drm/imagination: Add power domain control

The first supported GPU only used a single power domain so this was
automatically handled by the device runtime.

In order to support multiple power domains, they must be enumerated from
devicetree and linked to both the GPU device and each other to ensure
correct power sequencing at start time.

For all Imagination Rogue GPUs, power domains are named "a", "b", etc. and
the sequence A->B->... is always valid for startup with the reverse true
for shutdown. Note this is not always the *only* valid sequence, but it's
simple and does not require special-casing for different GPU power
topologies.

Reviewed-by: Frank Binns <frank.binns@imgtec.com>
Link: https://lore.kernel.org/r/20250410-sets-bxs-4-64-patch-v1-v6-5-eda620c5865f@imgtec.com
Signed-off-by: Matt Coster <matt.coster@imgtec.com>

drivers/gpu/drm/imagination/pvr_device.h

@@ -18,6 +18,7 @@
 #include <linux/bits.h>
 #include <linux/compiler_attributes.h>
 #include <linux/compiler_types.h>
+#include <linux/device.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
 #include <linux/kernel.h>
@@ -131,6 +132,13 @@ struct pvr_device {
 	 */
 	struct clk *mem_clk;
 
+	struct pvr_device_power {
+		struct device **domain_devs;
+		struct device_link **domain_links;
+
+		u32 domain_count;
+	} power;
+
 	/** @irq: IRQ number. */
 	int irq;
 

drivers/gpu/drm/imagination/pvr_drv.c

@@ -1411,6 +1411,10 @@ pvr_probe(struct platform_device *plat_dev)
 
 	platform_set_drvdata(plat_dev, drm_dev);
 
+	err = pvr_power_domains_init(pvr_dev);
+	if (err)
+		return err;
+
 	init_rwsem(&pvr_dev->reset_sem);
 
 	pvr_context_device_init(pvr_dev);
@@ -1450,6 +1454,8 @@ pvr_probe(struct platform_device *plat_dev)
 err_context_fini:
 	pvr_context_device_fini(pvr_dev);
 
+	pvr_power_domains_fini(pvr_dev);
+
 	return err;
 }
 
@@ -1470,6 +1476,7 @@ static void pvr_remove(struct platform_device *plat_dev)
 	pvr_watchdog_fini(pvr_dev);
 	pvr_queue_device_fini(pvr_dev);
 	pvr_context_device_fini(pvr_dev);
+	pvr_power_domains_fini(pvr_dev);
 }
 
 static const struct of_device_id dt_match[] = {

drivers/gpu/drm/imagination/pvr_power.c

@@ -10,10 +10,13 @@
 
 #include <drm/drm_drv.h>
 #include <drm/drm_managed.h>
+#include <linux/cleanup.h>
 #include <linux/clk.h>
 #include <linux/interrupt.h>
 #include <linux/mutex.h>
+#include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/pm_domain.h>
 #include <linux/pm_runtime.h>
 #include <linux/timer.h>
 #include <linux/types.h>
@@ -431,3 +434,114 @@ pvr_watchdog_fini(struct pvr_device *pvr_dev)
 {
 	cancel_delayed_work_sync(&pvr_dev->watchdog.work);
 }
+
+int pvr_power_domains_init(struct pvr_device *pvr_dev)
+{
+	struct device *dev = from_pvr_device(pvr_dev)->dev;
+
+	struct device_link **domain_links __free(kfree) = NULL;
+	struct device **domain_devs __free(kfree) = NULL;
+	int domain_count;
+	int link_count;
+
+	char dev_name[2] = "a";
+	int err;
+	int i;
+
+	domain_count = of_count_phandle_with_args(dev->of_node, "power-domains",
+						  "#power-domain-cells");
+	if (domain_count < 0)
+		return domain_count;
+
+	if (domain_count <= 1)
+		return 0;
+
+	link_count = domain_count + (domain_count - 1);
+
+	domain_devs = kcalloc(domain_count, sizeof(*domain_devs), GFP_KERNEL);
+	if (!domain_devs)
+		return -ENOMEM;
+
+	domain_links = kcalloc(link_count, sizeof(*domain_links), GFP_KERNEL);
+	if (!domain_links)
+		return -ENOMEM;
+
+	for (i = 0; i < domain_count; i++) {
+		struct device *domain_dev;
+
+		dev_name[0] = 'a' + i;
+		domain_dev = dev_pm_domain_attach_by_name(dev, dev_name);
+		if (IS_ERR_OR_NULL(domain_dev)) {
+			err = domain_dev ? PTR_ERR(domain_dev) : -ENODEV;
+			goto err_detach;
+		}
+
+		domain_devs[i] = domain_dev;
+	}
+
+	for (i = 0; i < domain_count; i++) {
+		struct device_link *link;
+
+		link = device_link_add(dev, domain_devs[i], DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME);
+		if (!link) {
+			err = -ENODEV;
+			goto err_unlink;
+		}
+
+		domain_links[i] = link;
+	}
+
+	for (i = domain_count; i < link_count; i++) {
+		struct device_link *link;
+
+		link = device_link_add(domain_devs[i - domain_count + 1],
+				       domain_devs[i - domain_count],
+				       DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME);
+		if (!link) {
+			err = -ENODEV;
+			goto err_unlink;
+		}
+
+		domain_links[i] = link;
+	}
+
+	pvr_dev->power = (struct pvr_device_power){
+		.domain_devs = no_free_ptr(domain_devs),
+		.domain_links = no_free_ptr(domain_links),
+		.domain_count = domain_count,
+	};
+
+	return 0;
+
+err_unlink:
+	while (--i >= 0)
+		device_link_del(domain_links[i]);
+
+	i = domain_count;
+
+err_detach:
+	while (--i >= 0)
+		dev_pm_domain_detach(domain_devs[i], true);
+
+	return err;
+}
+
+void pvr_power_domains_fini(struct pvr_device *pvr_dev)
+{
+	const int domain_count = pvr_dev->power.domain_count;
+
+	int i = domain_count + (domain_count - 1);
+
+	while (--i >= 0)
+		device_link_del(pvr_dev->power.domain_links[i]);
+
+	i = domain_count;
+
+	while (--i >= 0)
+		dev_pm_domain_detach(pvr_dev->power.domain_devs[i], true);
+
+	kfree(pvr_dev->power.domain_links);
+	kfree(pvr_dev->power.domain_devs);
+
+	pvr_dev->power = (struct pvr_device_power){ 0 };
+}

drivers/gpu/drm/imagination/pvr_power.h

@@ -38,4 +38,7 @@ pvr_power_put(struct pvr_device *pvr_dev)
 	return pm_runtime_put(drm_dev->dev);
 }
 
+int pvr_power_domains_init(struct pvr_device *pvr_dev);
+void pvr_power_domains_fini(struct pvr_device *pvr_dev);
+
 #endif /* PVR_POWER_H */