drm: renesas: shmobile: Add support for Runtime PM

The SH-Mobile LCD Controller is part of a PM Domain on all relevant SoCs
(clock domain on all, power domain on some).  Hence it may not be
sufficient to manage the LCDC module clock explicitly (e.g. if the
selected clock source differs from SHMOB_DRM_CLK_BUS).

Fix this by using Runtime PM for all clock handling.  Add an explicit
dependency on CONFIG_PM, which should already be met on all affected
platforms.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/e7359a64963bd9a4f1531c2beae850774ce140bc.1694767209.git.geert+renesas@glider.be

drivers/gpu/drm/renesas/shmobile/Kconfig

 # SPDX-License-Identifier: GPL-2.0
 config DRM_SHMOBILE
 	tristate "DRM Support for SH Mobile"
-	depends on DRM
+	depends on DRM && PM
 	depends on ARCH_RENESAS || ARCH_SHMOBILE || COMPILE_TEST
 	select BACKLIGHT_CLASS_DEVICE
 	select DRM_KMS_HELPER

drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.c

@@ -9,6 +9,7 @@
 
 #include <linux/backlight.h>
 #include <linux/clk.h>
+#include <linux/pm_runtime.h>
 
 #include <drm/drm_crtc.h>
 #include <drm/drm_crtc_helper.h>
@@ -34,29 +35,6 @@
  * TODO: panel support
  */
 
-/* -----------------------------------------------------------------------------
- * Clock management
- */
-
-static int shmob_drm_clk_on(struct shmob_drm_device *sdev)
-{
-	int ret;
-
-	if (sdev->clock) {
-		ret = clk_prepare_enable(sdev->clock);
-		if (ret < 0)
-			return ret;
-	}
-
-	return 0;
-}
-
-static void shmob_drm_clk_off(struct shmob_drm_device *sdev)
-{
-	if (sdev->clock)
-		clk_disable_unprepare(sdev->clock);
-}
-
 /* -----------------------------------------------------------------------------
  * CRTC
  */
@@ -170,9 +148,8 @@ static void shmob_drm_crtc_start(struct shmob_drm_crtc *scrtc)
 	if (WARN_ON(format == NULL))
 		return;
 
-	/* Enable clocks before accessing the hardware. */
-	ret = shmob_drm_clk_on(sdev);
-	if (ret < 0)
+	ret = pm_runtime_resume_and_get(sdev->dev);
+	if (ret)
 		return;
 
 	/* Reset and enable the LCDC. */
@@ -268,8 +245,7 @@ static void shmob_drm_crtc_stop(struct shmob_drm_crtc *scrtc)
 	/* Disable the display output. */
 	lcdc_write(sdev, LDCNT1R, 0);
 
-	/* Stop clocks. */
-	shmob_drm_clk_off(sdev);
+	pm_runtime_put(sdev->dev);
 
 	scrtc->started = false;
 }

drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c

@@ -13,6 +13,7 @@
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/pm.h>
+#include <linux/pm_runtime.h>
 #include <linux/slab.h>
 
 #include <drm/drm_drv.h>
@@ -165,8 +166,35 @@ static int shmob_drm_pm_resume(struct device *dev)
 	return 0;
 }
 
-static DEFINE_SIMPLE_DEV_PM_OPS(shmob_drm_pm_ops,
-				shmob_drm_pm_suspend, shmob_drm_pm_resume);
+static int shmob_drm_pm_runtime_suspend(struct device *dev)
+{
+	struct shmob_drm_device *sdev = dev_get_drvdata(dev);
+
+	if (sdev->clock)
+		clk_disable_unprepare(sdev->clock);
+
+	return 0;
+}
+
+static int shmob_drm_pm_runtime_resume(struct device *dev)
+{
+	struct shmob_drm_device *sdev = dev_get_drvdata(dev);
+	int ret;
+
+	if (sdev->clock) {
+		ret = clk_prepare_enable(sdev->clock);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+static const struct dev_pm_ops shmob_drm_pm_ops = {
+	SYSTEM_SLEEP_PM_OPS(shmob_drm_pm_suspend, shmob_drm_pm_resume)
+	RUNTIME_PM_OPS(shmob_drm_pm_runtime_suspend,
+		       shmob_drm_pm_runtime_resume, NULL)
+};
 
 /* -----------------------------------------------------------------------------
  * Platform driver
@@ -218,6 +246,10 @@ static int shmob_drm_probe(struct platform_device *pdev)
 	if (ret < 0)
 		return ret;
 
+	ret = devm_pm_runtime_enable(&pdev->dev);
+	if (ret)
+		return ret;
+
 	ret = shmob_drm_init_interface(sdev);
 	if (ret < 0)
 		return ret;
@@ -289,7 +321,7 @@ static struct platform_driver shmob_drm_platform_driver = {
 	.remove_new	= shmob_drm_remove,
 	.driver		= {
 		.name	= "shmob-drm",
-		.pm	= pm_sleep_ptr(&shmob_drm_pm_ops),
+		.pm	= &shmob_drm_pm_ops,
 	},
 };