drm/msm: call drm_atomic_helper_suspend() and drm_atomic_helper_resume()

To make suspend and resume work on msm8916 platforms, call into the generic
helpers and preserve the state across suspends.
Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_drv.c

@@ -894,16 +894,25 @@ static struct drm_driver msm_driver = {
 static int msm_pm_suspend(struct device *dev)
 {
 	struct drm_device *ddev = dev_get_drvdata(dev);
+	struct msm_drm_private *priv = ddev->dev_private;
 
 	drm_kms_helper_poll_disable(ddev);
 
+	priv->pm_state = drm_atomic_helper_suspend(ddev);
+	if (IS_ERR(priv->pm_state)) {
+		drm_kms_helper_poll_enable(ddev);
+		return PTR_ERR(priv->pm_state);
+	}
+
 	return 0;
 }
 
 static int msm_pm_resume(struct device *dev)
 {
 	struct drm_device *ddev = dev_get_drvdata(dev);
+	struct msm_drm_private *priv = ddev->dev_private;
 
+	drm_atomic_helper_resume(ddev, priv->pm_state);
 	drm_kms_helper_poll_enable(ddev);
 
 	return 0;

drivers/gpu/drm/msm/msm_drv.h

@@ -150,6 +150,7 @@ struct msm_drm_private {
 	struct shrinker shrinker;
 
 	struct msm_vblank_ctrl vblank_ctrl;
+	struct drm_atomic_state *pm_state;
 };
 
 struct msm_format {