[Mesa-dev] [PATCH v3 06/14] i965/miptree: Use BO_ALLOC_ZEROED for CCS_E buffers

[Jason Ekstrand]

Chad, you missed this one.

On Wed, Jul 12, 2017 at 9:23 PM, Jason Ekstrand <jason at jlekstrand.net>
wrote:

> ---
>  src/mesa/drivers/dri/i965/intel_mipmap_tree.c | 36
> ++++++++++-----------------
>  1 file changed, 13 insertions(+), 23 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> index fc7b48f..fea19a8 100644
> --- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> +++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> @@ -1837,13 +1837,20 @@ intel_miptree_alloc_ccs(struct brw_context *brw,
>     if (!aux_state)
>        return false;
>
> -   /* In case of compression mcs buffer needs to be initialised requiring
> the
> -    * buffer to be immediately mapped to cpu space for writing. Therefore
> do
> -    * not use the gpu access flag which can cause an unnecessary delay if
> the
> -    * backing pages happened to be just used by the GPU.
> +   /* When CCS_E is used, we need to ensure that the CCS starts off in a
> valid
> +    * state.  From the Sky Lake PRM, "MCS Buffer for Render Target(s)":
> +    *
> +    *    "If Software wants to enable Color Compression without Fast
> clear,
> +    *    Software needs to initialize MCS with zeros."
> +    *
> +    * A CCS value of 0 indicates that the corresponding block is in the
> +    * pass-through state which is what we want.
> +    *
> +    * For CCS_D, on the other hand, we don't care as we're about to
> perform a
> +    * fast-clear operation.  In that case, being hot in caches more
> useful.
>      */
> -   const uint32_t alloc_flags =
> -      mt->aux_usage == ISL_AUX_USAGE_CCS_E ? 0 : BO_ALLOC_FOR_RENDER;
> +   const uint32_t alloc_flags = mt->aux_usage == ISL_AUX_USAGE_CCS_E ?
> +                                BO_ALLOC_ZEROED : BO_ALLOC_FOR_RENDER;
>     mt->mcs_buf = intel_alloc_aux_buffer(brw, "ccs-miptree",
>                                          &temp_ccs_surf, alloc_flags, mt);
>     if (!mt->mcs_buf) {
> @@ -1853,23 +1860,6 @@ intel_miptree_alloc_ccs(struct brw_context *brw,
>
>     mt->aux_state = aux_state;
>
> -   /* From Gen9 onwards single-sampled (non-msrt) auxiliary buffers are
> -    * used for lossless compression which requires similar initialisation
> -    * as multi-sample compression.
> -    */
> -   if (mt->aux_usage == ISL_AUX_USAGE_CCS_E) {
> -      /* Hardware sets the auxiliary buffer to all zeroes when it does
> full
> -       * resolve. Initialize it accordingly in case the first renderer is
> -       * cpu (or other none compression aware party).
> -       *
> -       * This is also explicitly stated in the spec (MCS Buffer for Render
> -       * Target(s)):
> -       *   "If Software wants to enable Color Compression without Fast
> clear,
> -       *    Software needs to initialize MCS with zeros."
> -       */
> -      intel_miptree_init_mcs(brw, mt, 0);
> -   }
> -
>     return true;
>  }
>
> --
> 2.5.0.400.gff86faf
>
>
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