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

[Hans de Goede]

And another skylake laptop external monitor fix
which would be good to add to the Fedora kernels.
(note it has a Cc stable)

-------- Forwarded Message --------
Subject: [PATCH] drm/i915/skl: Fix redundant cursor update, fix cursor underruns
Date: Fri, 15 Jul 2016 18:13:56 -0400
From: Lyude 
To: [e-mail]
CC: Lyude , Radhakrishna Sripada , Hans de Goede , [e-mail], Daniel Vetter , Jani Nikula , David Airlie , open list:INTEL DRM DRIVERS (excluding Poulsbo, Moorestow...), [e-mail] (open list)

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 
Cc: Radhakrishna Sripada 
Cc: Hans de Goede 
Cc: [e-mail]
---
  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