FAILED: patch "[PATCH] drm/i915/skl: Update watermarks before the crtc is disabled." failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Maarten Lankhorst <[email protected]>
Date: Thu, 19 Nov 2015 16:07:16 +0100
Subject: [PATCH] drm/i915/skl: Update watermarks before the crtc is disabled.

On skylake some of the registers are only writable when the correct power wells are enabled. Because of this watermarks have to be updated before the crtc turns off, or you get unclaimed register read and write warnings.

This patch needs to be modified slightly to apply to -fixes.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92181

index a8fb7cf0b3e1..f118f7ec4368 100644
@@ -4804,7 +4804,7 @@ static void intel_post_plane_update(struct intel_crtc *crtc)
 
 	crtc->wm.cxsr_allowed = true;
 
-	if (pipe_config->wm_changed)
+	if (pipe_config->wm_changed && pipe_config->base.active)
 		intel_update_watermarks(&crtc->base);
 
 	if (atomic->update_fbc)

@@ -13421,6 +13421,9 @@ static int intel_atomic_commit(struct drm_device *dev,
 			 */
 			intel_check_cpu_fifo_underruns(dev_priv);
 			intel_check_pch_fifo_underruns(dev_priv);
+
+			if (!crtc->state->active)
+				intel_update_watermarks(crtc);
 		}
 	}