drm/ingenic: Add basic PM support

Call drm_mode_config_helper_suspend() and
drm_mode_config_helper_resume() on suspend and resume, respectively.

This makes sure that the display stack is properly disabled when the
hardware is put to sleep.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201128171606.132830-1-paul@crapouillou.net

drivers/gpu/drm/ingenic/ingenic-drm-drv.c

@@ -14,6 +14,7 @@
 #include <linux/of_device.h>
 #include <linux/of_reserved_mem.h>
 #include <linux/platform_device.h>
+#include <linux/pm.h>
 #include <linux/regmap.h>
 
 #include <drm/drm_atomic.h>
@@ -1167,6 +1168,22 @@ static int ingenic_drm_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static int __maybe_unused ingenic_drm_suspend(struct device *dev)
+{
+	struct ingenic_drm *priv = dev_get_drvdata(dev);
+
+	return drm_mode_config_helper_suspend(&priv->drm);
+}
+
+static int __maybe_unused ingenic_drm_resume(struct device *dev)
+{
+	struct ingenic_drm *priv = dev_get_drvdata(dev);
+
+	return drm_mode_config_helper_resume(&priv->drm);
+}
+
+static SIMPLE_DEV_PM_OPS(ingenic_drm_pm_ops, ingenic_drm_suspend, ingenic_drm_resume);
+
 static const u32 jz4740_formats[] = {
 	DRM_FORMAT_XRGB1555,
 	DRM_FORMAT_RGB565,
@@ -1246,6 +1263,7 @@ MODULE_DEVICE_TABLE(of, ingenic_drm_of_match);
 static struct platform_driver ingenic_drm_driver = {
 	.driver = {
 		.name = "ingenic-drm",
+		.pm = pm_ptr(&ingenic_drm_pm_ops),
 		.of_match_table = of_match_ptr(ingenic_drm_of_match),
 	},
 	.probe = ingenic_drm_probe,