drm/panfrost: Add PM runtime flag

When the GPU is the only device attached to a single power domain,
core genpd disable and enable it when gpu enter and leave runtime suspend.

Some power-domain requires a sequence before disabled,
and the reverse when enabled.

Add GPU_PM_RT flag, and implement in
panfrost_device_runtime_suspend/resume.

Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Philippe Simons <simons.philippe@gmail.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20250403055210.54486-2-simons.philippe@gmail.com

Author: loki666

drivers/gpu/drm/panfrost/panfrost_device.c

@@ -406,11 +406,36 @@ void panfrost_device_reset(struct panfrost_device *pfdev)
 static int panfrost_device_runtime_resume(struct device *dev)
 {
 	struct panfrost_device *pfdev = dev_get_drvdata(dev);
+	int ret;
+
+	if (pfdev->comp->pm_features & BIT(GPU_PM_RT)) {
+		ret = reset_control_deassert(pfdev->rstc);
+		if (ret)
+			return ret;
+
+		ret = clk_enable(pfdev->clock);
+		if (ret)
+			goto err_clk;
+
+		if (pfdev->bus_clock) {
+			ret = clk_enable(pfdev->bus_clock);
+			if (ret)
+				goto err_bus_clk;
+		}
+	}
 
 	panfrost_device_reset(pfdev);
 	panfrost_devfreq_resume(pfdev);
 
 	return 0;
+
+err_bus_clk:
+	if (pfdev->comp->pm_features & BIT(GPU_PM_RT))
+		clk_disable(pfdev->clock);
+err_clk:
+	if (pfdev->comp->pm_features & BIT(GPU_PM_RT))
+		reset_control_assert(pfdev->rstc);
+	return ret;
 }
 
 static int panfrost_device_runtime_suspend(struct device *dev)
@@ -426,6 +451,14 @@ static int panfrost_device_runtime_suspend(struct device *dev)
 	panfrost_gpu_suspend_irq(pfdev);
 	panfrost_gpu_power_off(pfdev);
 
+	if (pfdev->comp->pm_features & BIT(GPU_PM_RT)) {
+		if (pfdev->bus_clock)
+			clk_disable(pfdev->bus_clock);
+
+		clk_disable(pfdev->clock);
+		reset_control_assert(pfdev->rstc);
+	}
+
 	return 0;
 }
 

drivers/gpu/drm/panfrost/panfrost_device.h

@@ -36,10 +36,13 @@ enum panfrost_drv_comp_bits {
  * enum panfrost_gpu_pm - Supported kernel power management features
  * @GPU_PM_CLK_DIS:  Allow disabling clocks during system suspend
  * @GPU_PM_VREG_OFF: Allow turning off regulators during system suspend
+ * @GPU_PM_RT: Allow disabling clocks and asserting the reset control during
+ *  system runtime suspend
  */
 enum panfrost_gpu_pm {
 	GPU_PM_CLK_DIS,
 	GPU_PM_VREG_OFF,
+	GPU_PM_RT
 };
 
 /**