drm: rcar-du: Implement system suspend/resume support

To support system suspend operations we must ensure the hardware is
stopped, and resumed explicitly from the suspend and resume handlers.

Implement suspend and resume functions using the DRM atomic helper
functions.

Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_drv.c

@@ -22,6 +22,7 @@
 #include <linux/wait.h>
 
 #include <drm/drmP.h>
+#include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_fb_cma_helper.h>
 #include <drm/drm_gem_cma_helper.h>
@@ -309,9 +310,19 @@ static struct drm_driver rcar_du_driver = {
 static int rcar_du_pm_suspend(struct device *dev)
 {
 	struct rcar_du_device *rcdu = dev_get_drvdata(dev);
+	struct drm_atomic_state *state;
 
 	drm_kms_helper_poll_disable(rcdu->ddev);
-	/* TODO Suspend the CRTC */
+	drm_fbdev_cma_set_suspend_unlocked(rcdu->fbdev, true);
+
+	state = drm_atomic_helper_suspend(rcdu->ddev);
+	if (IS_ERR(state)) {
+		drm_fbdev_cma_set_suspend_unlocked(rcdu->fbdev, false);
+		drm_kms_helper_poll_enable(rcdu->ddev);
+		return PTR_ERR(state);
+	}
+
+	rcdu->suspend_state = state;
 
 	return 0;
 }
@@ -320,9 +331,10 @@ static int rcar_du_pm_resume(struct device *dev)
 {
 	struct rcar_du_device *rcdu = dev_get_drvdata(dev);
 
-	/* TODO Resume the CRTC */
-
+	drm_atomic_helper_resume(rcdu->ddev, rcdu->suspend_state);
+	drm_fbdev_cma_set_suspend_unlocked(rcdu->fbdev, false);
 	drm_kms_helper_poll_enable(rcdu->ddev);
+
 	return 0;
 }
 #endif

drivers/gpu/drm/rcar-du/rcar_du_drv.h

@@ -81,6 +81,7 @@ struct rcar_du_device {
 
 	struct drm_device *ddev;
 	struct drm_fbdev_cma *fbdev;
+	struct drm_atomic_state *suspend_state;
 
 	struct rcar_du_crtc crtcs[RCAR_DU_MAX_CRTCS];
 	unsigned int num_crtcs;