[PATCH] drm/i915/skl: Fix redundant cursor update, fix cursor underruns

[Lyude]

At long last, the time has finally come for Skylake users to plug their
external displays back in.

During intel_atomic_commit() on Skylake, we've actually been arming the
registers to update the cursor information twice instead of just once.
Once in i9xx_update_cursor(), and once in skl_wm_flush_pipe(). This
isn't actually necessary, and removing the later update in
skl_wm_flush_pipe() has completely stopped the underruns on this T460p
from occurring when moving the mouse cursor from one monitor to another.

Signed-off-by: Lyude <cpaul at redhat.com>
Cc: Radhakrishna Sripada <radhakrishna.sripada at intel.com>
Cc: Hans de Goede <hdegoede at redhat.com>
Cc: stable at vger.kernel.org
---
 drivers/gpu/drm/i915/intel_pm.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 7ac71ec..4771a03 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3860,7 +3860,6 @@ skl_wm_flush_pipe(struct drm_i915_private *dev_priv, enum pipe pipe, int pass)
 		I915_WRITE(PLANE_SURF(pipe, plane),
 			   I915_READ(PLANE_SURF(pipe, plane)));
 	}
-	I915_WRITE(CURBASE(pipe), I915_READ(CURBASE(pipe)));
 }
 
 static bool
-- 
2.7.4