[Mesa-dev] [PATCH] intel: Fix stencil buffer to be W tiled
Ian Romanick
idr at freedesktop.org
Mon Jul 18 15:34:06 PDT 2011
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
On 07/18/2011 02:24 PM, Chad Versace wrote:
> On 07/18/2011 02:02 PM, Ian Romanick wrote:
>> On 07/18/2011 01:54 PM, Chad Versace wrote:
>>> On 07/18/2011 11:49 AM, Ian Romanick wrote:
>>>> 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 fix touches the following portions of code:
>>>>> - In intel_allocate_renderbuffer_storage(), allocate the stencil
>>>>> buffer with I915_TILING_NONE.
>>>>> - In intel_verify_dri2_has_hiz(), verify that the stencil buffer is
>>>>> not tiled.
>>>>> - In the stencil buffer's span functions, the tile's layout must be
>>>>> decoded in software.
>>>>
>>>>> This commit mutually depends on the xf86-video-intel commit
>>>>> dri: Do not tile stencil buffer
>>>>> Author: Chad Versace <chad at chad-versace.us>
>>>>> Date: Mon Jul 18 00:38:00 2011 -0700
>>>>
>>>>> On Gen6 with separate stencil enabled, fixes the following Piglit tests:
>>>>> bugs/fdo23670-drawpix_stencil
>>>>> general/stencil-drawpixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX16-copypixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX16-drawpixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX16-readpixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX1-copypixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX1-drawpixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX1-readpixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX4-copypixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX4-drawpixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX4-readpixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX8-copypixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX8-drawpixels
>>>>> spec/EXT_framebuffer_object/fbo-stencil-GL_STENCIL_INDEX8-readpixels
>>>>> spec/EXT_packed_depth_stencil/fbo-stencil-GL_DEPTH24_STENCIL8-copypixels
>>>>> spec/EXT_packed_depth_stencil/fbo-stencil-GL_DEPTH24_STENCIL8-readpixels
>>>>> spec/EXT_packed_depth_stencil/readpixels-24_8
>>>>
>>>>> Note: This is a candidate for the 7.11 branch.
>>>>
>>>>> CC: Eric Anholt <eric at anholt.net>
>>>>> CC: Kenneth Graunke <kenneth at whitecape.org>
>>>>> Signed-off-by: Chad Versace <chad at chad-versace.us>
>>>>> ---
>>>>> src/mesa/drivers/dri/intel/intel_clear.c | 6 ++
>>>>> src/mesa/drivers/dri/intel/intel_context.c | 9 ++-
>>>>> src/mesa/drivers/dri/intel/intel_fbo.c | 13 +++--
>>>>> src/mesa/drivers/dri/intel/intel_screen.h | 9 ++-
>>>>> src/mesa/drivers/dri/intel/intel_span.c | 85 ++++++++++++++++++++--------
>>>>> 5 files changed, 89 insertions(+), 33 deletions(-)
>>>>
>>>>> diff --git a/src/mesa/drivers/dri/intel/intel_clear.c b/src/mesa/drivers/dri/intel/intel_clear.c
>>>>> index dfca03c..5ab9873 100644
>>>>> --- a/src/mesa/drivers/dri/intel/intel_clear.c
>>>>> +++ b/src/mesa/drivers/dri/intel/intel_clear.c
>>>>> @@ -143,6 +143,12 @@ intelClear(struct gl_context *ctx, GLbitfield mask)
>>>>> */
>>>>> tri_mask |= BUFFER_BIT_STENCIL;
>>>>> }
>>>>> + else if (intel->has_separate_stencil &&
>>>>> + stencilRegion->tiling == I915_TILING_NONE) {
>>>>> + /* The stencil buffer is actually W tiled, which the hardware
>>>>> + * cannot blit to. */
>>>>> + tri_mask |= BUFFER_BIT_STENCIL;
>>>>> + }
>>>>> else {
>>>>> /* clearing all stencil bits, use blitting */
>>>>> blit_mask |= BUFFER_BIT_STENCIL;
>>>>> diff --git a/src/mesa/drivers/dri/intel/intel_context.c b/src/mesa/drivers/dri/intel/intel_context.c
>>>>> index 2ba1363..fe8be08 100644
>>>>> --- a/src/mesa/drivers/dri/intel/intel_context.c
>>>>> +++ b/src/mesa/drivers/dri/intel/intel_context.c
>>>>> @@ -1439,7 +1439,12 @@ intel_verify_dri2_has_hiz(struct intel_context *intel,
>>>>> assert(stencil_rb->Base.Format == MESA_FORMAT_S8);
>>>>> assert(depth_rb && depth_rb->Base.Format == MESA_FORMAT_X8_Z24);
>>>>
>>>>> - if (stencil_rb->region->tiling == I915_TILING_Y) {
>>>>> + if (stencil_rb->region->tiling == I915_TILING_NONE) {
>>>>> + /*
>>>>> + * The stencil buffer is actually W tiled. The region's tiling is
>>>>> + * I915_TILING_NONE, however, because the GTT is incapable of W
>>>>> + * fencing.
>>>>> + */
>>>>> intel->intelScreen->dri2_has_hiz = INTEL_DRI2_HAS_HIZ_TRUE;
>>>>> return;
>>>>> } else {
>>>>> @@ -1527,7 +1532,7 @@ intel_verify_dri2_has_hiz(struct intel_context *intel,
>>>>> * Presently, however, no verification or clean up is necessary, and
>>>>> * execution should not reach here. If the framebuffer still has a hiz
>>>>> * region, then we have already set dri2_has_hiz to true after
>>>>> - * confirming above that the stencil buffer is Y tiled.
>>>>> + * confirming above that the stencil buffer is W tiled.
>>>>> */
>>>>> assert(0);
>>>>> }
>>>>> diff --git a/src/mesa/drivers/dri/intel/intel_fbo.c b/src/mesa/drivers/dri/intel/intel_fbo.c
>>>>> index 1669af2..507cc33 100644
>>>>> --- a/src/mesa/drivers/dri/intel/intel_fbo.c
>>>>> +++ b/src/mesa/drivers/dri/intel/intel_fbo.c
>>>>> @@ -173,6 +173,9 @@ intel_alloc_renderbuffer_storage(struct gl_context * ctx, struct gl_renderbuffer
>>>>
>>>>> if (irb->Base.Format == MESA_FORMAT_S8) {
>>>>> /*
>>>>> + * The stencil buffer is W tiled. However, we request from the kernel a
>>>>> + * non-tiled buffer because the GTT is incapable of W fencing.
>>>>> + *
>>>>> * The stencil buffer has quirky pitch requirements. From Vol 2a,
>>>>> * 11.5.6.2.1 3DSTATE_STENCIL_BUFFER, field "Surface Pitch":
>>>>> * The pitch must be set to 2x the value computed based on width, as
>>>>> @@ -180,14 +183,14 @@ intel_alloc_renderbuffer_storage(struct gl_context * ctx, struct gl_renderbuffer
>>>>> * 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.
>>>>> */
>>>>> irb->region = intel_region_alloc(intel->intelScreen,
>>>>> - I915_TILING_Y,
>>>>> + I915_TILING_NONE,
>>>>> cpp * 2,
>>>>> - width,
>>>>> - height / 2,
>>>>> + ALIGN(width, 64),
>>>>> + /* XXX: Maybe align to 128? */
>>>>> + ALIGN(height / 2, 64),
>>>>> GL_TRUE);
>>>>> if (!irb->region)
>>>>> return false;
>>>>> diff --git a/src/mesa/drivers/dri/intel/intel_screen.h b/src/mesa/drivers/dri/intel/intel_screen.h
>>>>> index b2013af..9dd6a52 100644
>>>>> --- a/src/mesa/drivers/dri/intel/intel_screen.h
>>>>> +++ b/src/mesa/drivers/dri/intel/intel_screen.h
>>>>> @@ -63,9 +63,12 @@
>>>>> * x8_z24 and s8).
>>>>> *
>>>>> * Eventually, intel_update_renderbuffers() makes a DRI2 request for
>>>>> - * DRI2BufferStencil and DRI2BufferHiz. If the returned buffers are Y tiled,
>>>>> - * then we joyfully set intel_screen.dri2_has_hiz to true and continue as if
>>>>> - * nothing happend.
>>>>> + * DRI2BufferStencil and DRI2BufferHiz. If the stencil buffer's tiling is
>>>>> + * I915_TILING_NONE [1], then we joyfully set intel_screen.dri2_has_hiz to
>>>>> + * true and continue as if nothing happend.
>>>>> + *
>>>>> + * [1] The stencil buffer is actually W tiled. However, we request from the
>>>>> + * kernel a non-tiled buffer because the GTT is incapable of W fencing.
>>>>> *
>>>>> * If the buffers are X tiled, however, the handshake has failed and we must
>>>>> * clean up.
>>>>> diff --git a/src/mesa/drivers/dri/intel/intel_span.c b/src/mesa/drivers/dri/intel/intel_span.c
>>>>> index 153803f..d306432 100644
>>>>> --- a/src/mesa/drivers/dri/intel/intel_span.c
>>>>> +++ b/src/mesa/drivers/dri/intel/intel_span.c
>>>>> @@ -131,38 +131,77 @@ intel_set_span_functions(struct intel_context *intel,
>>>>> int miny = 0; \
>>>>> int maxx = rb->Width; \
>>>>> int maxy = rb->Height; \
>>>>> - int stride = rb->RowStride; \
>>>>> - uint8_t *buf = rb->Data; \
>>>>> + \
>>>>> + /* \
>>>>> + * Here we ignore rb->Data and rb->RowStride as set by \
>>>>> + * intelSpanRenderStart. Since intel_offset_S8 decodes the W tile \
>>>>> + * manually, the region's *real* base address and stride is \
>>>>> + * required. \
>>>>> + */ \
>>>>> + struct intel_renderbuffer *irb = intel_renderbuffer(rb); \
>>>>> + uint8_t *buf = irb->region->buffer->virtual; \
>>>>> + unsigned stride = irb->region->pitch; \
>>>>> + unsigned height = 2 * irb->region->height; \
>>>>> + bool flip = rb->Name == 0; \
>>>>
>>>>> -/* Don't flip y. */
>>>>> #undef Y_FLIP
>>>>> -#define Y_FLIP(y) y
>>>>> +#define Y_FLIP(y) ((1 - flip) * y + flip * (height - 1 - y))
>>>>
>>>>> /**
>>>>> * \brief Get pointer offset into stencil buffer.
>>>>> *
>>>>> - * The stencil buffer interleaves two rows into one. Yay for crazy hardware.
>>>>> - * The table below demonstrates how the pointer arithmetic behaves for a buffer
>>>>> - * with positive stride (s=stride).
>>>>> - *
>>>>> - * x | y | byte offset
>>>>> - * --------------------------
>>>>> - * 0 | 0 | 0
>>>>> - * 0 | 1 | 1
>>>>> - * 1 | 0 | 2
>>>>> - * 1 | 1 | 3
>>>>> - * ... | ... | ...
>>>>> - * 0 | 2 | s
>>>>> - * 0 | 3 | s + 1
>>>>> - * 1 | 2 | s + 2
>>>>> - * 1 | 3 | s + 3
>>>>> - *
>>>>> + * The stencil buffer is W tiled. Since the GTT is incapable of W fencing, we
>>>>> + * must decode the tile's layout in software.
>>>>> *
>>>>> + * See
>>>>> + * - PRM, 2011 Sandy Bridge, Volume 1, Part 2, Section 4.5.2.1 W-Major Tile
>>>>> + * Format.
>>>>> + * - PRM, 2011 Sandy Bridge, Volume 1, Part 2, Section 4.5.3 Tiling Algorithm
>>>>> */
>>>>> -static inline intptr_t
>>>>> -intel_offset_S8(int stride, GLint x, GLint y)
>>>>> +static inline uintptr_t
>>>>
>>>> Why the type change?
>>
>>> Two reasons.
>>
>>> 1. I redeclared the parameters as unsigned so to generate better code.
>>> Since x, y, and stride are unsigned, the division and modulo operators
>>> generate shift and bit-logic instructions rather than the slower arithmetic
>>> instructions.
>>
>> Is stride always unsigned now?
>
> intelSpanRenderStart still sets rb->RowStride to be negative for system
> stencil buffers. But we ignore that and use a positive stride instead.
> To quote the hunk above:
>
> + /* \
> + * Here we ignore rb->Data and rb->RowStride as set by \
> + * intelSpanRenderStart. Since intel_offset_S8 decodes the W tile \
> + * manually, the region's *real* base address and stride is \
> + * required. \
> + */ \
> + struct intel_renderbuffer *irb = intel_renderbuffer(rb); \
> + uint8_t *buf = irb->region->buffer->virtual; \
> + unsigned stride = irb->region->pitch;
>
> By setting the buf and stride to the *real* base address and stride,
> intel_offset_S8 can implement the exact W-tiling algorithm as described
> in the bspec. (PRM, 2011 Sandy Bridge, Volume 1, Part 2, Section 4.5.3 Tiling
> Algorithm).
>
> If intel_offset_S8 instead used rb->Data and rb->RowStride as the buffer's
> base address and stride, then intel_offset_S8 would essentially
> need two implementations, like this:
> intptr_t
> intel_offset_S8(...)
> {
> if (stride > 0) {
> // do normal stuff;
> } else {
> // do upside down stuff;
> }
> }
>
> I'd like to avoid such a bifurcated function.
That makes perfect sense. Thanks for clearing that all up.
>> Will it always be in the future?
>
> Yes.
>
>> This is the problem that we encountered with bug #37351 (fixed by e8b1c6d).
>
> Ah... Thanks for recalling that bug. I believe setting the return type of
> intel_offset_S8 to be intptr_t will eliminate reoccurrence of this bug. Do you agree?
It should.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.11 (GNU/Linux)
Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/
iEYEARECAAYFAk4ktN4ACgkQX1gOwKyEAw/fxQCeMr45By87f0YxBNU+Fp62C1LV
asMAnitL5MjvaIKXgXUIGFDof8hNHRPL
=5kb4
-----END PGP SIGNATURE-----
More information about the mesa-dev
mailing list