Am Montag, den 18.07.2011, 00:55 -0700 schrieb Chad Versace:
> Until now, the stencil buffer was allocated as a Y tiled buffer, because
> in several locations the PRM states that it is. However, it is actually
> W tiled. From the PRM, 2011 Sandy Bridge, Volume 1, Part 2, Section
> 4.5.2.1 W-Major Format:
>     W-Major Tile Format is used for separate stencil.
> 
> The GTT is incapable of W fencing, so we allocate the stencil buffer with
> I915_TILING_NONE and decode the tile's layout in software.
> 
> This commit mutually depends on the mesa commit:
>     intel: Fix stencil buffer to be W tiled
>     Author: Chad Versace <c...@chad-versace.us>
>     Date:   Mon Jul 18 00:37:45 2011 -0700
> 
> CC: Eric Anholt <e...@anholt.net>
> CC: Kenneth Graunke <kenn...@whitecape.org>
> Signed-off-by: Chad Versace <c...@chad-versace.us>
> ---
>  src/intel_dri.c |   16 ++++++++++++----
>  1 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/src/intel_dri.c b/src/intel_dri.c
> index 5ea7c2c..4652dc7 100644
> --- a/src/intel_dri.c
> +++ b/src/intel_dri.c
> @@ -336,7 +336,6 @@ I830DRI2CreateBuffer(DrawablePtr drawable, unsigned int 
> attachment,
>                       switch (attachment) {
>                       case DRI2BufferDepth:
>                       case DRI2BufferDepthStencil:
> -                     case DRI2BufferStencil:
>                       case DRI2BufferHiz:
>                               if (SUPPORTS_YTILING(intel)) {
>                                       hint |= INTEL_CREATE_PIXMAP_TILING_Y;
> @@ -351,6 +350,14 @@ I830DRI2CreateBuffer(DrawablePtr drawable, unsigned int 
> attachment,
>                       case DRI2BufferFrontRight:
>                               hint |= INTEL_CREATE_PIXMAP_TILING_X;
>                               break;
> +                     case DRI2BufferStencil:
> +                             /*
> +                              * The stencil buffer is W tiled. However, we
> +                              * request from the kernel a non-tiled buffer
> +                              * because the GTT is incapable of W fencing.
> +                              */
> +                             hint |= INTEL_CREATE_PIXMAP_TILING_NONE;
> +                             break;
>                       default:
>                               free(privates);
>                               free(buffer);
> @@ -368,11 +375,12 @@ I830DRI2CreateBuffer(DrawablePtr drawable, unsigned int 
> attachment,
>                * To accomplish this, we resort to the nasty hack of doubling
>                * the drm region's cpp and halving its height.
>                *
> -              * If we neglect to double the pitch, then
> -              * drm_intel_gem_bo_map_gtt() maps the memory incorrectly.
> +              * If we neglect to double the pitch, then render corruption
> +                 * occurs.

The alignment does not seem to match.

>                */
>               if (attachment == DRI2BufferStencil) {
> -                     pixmap_height /= 2;
> +                     pixmap_width = ALIGN(pixmap_width, 64);
> +                     pixmap_height = ALIGN(pixmap_height / 2, 64);
>                       pixmap_cpp *= 2;
>               }


Thanks,

Paul

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