[Intel-gfx] [PATCH 1/2] drm/i915: skip the first 4k of stolen memory on everything >= gen8

[Paulo Zanoni]

Em Qua, 2016-12-14 às 12:55 -0200, Paulo Zanoni escreveu:
> BSpec got updated and this workaround is now listed as standard
> required programming for all subsequent projects. This is confirmed
> to
> fix Skylake screen flickering issues (probably caused by the fact
> that
> we initialized a ring in the first page of stolen, but I didn't 100%
> confirm this theory).
> 
> v2: this is the patch that fixes the screen flickering, document it.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94605
> Cc: stable at vger.kernel.org
> Tested-by: Dominik Klementowski <dominik232 at gmail.com>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>

Daniel gave me the missing R-B for this patch on IRC, so I pushed both
patches.

Thanks everybody for the reviews.

> ---
>  drivers/gpu/drm/i915/i915_gem_stolen.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c
> b/drivers/gpu/drm/i915/i915_gem_stolen.c
> index efc0e74..b1c8897 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -55,10 +55,9 @@ int i915_gem_stolen_insert_node_in_range(struct
> drm_i915_private *dev_priv,
>  		return -ENODEV;
>  
>  	/* See the comment at the drm_mm_init() call for more about
> this check.
> -	 * WaSkipStolenMemoryFirstPage:bdw,chv,kbl (incomplete)
> +	 * WaSkipStolenMemoryFirstPage:bdw+ (incomplete)
>  	 */
> -	if (start < 4096 && (IS_GEN8(dev_priv) ||
> -			     IS_KBL_REVID(dev_priv, 0,
> KBL_REVID_A0)))
> +	if (start < 4096 && INTEL_GEN(dev_priv) >= 8)
>  		start = 4096;
>  
>  	mutex_lock(&dev_priv->mm.stolen_lock);