soc: renesas: rz-sysc: Add syscon/regmap support

The RZ/G3E system controller has various registers that control or report
some properties specific to individual IPs. The regmap is registered as a
syscon device to allow these IP drivers to access the registers through the
regmap API.

As other RZ SoCs might have custom read/write callbacks or max-offsets,
register a custom regmap configuration.

[claudiu.beznea:
 - do not check the match->data validity in rz_sysc_probe() as it is
   always valid
 - dinamically allocate regmap_cfg]

Signed-off-by: John Madieu <john.madieu.xa@bp.renesas.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Tested-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com> # on RZ/G3S
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20250818162859.9661-2-john.madieu.xa@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

drivers/soc/renesas/Kconfig

@@ -449,6 +449,7 @@ config RST_RCAR
 
 config SYSC_RZ
 	bool "System controller for RZ SoCs" if COMPILE_TEST
+	select MFD_SYSCON
 
 config SYSC_R9A08G045
 	bool "Renesas System controller support for R9A08G045 (RZ/G3S)" if COMPILE_TEST

drivers/soc/renesas/r9a08g045-sysc.c

@@ -20,4 +20,5 @@ static const struct rz_sysc_soc_id_init_data rzg3s_sysc_soc_id_init_data __initc
 
 const struct rz_sysc_init_data rzg3s_sysc_init_data __initconst = {
 	.soc_id_init_data = &rzg3s_sysc_soc_id_init_data,
+	.max_register = 0xe20,
 };

drivers/soc/renesas/r9a09g047-sys.c

@@ -64,4 +64,5 @@ static const struct rz_sysc_soc_id_init_data rzg3e_sys_soc_id_init_data __initco
 
 const struct rz_sysc_init_data rzg3e_sys_init_data = {
 	.soc_id_init_data = &rzg3e_sys_soc_id_init_data,
+	.max_register = 0x170c,
 };

drivers/soc/renesas/r9a09g057-sys.c

@@ -64,4 +64,5 @@ static const struct rz_sysc_soc_id_init_data rzv2h_sys_soc_id_init_data __initco
 
 const struct rz_sysc_init_data rzv2h_sys_init_data = {
 	.soc_id_init_data = &rzv2h_sys_soc_id_init_data,
+	.max_register = 0x170c,
 };

drivers/soc/renesas/rz-sysc.c

@@ -5,9 +5,13 @@
  * Copyright (C) 2024 Renesas Electronics Corp.
  */
 
+#include <linux/cleanup.h>
 #include <linux/io.h>
+#include <linux/mfd/syscon.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
 #include <linux/sys_soc.h>
 
 #include "rz-sysc.h"
@@ -100,14 +104,23 @@ MODULE_DEVICE_TABLE(of, rz_sysc_match);
 
 static int rz_sysc_probe(struct platform_device *pdev)
 {
+	const struct rz_sysc_init_data *data;
 	const struct of_device_id *match;
 	struct device *dev = &pdev->dev;
+	struct regmap *regmap;
 	struct rz_sysc *sysc;
+	int ret;
+
+	struct regmap_config *regmap_cfg __free(kfree) = kzalloc(sizeof(*regmap_cfg), GFP_KERNEL);
+	if (!regmap_cfg)
+		return -ENOMEM;
 
 	match = of_match_node(rz_sysc_match, dev->of_node);
 	if (!match)
 		return -ENODEV;
 
+	data = match->data;
+
 	sysc = devm_kzalloc(dev, sizeof(*sysc), GFP_KERNEL);
 	if (!sysc)
 		return -ENOMEM;
@@ -117,7 +130,22 @@ static int rz_sysc_probe(struct platform_device *pdev)
 		return PTR_ERR(sysc->base);
 
 	sysc->dev = dev;
-	return rz_sysc_soc_init(sysc, match);
+	ret = rz_sysc_soc_init(sysc, match);
+	if (ret)
+		return ret;
+
+	regmap_cfg->name = "rz_sysc_regs";
+	regmap_cfg->reg_bits = 32;
+	regmap_cfg->reg_stride = 4;
+	regmap_cfg->val_bits = 32;
+	regmap_cfg->fast_io = true;
+	regmap_cfg->max_register = data->max_register;
+
+	regmap = devm_regmap_init_mmio(dev, sysc->base, regmap_cfg);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	return of_syscon_register_regmap(dev->of_node, regmap);
 }
 
 static struct platform_driver rz_sysc_driver = {

drivers/soc/renesas/rz-sysc.h

@@ -34,9 +34,11 @@ struct rz_sysc_soc_id_init_data {
 /**
  * struct rz_sysc_init_data - RZ SYSC initialization data
  * @soc_id_init_data: RZ SYSC SoC ID initialization data
+ * @max_register: Maximum SYSC register offset to be used by the regmap config
  */
 struct rz_sysc_init_data {
 	const struct rz_sysc_soc_id_init_data *soc_id_init_data;
+	u32 max_register;
 };
 
 extern const struct rz_sysc_init_data rzg3e_sys_init_data;