[Intel-gfx] [PATCH] drm/i915/gt: Temporarily force MTL into uncached mode

[Matt Roper]

On Mon, Oct 09, 2023 at 04:38:56PM -0700, Jonathan Cavitt wrote:
> FIXME: CAT errors are cropping up on MTL.  This removes them,
> but the real root cause must still be diagnosed.

Do you have a link to specific IGT test(s) that illustrate the CAT
errors so that we can ensure that they now appear fixed in CI?


Matt

> 
> Signed-off-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_gt.c     | 6 +++++-
>  drivers/gpu/drm/i915/gt/intel_lrc.c    | 5 ++++-
>  drivers/gpu/drm/i915/gt/uc/intel_guc.c | 5 ++++-
>  3 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index ed32bf5b15464..b52c8eb0b033f 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -1026,8 +1026,12 @@ enum i915_map_type intel_gt_coherent_map_type(struct intel_gt *gt,
>  	/*
>  	 * Wa_22016122933: always return I915_MAP_WC for Media
>  	 * version 13.0 when the object is on the Media GT
> +	 *
> +	 * FIXME: CAT errors are cropping up on MTL.  This removes them,
> +	 * but the real root cause must still be diagnosed.
>  	 */
> -	if (i915_gem_object_is_lmem(obj) || intel_gt_needs_wa_22016122933(gt))
> +	if (i915_gem_object_is_lmem(obj) || intel_gt_needs_wa_22016122933(gt) ||
> +	    IS_METEORLAKE(gt->i915))
>  		return I915_MAP_WC;
>  	if (HAS_LLC(gt->i915) || always_coherent)
>  		return I915_MAP_WB;
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index eaf66d9031665..8aaa4df84cb3e 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -1124,8 +1124,11 @@ __lrc_alloc_state(struct intel_context *ce, struct intel_engine_cs *engine)
>  		 * Wa_22016122933: For Media version 13.0, all Media GT shared
>  		 * memory needs to be mapped as WC on CPU side and UC (PAT
>  		 * index 2) on GPU side.
> +		 *
> +		 * FIXME: CAT errors are cropping up on MTL.  This removes them,
> +		 * but the real root cause must still be diagnosed.
>  		 */
> -		if (intel_gt_needs_wa_22016122933(engine->gt))
> +		if (intel_gt_needs_wa_22016122933(engine->gt) || IS_METEORLAKE(engine->i915))
>  			i915_gem_object_set_cache_coherency(obj, I915_CACHE_NONE);
>  	}
>  
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.c b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> index 27df41c53b890..e3a7d61506188 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> @@ -774,8 +774,11 @@ struct i915_vma *intel_guc_allocate_vma(struct intel_guc *guc, u32 size)
>  	 * Wa_22016122933: For Media version 13.0, all Media GT shared
>  	 * memory needs to be mapped as WC on CPU side and UC (PAT
>  	 * index 2) on GPU side.
> +	 *
> +	 * FIXME: CAT errors are cropping up on MTL.  This removes them,
> +	 * but the real root cause must still be diagnosed.
>  	 */
> -	if (intel_gt_needs_wa_22016122933(gt))
> +	if (intel_gt_needs_wa_22016122933(gt) || IS_METEORLAKE(gt->i915))
>  		i915_gem_object_set_cache_coherency(obj, I915_CACHE_NONE);
>  
>  	vma = i915_vma_instance(obj, &gt->ggtt->vm, NULL);
> -- 
> 2.25.1
> 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation