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

[Jani Nikula]

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

BR,
Jani.

> ---
>  drivers/gpu/drm/i915/intel_display.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index cddb0c6..b6164d8e 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -2829,7 +2829,7 @@ static void ironlake_update_primary_plane(struct drm_crtc *crtc,
>  	int pixel_size;
>  
>  	if (!visible || !fb) {
> -		I915_WRITE(reg, 0);
> +		I915_WRITE(reg, I915_READ(reg) & ~DISPLAY_PLANE_ENABLE);
>  		I915_WRITE(DSPSURF(plane), 0);
>  		POSTING_READ(reg);
>  		return;
> -- 
> 1.9.1
>
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-- 
Jani Nikula, Intel Open Source Technology Center