[Intel-gfx] [PATCH 3/4] drm/i915: Do not allocate unused PPAT entries

[Chris Wilson]

Quoting Zhi Wang (2017-09-05 20:58:26)
>  static void gen6_gmch_remove(struct i915_address_space *vm)
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
> index e10ca89..575da15 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.h
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
> @@ -131,6 +131,13 @@ typedef u64 gen8_ppgtt_pml4e_t;
>  #define PPAT_CACHED_INDEX              _PAGE_PAT /* WB LLCeLLC */
>  #define PPAT_DISPLAY_ELLC_INDEX                _PAGE_PCD /* WT eLLC */
>  
> +/* PPAT index = 4 * PAT + 2 * PCD + PWT */
> +static inline unsigned int ppat_bits_to_index(unsigned int bits)
> +{
> +       return (4 * !!(bits & _PAGE_PAT) + 2 * !!(bits & _PAGE_PCD)
> +               + !!(bits & _PAGE_PWT));
> +}

Let's not let this leak out of the gtt.c.

__alloc_ppat_entry(ppat, ppat_bits_to_index(PPAT_CACHED_PDE_INDEX), CHV_PPAT_SNOOP);

is horrible. bits_to_index() on an index is nonsense. We have a severe
naming issue here...
-Chris