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On 07/18/2011 12:55 AM, Chad Versace wrote:
> 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);
Eh... it seems like this will break compatibility with older versions of
Mesa. I haven't dug around, but there used to be a hack in DRI2 where a
client would request a depth buffer and a stencil buffer, but it would
get the same packed depth-stencil buffer for both. I guess that might
all be up in the DRI2 layer and not in the driver...
> @@ -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.
Mangled whitespace? Probably mixed tabs and spaces...
> */
> if (attachment == DRI2BufferStencil) {
> - pixmap_height /= 2;
> + pixmap_width = ALIGN(pixmap_width, 64);
> + pixmap_height = ALIGN(pixmap_height / 2, 64);
> pixmap_cpp *= 2;
> }
>
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