_ns == 0 {
+            dev_dbg!(chip.device(), "Requested period is 0, disabling PWM.\n");
+
+            return Ok(pwm::RoundedWaveform {
+                status: 0,
+                hardware_waveform: Th1520WfHw {
+                    enabled: false,
+                    ..Default::default()
+                },
+            });
+        }
+
+        let rate_hz = data.clk.rate().as_hz() as u64;
+
+        let mut period_cycles = ns_to_cycles(wf.period_length_ns, rate_hz).min(u64::from(u32::MAX));
+
+        if period_cycles == 0 {
+            dev_dbg!(
+                chip.device(),
+                "Requested period {} ns is too small for clock rate {} Hz, rounding up.\n",
+                wf.period_length_ns,
+                rate_hz
+            );
+
+            period_cycles = 1;
+            status = 1;
+        }
+
+        let mut duty_cycles = ns_to_cycles(wf.duty_length_ns, rate_hz).min(u64::from(u32::MAX));
+
+        let mut ctrl_val = TH1520_PWM_CONTINUOUS_MODE;
+
+        let is_inversed = wf.duty_length_ns > 0
+            && wf.duty_offset_ns > 0
+            && wf.duty_offset_ns >= wf.period_length_ns.saturating_sub(wf.duty_length_ns);
+        if is_inversed {
+            duty_cycles = period_cycles - duty_cycles;
+        } else {
+            ctrl_val |= TH1520_PWM_FPOUT;
+        }
+
+        let wfhw = Th1520WfHw {
+            // The cast is safe because the value was clamped with `.min(u64::from(u32::MAX))`.
+            period_cycles: period_cycles as u32,
+            duty_cycles: duty_cycles as u32,
+            ctrl_val,
+            enabled: true,
+        };
+
+        dev_dbg!(
+            chip.device(),
+            "Requested: {}/{} ns [+{} ns] -> HW: {}/{} cycles, ctrl 0x{:x}, rate {} Hz\n",
+            wf.duty_length_ns,
+            wf.period_length_ns,
+            wf.duty_offset_ns,
+            wfhw.duty_cycles,
+            wfhw.period_cycles,
+            wfhw.ctrl_val,
+            rate_hz
+        );
+
+        Ok(pwm::RoundedWaveform {
+            status,
+            hardware_waveform: wfhw,
+        })
+    }
+
+    fn round_waveform_fromhw(
+        chip: &pwm::Chip<Self>,
+        _pwm: &pwm::Device,
+        wfhw: &Self::WfHw,
+        wf: &mut pwm::Waveform,
+    ) -> Result {
+        let data = chip.drvdata();
+        let rate_hz = data.clk.rate().as_hz() as u64;
+
+        if wfhw.period_cycles == 0 {
+            dev_dbg!(
+                chip.device(),
+                "HW state has zero period, reporting as disabled.\n"
+            );
+            *wf = pwm::Waveform::default();
+            return Ok(());
+        }
+
+        wf.period_length_ns = cycles_to_ns(u64::from(wfhw.period_cycles), rate_hz);
+
+        let duty_cycles = u64::from(wfhw.duty_cycles);
+
+        if (wfhw.ctrl_val & TH1520_PWM_FPOUT) != 0 {
+            wf.duty_length_ns = cycles_to_ns(duty_cycles, rate_hz);
+            wf.duty_offset_ns = 0;
+        } else {
+            let period_cycles = u64::from(wfhw.period_cycles);
+            let original_duty_cycles = period_cycles.saturating_sub(duty_cycles);
+
+            // For an inverted signal, `duty_length_ns` is the high time (period - low_time).
+            wf.duty_length_ns = cycles_to_ns(original_duty_cycles, rate_hz);
+            // The offset is the initial low time, which is what the hardware register provides.
+            wf.duty_offset_ns = cycles_to_ns(duty_cycles, rate_hz);
+        }
+
+        Ok(())
+    }
+
+    fn read_waveform(
+        chip: &pwm::Chip<Self>,
+        pwm: &pwm::Device,
+        parent_dev: &Device<Bound>,
+    ) -> Result<Self::WfHw> {
+        let data = chip.drvdata();
+        let hwpwm = pwm.hwpwm();
+        let iomem_accessor = data.iomem.access(parent_dev)?;
+        let iomap = iomem_accessor.deref();
+
+        let ctrl = iomap.try_read32(th1520_pwm_ctrl(hwpwm))?;
+        let period_cycles = iomap.try_read32(th1520_pwm_per(hwpwm))?;
+        let duty_cycles = iomap.try_read32(th1520_pwm_fp(hwpwm))?;
+
+        let wfhw = Th1520WfHw {
+            period_cycles,
+            duty_cycles,
+            ctrl_val: ctrl,
+            enabled: duty_cycles != 0,
+        };
+
+        dev_dbg!(
+            chip.device(),
+            "PWM-{}: read_waveform: Read hw state - period: {}, duty: {}, ctrl: 0x{:x}, enabled: {}",
+            hwpwm,
+            wfhw.period_cycles,
+            wfhw.duty_cycles,
+            wfhw.ctrl_val,
+            wfhw.enabled
+        );
+
+        Ok(wfhw)
+    }
+
+    fn write_waveform(
+        chip: &pwm::Chip<Self>,
+        pwm: &pwm::Device,
+        wfhw: &Self::WfHw,
+        parent_dev: &Device<Bound>,
+    ) -> Result {
+        let data = chip.drvdata();
+        let hwpwm = pwm.hwpwm();
+        let iomem_accessor = data.iomem.access(parent_dev)?;
+        let iomap = iomem_accessor.deref();
+        let duty_cycles = iomap.try_read32(th1520_pwm_fp(hwpwm))?;
+        let was_enabled = duty_cycles != 0;
+
+        if !wfhw.enabled {
+            dev_dbg!(chip.device(), "PWM-{}: Disabling channel.\n", hwpwm);
+            if was_enabled {
+                iomap.try_write32(wfhw.ctrl_val, th1520_pwm_ctrl(hwpwm))?;
+                iomap.try_write32(0, th1520_pwm_fp(hwpwm))?;
+                iomap.try_write32(
+                    wfhw.ctrl_val | TH1520_PWM_CFG_UPDATE,
+                    th1520_pwm_ctrl(hwpwm),
+                )?;
+            }
+            return Ok(());
+        }
+
+        iomap.try_write32(wfhw.ctrl_val, th1520_pwm_ctrl(hwpwm))?;
+        iomap.try_write32(wfhw.period_cycles, th1520_pwm_per(hwpwm))?;
+        iomap.try_write32(wfhw.duty_cycles, th1520_pwm_fp(hwpwm))?;
+        iomap.try_write32(
+            wfhw.ctrl_val | TH1520_PWM_CFG_UPDATE,
+            th1520_pwm_ctrl(hwpwm),
+        )?;
+
+        // The `TH1520_PWM_START` bit must be written in a separate, final transaction, and
+        // only when enabling the channel from a disabled state.
+        if !was_enabled {
+            iomap.try_write32(wfhw.ctrl_val | TH1520_PWM_START, th1520_pwm_ctrl(hwpwm))?;
+        }
+
+        dev_dbg!(
+            chip.device(),
+            "PWM-{}: Wrote {}/{} cycles",
+            hwpwm,
+            wfhw.duty_cycles,
+            wfhw.period_cycles,
+        );
+
+        Ok(())
+    }
+}
+
+#[pinned_drop]
+impl PinnedDrop for Th1520PwmDriverData {
+    fn drop(self: Pin<&mut Self>) {
+        self.clk.disable_unprepare();
+    }
+}
+
+struct Th1520PwmPlatformDriver;
+
+kernel::of_device_table!(
+    OF_TABLE,
+    MODULE_OF_TABLE,
+    <Th1520PwmPlatformDriver as platform::Driver>::IdInfo,
+    [(of::DeviceId::new(c_str!("thead,th1520-pwm")), ())]
+);
+
+impl platform::Driver for Th1520PwmPlatformDriver {
+    type IdInfo = ();
+    const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+
+    fn probe(
+        pdev: &platform::Device<Core>,
+        _id_info: Option<&Self::IdInfo>,
+    ) -> Result<Pin<KBox<Self>>> {
+        let dev = pdev.as_ref();
+        let request = pdev.io_request_by_index(0).ok_or(ENODEV)?;
+
+        let clk = Clk::get(dev, None)?;
+
+        clk.prepare_enable()?;
+
+        // TODO: Get exclusive ownership of the clock to prevent rate changes.
+        // The Rust equivalent of `clk_rate_exclusive_get()` is not yet available.
+        // This should be updated once it is implemented.
+        let rate_hz = clk.rate().as_hz();
+        if rate_hz == 0 {
+            dev_err!(dev, "Clock rate is zero\n");
+            return Err(EINVAL);
+        }
+
+        if rate_hz > time::NSEC_PER_SEC as usize {
+            dev_err!(
+                dev,
+                "Clock rate {} Hz is too high, not supported.\n",
+                rate_hz
+            );
+            return Err(EINVAL);
+        }
+
+        let chip = pwm::Chip::new(
+            dev,
+            TH1520_MAX_PWM_NUM,
+            try_pin_init!(Th1520PwmDriverData {
+                iomem <- request.iomap_sized::<TH1520_PWM_REG_SIZE>(),
+                clk <- clk,
+            }),
+        )?;
+
+        pwm::Registration::register(dev, chip)?;
+
+        Ok(KBox::new(Th1520PwmPlatformDriver, GFP_KERNEL)?.into())
+    }
+}
+
+kernel::module_pwm_platform_driver! {
+    type: Th1520PwmPlatformDriver,
+    name: "pwm-th1520",
+    authors: ["Michal Wilczynski <m.wilczynski@samsung.com>"],
+    description: "T-HEAD TH1520 PWM driver",
+    license: "GPL v2",
+}

include/linux/pwm.h

@@ -488,6 +488,12 @@ int __pwmchip_add(struct pwm_chip *chip, struct module *owner);
 #define pwmchip_add(chip) __pwmchip_add(chip, THIS_MODULE)
 void pwmchip_remove(struct pwm_chip *chip);
 
+/*
+ * For FFI wrapper use only:
+ * The Rust PWM abstraction needs this to properly free the pwm_chip.
+ */
+void pwmchip_release(struct device *dev);
+
 int __devm_pwmchip_add(struct device *dev, struct pwm_chip *chip, struct module *owner);
 #define devm_pwmchip_add(dev, chip) __devm_pwmchip_add(dev, chip, THIS_MODULE)
 
@@ -611,39 +617,6 @@ devm_fwnode_pwm_get(struct device *dev, struct fwnode_handle *fwnode,
 }
 #endif
 
-static inline void pwm_apply_args(struct pwm_device *pwm)
-{
-	struct pwm_state state = { };
-
-	/*
-	 * PWM users calling pwm_apply_args() expect to have a fresh config
-	 * where the polarity and period are set according to pwm_args info.
-	 * The problem is, polarity can only be changed when the PWM is
-	 * disabled.
-	 *
-	 * PWM drivers supporting hardware readout may declare the PWM device
-	 * as enabled, and prevent polarity setting, which changes from the
-	 * existing behavior, where all PWM devices are declared as disabled
-	 * at startup (even if they are actually enabled), thus authorizing
-	 * polarity setting.
-	 *
-	 * To fulfill this requirement, we apply a new state which disables
-	 * the PWM device and set the reference period and polarity config.
-	 *
-	 * Note that PWM users requiring a smooth handover between the
-	 * bootloader and the kernel (like critical regulators controlled by
-	 * PWM devices) will have to switch to the atomic API and avoid calling
-	 * pwm_apply_args().
-	 */
-
-	state.enabled = false;
-	state.polarity = pwm->args.polarity;
-	state.period = pwm->args.period;
-	state.usage_power = false;
-
-	pwm_apply_might_sleep(pwm, &state);
-}
-
 struct pwm_lookup {
 	struct list_head list;
 	const char *provider;

rust/bindings/bindings_helper.h

@@ -72,6 +72,7 @@
 #include <linux/pm_opp.h>
 #include <linux/poll.h>
 #include <linux/property.h>
+#include <linux/pwm.h>
 #include <linux/random.h>
 #include <linux/refcount.h>
 #include <linux/regulator/consumer.h>

rust/helpers/helpers.c

@@ -43,6 +43,7 @@
 #include "poll.c"
 #include "processor.c"
 #include "property.c"
+#include "pwm.c"
 #include "rbtree.c"
 #include "rcu.c"
 #include "refcount.c"

rust/helpers/pwm.c

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2025 Samsung Electronics Co., Ltd.
+// Author: Michal Wilczynski <m.wilczynski@samsung.com>
+
+#include <linux/pwm.h>
+
+struct device *rust_helper_pwmchip_parent(const struct pwm_chip *chip)
+{
+	return pwmchip_parent(chip);
+}
+
+void *rust_helper_pwmchip_get_drvdata(struct pwm_chip *chip)
+{
+	return pwmchip_get_drvdata(chip);
+}
+
+void rust_helper_pwmchip_set_drvdata(struct pwm_chip *chip, void *data)
+{
+	pwmchip_set_drvdata(chip, data);
+}

rust/kernel/lib.rs

@@ -125,6 +125,8 @@
 pub mod print;
 pub mod processor;
 pub mod ptr;
+#[cfg(CONFIG_RUST_PWM_ABSTRACTIONS)]
+pub mod pwm;
 pub mod rbtree;
 pub mod regulator;
 pub mod revocable;

rust/kernel/pwm.rs

@@ -0,0 +1,735 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2025 Samsung Electronics Co., Ltd.
+// Author: Michal Wilczynski <m.wilczynski@samsung.com>
+
+//! PWM subsystem abstractions.
+//!
+//! C header: [`include/linux/pwm.h`](srctree/include/linux/pwm.h).
+
+use crate::{
+    bindings,
+    container_of,
+    device::{self, Bound},
+    devres,
+    error::{self, to_result},
+    prelude::*,
+    types::{ARef, AlwaysRefCounted, Opaque}, //
+};
+use core::{marker::PhantomData, ptr::NonNull};
+
+/// Represents a PWM waveform configuration.
+/// Mirrors struct [`struct pwm_waveform`](srctree/include/linux/pwm.h).
+#[derive(Copy, Clone, Debug, Default, PartialEq, Eq)]
+pub struct Waveform {
+    /// Total duration of one complete PWM cycle, in nanoseconds.
+    pub period_length_ns: u64,
+
+    /// Duty-cycle active time, in nanoseconds.
+    ///
+    /// For a typical normal polarity configuration (active-high) this is the
+    /// high time of the signal.
+    pub duty_length_ns: u64,
+
+    /// Duty-cycle start offset, in nanoseconds.
+    ///
+    /// Delay from the beginning of the period to the first active edge.
+    /// In most simple PWM setups this is `0`, so the duty cycle starts
+    /// immediately at each period’s start.
+    pub duty_offset_ns: u64,
+}
+
+impl From<bindings::pwm_waveform> for Waveform {
+    fn from(wf: bindings::pwm_waveform) -> Self {
+        Waveform {
+            period_length_ns: wf.period_length_ns,
+            duty_length_ns: wf.duty_length_ns,
+            duty_offset_ns: wf.duty_offset_ns,
+        }
+    }
+}
+
+impl From<Waveform> for bindings::pwm_waveform {
+    fn from(wf: Waveform) -> Self {
+        bindings::pwm_waveform {
+            period_length_ns: wf.period_length_ns,
+            duty_length_ns: wf.duty_length_ns,
+            duty_offset_ns: wf.duty_offset_ns,
+        }
+    }
+}
+
+/// Describes the outcome of a `round_waveform` operation.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum RoundingOutcome {
+    /// The requested waveform was achievable exactly or by rounding values down.
+    ExactOrRoundedDown,
+
+    /// The requested waveform could only be achieved by rounding up.
+    RoundedUp,
+}
+
+/// Wrapper for a PWM device [`struct pwm_device`](srctree/include/linux/pwm.h).
+#[repr(transparent)]
+pub struct Device(Opaque<bindings::pwm_device>);
+
+impl Device {
+    /// Creates a reference to a [`Device`] from a valid C pointer.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid and remains valid for the lifetime of the
+    /// returned [`Device`] reference.
+    pub(crate) unsafe fn from_raw<'a>(ptr: *mut bindings::pwm_device) -> &'a Self {
+        // SAFETY: The safety requirements guarantee the validity of the dereference, while the
+        // `Device` type being transparent makes the cast ok.
+        unsafe { &*ptr.cast::<Self>() }
+    }
+
+    /// Returns a raw pointer to the underlying `pwm_device`.
+    fn as_raw(&self) -> *mut bindings::pwm_device {
+        self.0.get()
+    }
+
+    /// Gets the hardware PWM index for this device within its chip.
+    pub fn hwpwm(&self) -> u32 {
+        // SAFETY: `self.as_raw()` provides a valid pointer for `self`'s lifetime.
+        unsafe { (*self.as_raw()).hwpwm }
+    }
+
+    /// Gets a reference to the parent `Chip` that this device belongs to.
+    pub fn chip<T: PwmOps>(&self) -> &Chip<T> {
+        // SAFETY: `self.as_raw()` provides a valid pointer. (*self.as_raw()).chip
+        // is assumed to be a valid pointer to `pwm_chip` managed by the kernel.
+        // Chip::from_raw's safety conditions must be met.
+        unsafe { Chip::<T>::from_raw((*self.as_raw()).chip) }
+    }
+
+    /// Gets the label for this PWM device, if any.
+    pub fn label(&self) -> Option<&CStr> {
+        // SAFETY: self.as_raw() provides a valid pointer.
+        let label_ptr = unsafe { (*self.as_raw()).label };
+        if label_ptr.is_null() {
+            return None;
+        }
+
+        // SAFETY: label_ptr is non-null and points to a C string
+        // managed by the kernel, valid for the lifetime of the PWM device.
+        Some(unsafe { CStr::from_char_ptr(label_ptr) })
+    }
+
+    /// Sets the PWM waveform configuration and enables the PWM signal.
+    pub fn set_waveform(&self, wf: &Waveform, exact: bool) -> Result {
+        let c_wf = bindings::pwm_waveform::from(*wf);
+
+        // SAFETY: `self.as_raw()` provides a valid `*mut pwm_device` pointer.
+        // `&c_wf` is a valid pointer to a `pwm_waveform` struct. The C function
+        // handles all necessary internal locking.
+        let ret = unsafe { bindings::pwm_set_waveform_might_sleep(self.as_raw(), &c_wf, exact) };
+        to_result(ret)
+    }
+
+    /// Queries the hardware for the configuration it would apply for a given
+    /// request.
+    pub fn round_waveform(&self, wf: &mut Waveform) -> Result<RoundingOutcome> {
+        let mut c_wf = bindings::pwm_waveform::from(*wf);
+
+        // SAFETY: `self.as_raw()` provides a valid `*mut pwm_device` pointer.
+        // `&mut c_wf` is a valid pointer to a mutable `pwm_waveform` struct that
+        // the C function will update.
+        let ret = unsafe { bindings::pwm_round_waveform_might_sleep(self.as_raw(), &mut c_wf) };
+
+        to_result(ret)?;
+
+        *wf = Waveform::from(c_wf);
+
+        if ret == 1 {
+            Ok(RoundingOutcome::RoundedUp)
+        } else {
+            Ok(RoundingOutcome::ExactOrRoundedDown)
+        }
+    }
+
+    /// Reads the current waveform configuration directly from the hardware.
+    pub fn get_waveform(&self) -> Result<Waveform> {
+        let mut c_wf = bindings::pwm_waveform::default();
+
+        // SAFETY: `self.as_raw()` is a valid pointer. We provide a valid pointer
+        // to a stack-allocated `pwm_waveform` struct for the kernel to fill.
+        let ret = unsafe { bindings::pwm_get_waveform_might_sleep(self.as_raw(), &mut c_wf) };
+
+        to_result(ret)?;
+
+        Ok(Waveform::from(c_wf))
+    }
+}
+
+/// The result of a `round_waveform_tohw` operation.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct RoundedWaveform<WfHw> {
+    /// A status code, 0 for success or 1 if values were rounded up.
+    pub status: c_int,
+    /// The driver-specific hardware representation of the waveform.
+    pub hardware_waveform: WfHw,
+}
+
+/// Trait defining the operations for a PWM driver.
+pub trait PwmOps: 'static + Sized {
+    /// The driver-specific hardware representation of a waveform.
+    ///
+    /// This type must be [`Copy`], [`Default`], and fit within `PWM_WFHWSIZE`.
+    type WfHw: Copy + Default;
+
+    /// Optional hook for when a PWM device is requested.
+    fn request(_chip: &Chip<Self>, _pwm: &Device, _parent_dev: &device::Device<Bound>) -> Result {
+        Ok(())
+    }
+
+    /// Optional hook for capturing a PWM signal.
+    fn capture(
+        _chip: &Chip<Self>,
+        _pwm: &Device,
+        _result: &mut bindings::pwm_capture,
+        _timeout: usize,
+        _parent_dev: &device::Device<Bound>,
+    ) -> Result {
+        Err(ENOTSUPP)
+    }
+
+    /// Convert a generic waveform to the hardware-specific representation.
+    /// This is typically a pure calculation and does not perform I/O.
+    fn round_waveform_tohw(
+        _chip: &Chip<Self>,
+        _pwm: &Device,
+        _wf: &Waveform,
+    ) -> Result<RoundedWaveform<Self::WfHw>> {
+        Err(ENOTSUPP)
+    }
+
+    /// Convert a hardware-specific representation back to a generic waveform.
+    /// This is typically a pure calculation and does not perform I/O.
+    fn round_waveform_fromhw(
+        _chip: &Chip<Self>,
+        _pwm: &Device,
+        _wfhw: &Self::WfHw,
+        _wf: &mut Waveform,
+    ) -> Result {
+        Err(ENOTSUPP)
+    }
+
+    /// Read the current hardware configuration into the hardware-specific representation.
+    fn read_waveform(
+        _chip: &Chip<Self>,
+        _pwm: &Device,
+        _parent_dev: &device::Device<Bound>,
+    ) -> Result<Self::WfHw> {
+        Err(ENOTSUPP)
+    }
+
+    /// Write a hardware-specific waveform configuration to the hardware.
+    fn write_waveform(
+        _chip: &Chip<Self>,
+        _pwm: &Device,
+        _wfhw: &Self::WfHw,
+        _parent_dev: &device::Device<Bound>,
+    ) -> Result {
+        Err(ENOTSUPP)
+    }
+}
+
+/// Bridges Rust `PwmOps` to the C `pwm_ops` vtable.
+struct Adapter<T: PwmOps> {
+    _p: PhantomData<T>,
+}
+
+impl<T: PwmOps> Adapter<T> {
+    const VTABLE: PwmOpsVTable = create_pwm_ops::<T>();
+
+    /// # Safety
+    ///
+    /// `wfhw_ptr` must be valid for writes of `size_of::<T::WfHw>()` bytes.
+    unsafe fn serialize_wfhw(wfhw: &T::WfHw, wfhw_ptr: *mut c_void) -> Result {
+        let size = core::mem::size_of::<T::WfHw>();
+
+        build_assert!(size <= bindings::PWM_WFHWSIZE as usize);
+
+        // SAFETY: The caller ensures `wfhw_ptr` is valid for `size` bytes.
+        unsafe {
+            core::ptr::copy_nonoverlapping(
+                core::ptr::from_ref::<T::WfHw>(wfhw).cast::<u8>(),
+                wfhw_ptr.cast::<u8>(),
+                size,
+            );
+        }
+
+        Ok(())
+    }
+
+    /// # Safety
+    ///
+    /// `wfhw_ptr` must be valid for reads of `size_of::<T::WfHw>()` bytes.
+    unsafe fn deserialize_wfhw(wfhw_ptr: *const c_void) -> Result<T::WfHw> {
+        let size = core::mem::size_of::<T::WfHw>();
+
+        build_assert!(size <= bindings::PWM_WFHWSIZE as usize);
+
+        let mut wfhw = T::WfHw::default();
+        // SAFETY: The caller ensures `wfhw_ptr` is valid for `size` bytes.
+        unsafe {
+            core::ptr::copy_nonoverlapping(
+                wfhw_ptr.cast::<u8>(),
+                core::ptr::from_mut::<T::WfHw>(&mut wfhw).cast::<u8>(),
+                size,
+            );
+        }
+
+        Ok(wfhw)
+    }
+
+    /// # Safety
+    ///
+    /// `dev` must be a valid pointer to a `bindings::device` embedded within a
+    /// `bindings::pwm_chip`. This function is called by the device core when the
+    /// last reference to the device is dropped.
+    unsafe extern "C" fn release_callback(dev: *mut bindings::device) {
+        // SAFETY: The function's contract guarantees that `dev` points to a `device`
+        // field embedded within a valid `pwm_chip`. `container_of!` can therefore
+        // safely calculate the address of the containing struct.
+        let c_chip_ptr = unsafe { container_of!(dev, bindings::pwm_chip, dev) };
+
+        // SAFETY: `c_chip_ptr` is a valid pointer to a `pwm_chip` as established
+        // above. Calling this FFI function is safe.
+        let drvdata_ptr = unsafe { bindings::pwmchip_get_drvdata(c_chip_ptr) };
+
+        // SAFETY: The driver data was initialized in `new`. We run its destructor here.
+        unsafe { core::ptr::drop_in_place(drvdata_ptr.cast::<T>()) };
+
+        // Now, call the original release function to free the `pwm_chip` itself.
+        // SAFETY: `dev` is the valid pointer passed into this callback, which is
+        // the expected argument for `pwmchip_release`.
+        unsafe {
+            bindings::pwmchip_release(dev);
+        }
+    }
+
+    /// # Safety
+    ///
+    /// Pointers from C must be valid.
+    unsafe extern "C" fn request_callback(
+        chip_ptr: *mut bindings::pwm_chip,
+        pwm_ptr: *mut bindings::pwm_device,
+    ) -> c_int {
+        // SAFETY: PWM core guarentees `chip_ptr` and `pwm_ptr` are valid pointers.
+        let (chip, pwm) = unsafe { (Chip::<T>::from_raw(chip_ptr), Device::from_raw(pwm_ptr)) };
+
+        // SAFETY: The PWM core guarantees the parent device exists and is bound during callbacks.
+        let bound_parent = unsafe { chip.bound_parent_device() };
+        match T::request(chip, pwm, bound_parent) {
+            Ok(()) => 0,
+            Err(e) => e.to_errno(),
+        }
+    }
+
+    /// # Safety
+    ///
+    /// Pointers from C must be valid.
+    unsafe extern "C" fn capture_callback(
+        chip_ptr: *mut bindings::pwm_chip,
+        pwm_ptr: *mut bindings::pwm_device,
+        res: *mut bindings::pwm_capture,
+        timeout: usize,
+    ) -> c_int {
+        // SAFETY: Relies on the function's contract that `chip_ptr` and `pwm_ptr` are valid
+        // pointers.
+        let (chip, pwm, result) = unsafe {
+            (
+                Chip::<T>::from_raw(chip_ptr),
+                Device::from_raw(pwm_ptr),
+                &mut *res,
+            )
+        };
+
+        // SAFETY: The PWM core guarantees the parent device exists and is bound during callbacks.
+        let bound_parent = unsafe { chip.bound_parent_device() };
+        match T::capture(chip, pwm, result, timeout, bound_parent) {
+            Ok(()) => 0,
+            Err(e) => e.to_errno(),
+        }
+    }
+
+    /// # Safety
+    ///
+    /// Pointers from C must be valid.
+    unsafe extern "C" fn round_waveform_tohw_callback(
+        chip_ptr: *mut bindings::pwm_chip,
+        pwm_ptr: *mut bindings::pwm_device,
+        wf_ptr: *const bindings::pwm_waveform,
+        wfhw_ptr: *mut c_void,
+    ) -> c_int {
+        // SAFETY: Relies on the function's contract that `chip_ptr` and `pwm_ptr` are valid
+        // pointers.
+        let (chip, pwm, wf) = unsafe {
+            (
+                Chip::<T>::from_raw(chip_ptr),
+                Device::from_raw(pwm_ptr),
+                Waveform::from(*wf_ptr),
+            )
+        };
+        match T::round_waveform_tohw(chip, pwm, &wf) {
+            Ok(rounded) => {
+                // SAFETY: `wfhw_ptr` is valid per this function's safety contract.
+                if unsafe { Self::serialize_wfhw(&rounded.hardware_waveform, wfhw_ptr) }.is_err() {
+                    return EINVAL.to_errno();
+                }
+                rounded.status
+            }
+            Err(e) => e.to_errno(),
+        }
+    }
+
+    /// # Safety
+    ///
+    /// Pointers from C must be valid.
+    unsafe extern "C" fn round_waveform_fromhw_callback(
+        chip_ptr: *mut bindings::pwm_chip,
+        pwm_ptr: *mut bindings::pwm_device,
+        wfhw_ptr: *const c_void,
+        wf_ptr: *mut bindings::pwm_waveform,
+    ) -> c_int {
+        // SAFETY: Relies on the function's contract that `chip_ptr` and `pwm_ptr` are valid
+        // pointers.
+        let (chip, pwm) = unsafe { (Chip::<T>::from_raw(chip_ptr), Device::from_raw(pwm_ptr)) };
+        // SAFETY: `deserialize_wfhw`'s safety contract is met by this function's contract.
+        let wfhw = match unsafe { Self::deserialize_wfhw(wfhw_ptr) } {
+            Ok(v) => v,
+            Err(e) => return e.to_errno(),
+        };
+
+        let mut rust_wf = Waveform::default();
+        match T::round_waveform_fromhw(chip, pwm, &wfhw, &mut rust_wf) {
+            Ok(()) => {
+                // SAFETY: `wf_ptr` is guaranteed valid by the C caller.
+                unsafe {
+                    *wf_ptr = rust_wf.into();
+                };
+                0
+            }
+            Err(e) => e.to_errno(),
+        }
+    }
+
+    /// # Safety
+    ///
+    /// Pointers from C must be valid.
+    unsafe extern "C" fn read_waveform_callback(
+        chip_ptr: *mut bindings::pwm_chip,
+        pwm_ptr: *mut bindings::pwm_device,
+        wfhw_ptr: *mut c_void,
+    ) -> c_int {
+        // SAFETY: Relies on the function's contract that `chip_ptr` and `pwm_ptr` are valid
+        // pointers.
+        let (chip, pwm) = unsafe { (Chip::<T>::from_raw(chip_ptr), Device::from_raw(pwm_ptr)) };
+
+        // SAFETY: The PWM core guarantees the parent device exists and is bound during callbacks.
+        let bound_parent = unsafe { chip.bound_parent_device() };
+        match T::read_waveform(chip, pwm, bound_parent) {
+            // SAFETY: `wfhw_ptr` is valid per this function's safety contract.
+            Ok(wfhw) => match unsafe { Self::serialize_wfhw(&wfhw, wfhw_ptr) } {
+                Ok(()) => 0,
+                Err(e) => e.to_errno(),
+            },
+            Err(e) => e.to_errno(),
+        }
+    }
+
+    /// # Safety
+    ///
+    /// Pointers from C must be valid.
+    unsafe extern "C" fn write_waveform_callback(
+        chip_ptr: *mut bindings::pwm_chip,
+        pwm_ptr: *mut bindings::pwm_device,
+        wfhw_ptr: *const c_void,
+    ) -> c_int {
+        // SAFETY: Relies on the function's contract that `chip_ptr` and `pwm_ptr` are valid
+        // pointers.
+        let (chip, pwm) = unsafe { (Chip::<T>::from_raw(chip_ptr), Device::from_raw(pwm_ptr)) };
+
+        // SAFETY: The PWM core guarantees the parent device exists and is bound during callbacks.
+        let bound_parent = unsafe { chip.bound_parent_device() };
+
+        // SAFETY: `wfhw_ptr` is valid per this function's safety contract.
+        let wfhw = match unsafe { Self::deserialize_wfhw(wfhw_ptr) } {
+            Ok(v) => v,
+            Err(e) => return e.to_errno(),
+        };
+        match T::write_waveform(chip, pwm, &wfhw, bound_parent) {
+            Ok(()) => 0,
+            Err(e) => e.to_errno(),
+        }
+    }
+}
+
+/// VTable structure wrapper for PWM operations.
+/// Mirrors [`struct pwm_ops`](srctree/include/linux/pwm.h).
+#[repr(transparent)]
+pub struct PwmOpsVTable(bindings::pwm_ops);
+
+// SAFETY: PwmOpsVTable is Send. The vtable contains only function pointers
+// and a size, which are simple data types that can be safely moved across
+// threads. The thread-safety of calling these functions is handled by the
+// kernel's locking mechanisms.
+unsafe impl Send for PwmOpsVTable {}
+
+// SAFETY: PwmOpsVTable is Sync. The vtable is immutable after it is created,
+// so it can be safely referenced and accessed concurrently by multiple threads
+// e.g. to read the function pointers.
+unsafe impl Sync for PwmOpsVTable {}
+
+impl PwmOpsVTable {
+    /// Returns a raw pointer to the underlying `pwm_ops` struct.
+    pub(crate) fn as_raw(&self) -> *const bindings::pwm_ops {
+        &self.0
+    }
+}
+
+/// Creates a PWM operations vtable for a type `T` that implements `PwmOps`.
+///
+/// This is used to bridge Rust trait implementations to the C `struct pwm_ops`
+/// expected by the kernel.
+pub const fn create_pwm_ops<T: PwmOps>() -> PwmOpsVTable {
+    // SAFETY: `core::mem::zeroed()` is unsafe. For `pwm_ops`, all fields are
+    // `Option<extern "C" fn(...)>` or data, so a zeroed pattern (None/0) is valid initially.
+    let mut ops: bindings::pwm_ops = unsafe { core::mem::zeroed() };
+
+    ops.request = Some(Adapter::<T>::request_callback);
+    ops.capture = Some(Adapter::<T>::capture_callback);
+
+    ops.round_waveform_tohw = Some(Adapter::<T>::round_waveform_tohw_callback);
+    ops.round_waveform_fromhw = Some(Adapter::<T>::round_waveform_fromhw_callback);
+    ops.read_waveform = Some(Adapter::<T>::read_waveform_callback);
+    ops.write_waveform = Some(Adapter::<T>::write_waveform_callback);
+    ops.sizeof_wfhw = core::mem::size_of::<T::WfHw>();
+
+    PwmOpsVTable(ops)
+}
+
+/// Wrapper for a PWM chip/controller ([`struct pwm_chip`](srctree/include/linux/pwm.h)).
+#[repr(transparent)]
+pub struct Chip<T: PwmOps>(Opaque<bindings::pwm_chip>, PhantomData<T>);
+
+impl<T: PwmOps> Chip<T> {
+    /// Creates a reference to a [`Chip`] from a valid pointer.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` is valid and remains valid for the lifetime of the
+    /// returned [`Chip`] reference.
+    pub(crate) unsafe fn from_raw<'a>(ptr: *mut bindings::pwm_chip) -> &'a Self {
+        // SAFETY: The safety requirements guarantee the validity of the dereference, while the
+        // `Chip` type being transparent makes the cast ok.
+        unsafe { &*ptr.cast::<Self>() }
+    }
+
+    /// Returns a raw pointer to the underlying `pwm_chip`.
+    pub(crate) fn as_raw(&self) -> *mut bindings::pwm_chip {
+        self.0.get()
+    }
+
+    /// Gets the number of PWM channels (hardware PWMs) on this chip.
+    pub fn num_channels(&self) -> u32 {
+        // SAFETY: `self.as_raw()` provides a valid pointer for `self`'s lifetime.
+        unsafe { (*self.as_raw()).npwm }
+    }
+
+    /// Returns `true` if the chip supports atomic operations for configuration.
+    pub fn is_atomic(&self) -> bool {
+        // SAFETY: `self.as_raw()` provides a valid pointer for `self`'s lifetime.
+        unsafe { (*self.as_raw()).atomic }
+    }
+
+    /// Returns a reference to the embedded `struct device` abstraction.
+    pub fn device(&self) -> &device::Device {
+        // SAFETY:
+        // - `self.as_raw()` provides a valid pointer to `bindings::pwm_chip`.
+        // - The `dev` field is an instance of `bindings::device` embedded
+        //   within `pwm_chip`.
+        // - Taking a pointer to this embedded field is valid.
+        // - `device::Device` is `#[repr(transparent)]`.
+        // - The lifetime of the returned reference is tied to `self`.
+        unsafe { device::Device::from_raw(&raw mut (*self.as_raw()).dev) }
+    }
+
+    /// Gets the typed driver specific data associated with this chip's embedded device.
+    pub fn drvdata(&self) -> &T {
+        // SAFETY: `pwmchip_get_drvdata` returns the pointer to the private data area,
+        // which we know holds our `T`. The pointer is valid for the lifetime of `self`.
+        unsafe { &*bindings::pwmchip_get_drvdata(self.as_raw()).cast::<T>() }
+    }
+
+    /// Returns a reference to the parent device of this PWM chip's device.
+    ///
+    /// # Safety
+    ///
+    /// The caller must guarantee that the parent device exists and is bound.
+    /// This is guaranteed by the PWM core during `PwmOps` callbacks.
+    unsafe fn bound_parent_device(&self) -> &device::Device<Bound> {
+        // SAFETY: Per the function's safety contract, the parent device exists.
+        let parent = unsafe { self.device().parent().unwrap_unchecked() };
+
+        // SAFETY: Per the function's safety contract, the parent device is bound.
+        // This is guaranteed by the PWM core during `PwmOps` callbacks.
+        unsafe { parent.as_bound() }
+    }
+
+    /// Allocates and wraps a PWM chip using `bindings::pwmchip_alloc`.
+    ///
+    /// Returns an [`ARef<Chip>`] managing the chip's lifetime via refcounting
+    /// on its embedded `struct device`.
+    pub fn new(
+        parent_dev: &device::Device,
+        num_channels: u32,
+        data: impl pin_init::PinInit<T, Error>,
+    ) -> Result<ARef<Self>> {
+        let sizeof_priv = core::mem::size_of::<T>();
+        // SAFETY: `pwmchip_alloc` allocates memory for the C struct and our private data.
+        let c_chip_ptr_raw =
+            unsafe { bindings::pwmchip_alloc(parent_dev.as_raw(), num_channels, sizeof_priv) };
+
+        let c_chip_ptr: *mut bindings::pwm_chip = error::from_err_ptr(c_chip_ptr_raw)?;
+
+        // SAFETY: The `drvdata` pointer is the start of the private area, which is where
+        // we will construct our `T` object.
+        let drvdata_ptr = unsafe { bindings::pwmchip_get_drvdata(c_chip_ptr) };
+
+        // SAFETY: We construct the `T` object in-place in the allocated private memory.
+        unsafe { data.__pinned_init(drvdata_ptr.cast())? };
+
+        // SAFETY: `c_chip_ptr` points to a valid chip.
+        unsafe {
+            (*c_chip_ptr).dev.release = Some(Adapter::<T>::release_callback);
+        }
+
+        // SAFETY: `c_chip_ptr` points to a valid chip.
+        // The `Adapter`'s `VTABLE` has a 'static lifetime, so the pointer
+        // returned by `as_raw()` is always valid.
+        unsafe {
+            (*c_chip_ptr).ops = Adapter::<T>::VTABLE.as_raw();
+        }
+
+        // Cast the `*mut bindings::pwm_chip` to `*mut Chip`. This is valid because
+        // `Chip` is `repr(transparent)` over `Opaque<bindings::pwm_chip>`, and
+        // `Opaque<T>` is `repr(transparent)` over `T`.
+        let chip_ptr_as_self = c_chip_ptr.cast::<Self>();
+
+        // SAFETY: `chip_ptr_as_self` points to a valid `Chip` (layout-compatible with
+        // `bindings::pwm_chip`) whose embedded device has refcount 1.
+        // `ARef::from_raw` takes this pointer and manages it via `AlwaysRefCounted`.
+        Ok(unsafe { ARef::from_raw(NonNull::new_unchecked(chip_ptr_as_self)) })
+    }
+}
+
+// SAFETY: Implements refcounting for `Chip` using the embedded `struct device`.
+unsafe impl<T: PwmOps> AlwaysRefCounted for Chip<T> {
+    #[inline]
+    fn inc_ref(&self) {
+        // SAFETY: `self.0.get()` points to a valid `pwm_chip` because `self` exists.
+        // The embedded `dev` is valid. `get_device` increments its refcount.
+        unsafe {
+            bindings::get_device(&raw mut (*self.0.get()).dev);
+        }
+    }
+
+    #[inline]
+    unsafe fn dec_ref(obj: NonNull<Chip<T>>) {
+        let c_chip_ptr = obj.cast::<bindings::pwm_chip>().as_ptr();
+
+        // SAFETY: `obj` is a valid pointer to a `Chip` (and thus `bindings::pwm_chip`)
+        // with a non-zero refcount. `put_device` handles decrement and final release.
+        unsafe {
+            bindings::put_device(&raw mut (*c_chip_ptr).dev);
+        }
+    }
+}
+
+// SAFETY: `Chip` is a wrapper around `*mut bindings::pwm_chip`. The underlying C
+// structure's state is managed and synchronized by the kernel's device model
+// and PWM core locking mechanisms. Therefore, it is safe to move the `Chip`
+// wrapper (and the pointer it contains) across threads.
+unsafe impl<T: PwmOps + Send> Send for Chip<T> {}
+
+// SAFETY: It is safe for multiple threads to have shared access (`&Chip`) because
+// the `Chip` data is immutable from the Rust side without holding the appropriate
+// kernel locks, which the C core is responsible for. Any interior mutability is
+// handled and synchronized by the C kernel code.
+unsafe impl<T: PwmOps + Sync> Sync for Chip<T> {}
+
+/// A resource guard that ensures `pwmchip_remove` is called on drop.
+///
+/// This struct is intended to be managed by the `devres` framework by transferring its ownership
+/// via [`devres::register`]. This ties the lifetime of the PWM chip registration
+/// to the lifetime of the underlying device.
+pub struct Registration<T: PwmOps> {
+    chip: ARef<Chip<T>>,
+}
+
+impl<T: 'static + PwmOps + Send + Sync> Registration<T> {
+    /// Registers a PWM chip with the PWM subsystem.
+    ///
+    /// Transfers its ownership to the `devres` framework, which ties its lifetime
+    /// to the parent device.
+    /// On unbind of the parent device, the `devres` entry will be dropped, automatically
+    /// calling `pwmchip_remove`. This function should be called from the driver's `probe`.
+    pub fn register(dev: &device::Device<Bound>, chip: ARef<Chip<T>>) -> Result {
+        let chip_parent = chip.device().parent().ok_or(EINVAL)?;
+        if dev.as_raw() != chip_parent.as_raw() {
+            return Err(EINVAL);
+        }
+
+        let c_chip_ptr = chip.as_raw();
+
+        // SAFETY: `c_chip_ptr` points to a valid chip with its ops initialized.
+        // `__pwmchip_add` is the C function to register the chip with the PWM core.
+        unsafe {
+            to_result(bindings::__pwmchip_add(c_chip_ptr, core::ptr::null_mut()))?;
+        }
+
+        let registration = Registration { chip };
+
+        devres::register(dev, registration, GFP_KERNEL)
+    }
+}
+
+impl<T: PwmOps> Drop for Registration<T> {
+    fn drop(&mut self) {
+        let chip_raw = self.chip.as_raw();
+
+        // SAFETY: `chip_raw` points to a chip that was successfully registered.
+        // `bindings::pwmchip_remove` is the correct C function to unregister it.
+        // This `drop` implementation is called automatically by `devres` on driver unbind.
+        unsafe {
+            bindings::pwmchip_remove(chip_raw);
+        }
+    }
+}
+
+/// Declares a kernel module that exposes a single PWM driver.
+///
+/// # Examples
+///
+///```ignore
+/// kernel::module_pwm_platform_driver! {
+///     type: MyDriver,
+///     name: "Module name",
+///     authors: ["Author name"],
+///     description: "Description",
+///     license: "GPL v2",
+/// }
+///```
+#[macro_export]
+macro_rules! module_pwm_platform_driver {
+    ($($user_args:tt)*) => {
+        $crate::module_platform_driver! {
+            $($user_args)*
+            imports_ns: ["PWM"],
+        }
+    };
+}

rust/macros/module.rs

@@ -98,6 +98,7 @@ struct ModuleInfo {
     description: Option<String>,
     alias: Option<Vec<String>>,
     firmware: Option<Vec<String>>,
+    imports_ns: Option<Vec<String>>,
 }
 
 impl ModuleInfo {
@@ -112,6 +113,7 @@ fn parse(it: &mut token_stream::IntoIter) -> Self {
             "license",
             "alias",
             "firmware",
+            "imports_ns",
         ];
         const REQUIRED_KEYS: &[&str] = &["type", "name", "license"];
         let mut seen_keys = Vec::new();
@@ -137,6 +139,7 @@ fn parse(it: &mut token_stream::IntoIter) -> Self {
                 "license" => info.license = expect_string_ascii(it),
                 "alias" => info.alias = Some(expect_string_array(it)),
                 "firmware" => info.firmware = Some(expect_string_array(it)),
+                "imports_ns" => info.imports_ns = Some(expect_string_array(it)),
                 _ => panic!("Unknown key \"{key}\". Valid keys are: {EXPECTED_KEYS:?}."),
             }
 
@@ -195,6 +198,11 @@ pub(crate) fn module(ts: TokenStream) -> TokenStream {
             modinfo.emit("firmware", &fw);
         }
     }
+    if let Some(imports) = info.imports_ns {
+        for ns in imports {
+            modinfo.emit("import_ns", &ns);
+        }
+    }
 
     // Built-in modules also export the `file` modinfo string.
     let file =