[Intel-gfx] [PATCH] drm/i915: respect previous reg values on primary plane disable

[Kevin Strasser]

On Wed, Oct 14, 2015 at 10:58:29AM +0300, Jani Nikula wrote:
> On Wed, 14 Oct 2015, Kevin Strasser <kevin.strasser at linux.intel.com> wrote:
> > On HSW the crc differs between black and disabled primary planes, causing an
> > assert to fail in the kms_universal_plane test. It seems that things like gamma
> > correction are causing the black primary plane case to result in a brighter
> > color than the disabled primary plane case.
> >
> > Only toggle the enable bit instead of clearing the control register, making the
> > disable path more similar to that of the sprite plane.
> >
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89331
> > Testcase: igt/kms_universal_plane
> > Signed-off-by: Kevin Strasser <kevin.strasser at linux.intel.com>
> 
> Cc: stable at vger.kernel.org # v3.18
> Fixes: fdd508a64192 ("drm/i915: Call .update_primary_plane in intel_{enable, disable}_primary_hw_plane()")
> 
> How about i9xx_update_primary_plane, modified in the same commit above,
> and skylake_update_primary_plane, added in
> 
> commit 6156a45602f990cdb140025a3ced96e6695980cf
> Author: Chandra Konduru <chandra.konduru at intel.com>
> Date:   Mon Apr 27 13:48:39 2015 -0700
> 
>     drm/i915: skylake primary plane scaling using shared scalers

Afaict HSW is the only platform that behaves in this way. I will follow up with
a separate patch if needed.

Thanks,
Kevin