[Mesa-dev] [PATCH] r600: fix FMASK allocation on r600/700

[Alex Deucher]

On Wed, Dec 10, 2014 at 5:40 AM, Marek Olšák <maraeo at gmail.com> wrote:
> bpe is in bytes, not bits, so you're overallocating the size 8 times.
> No wonder it works.
>
> As far as I can see, FMASK allocation is the same on R600 and
> Evergreen. Since the allocator accepts bpe in bytes, I multiplied
> nr_samples with bpp and divided by 8.
>
> 2xMSAA:
> bpp = 2 bits
> nr_samples = log2(bpp) = 1
> final bpe = (2*1)/8 rounded up = 1
>
> 4xMSAA:
> bpp = 4 bits
> nr_samples = log2(bpp) = 2
> final bpe = (4*2)/8 = 1
>
> 8xMSAA:
> bpp = 8 bits
> nr_samples = log2(bpp) = 3
> final bpe = (8*3)/8 rounded up to next pow2 = 4
>
> So you can see the code was correct. It's the tiling or alignment that
> must have changed.

I haven't looked at the code recently, but are we aligning pitch to
groupsize (256 bytes)?

The pitch padding alignment must be multiplied times the number of 8x8
tiles required to exactly fill the GroupSize.  The pitch alignment is
increased by a factor of 16 for 2-sample and 4 for 4-sample or
8-sample.

Alex

>
> Marek
>
>
> On Wed, Dec 10, 2014 at 3:11 AM, Dave Airlie <airlied at gmail.com> wrote:
>> From: Dave Airlie <airlied at redhat.com>
>>
>> According to NDA docs:
>> FMASK surfaces are addressed identically a surface with num_samples bits per element, and
>> log2(num_samples) samples. For example, an FMASK for an 8-sample surface would be addressed
>> identically to a color surface with 8 bits per element and 3 samples.
>>
>> Separate the r600 fmask allocation out, and workaround
>> a bug in the libdrm surface allocation which blocks a 3
>> sample surface, just round it up to 4.
>>
>> This fixes hangs with ext_framebuffer_multisample-clip-and-scissor-blit 8 msaa
>> and destination clipping on my rv635.
>>
>> Signed-off-by: Dave Airlie <airlied at redhat.com>
>> ---
>>  src/gallium/drivers/radeon/r600_texture.c | 49 +++++++++++++++++++------------
>>  1 file changed, 30 insertions(+), 19 deletions(-)
>>
>> diff --git a/src/gallium/drivers/radeon/r600_texture.c b/src/gallium/drivers/radeon/r600_texture.c
>> index fdf4d76..3ca460a 100644
>> --- a/src/gallium/drivers/radeon/r600_texture.c
>> +++ b/src/gallium/drivers/radeon/r600_texture.c
>> @@ -299,27 +299,38 @@ void r600_texture_get_fmask_info(struct r600_common_screen *rscreen,
>>                 fmask.flags |= RADEON_SURF_HAS_TILE_MODE_INDEX;
>>         }
>>
>> -       switch (nr_samples) {
>> -       case 2:
>> -       case 4:
>> -               fmask.bpe = 1;
>> -               if (rscreen->chip_class <= CAYMAN) {
>> -                       fmask.bankh = 4;
>> +       if (rscreen->chip_class <= R700) {
>> +               /*
>> +                * R600/700 -
>> +                * FMASK surfaces are addressed identically a surface with num_samples
>> +                * bits per element, and log2(num_samples) samples.
>> +                */
>> +               if (nr_samples != 2 && nr_samples != 4 && nr_samples != 8) {
>> +                       R600_ERR("Invalid sample count for FMASK allocation.\n");
>> +                       return;
>>                 }
>> -               break;
>> -       case 8:
>> -               fmask.bpe = 4;
>> -               break;
>> -       default:
>> -               R600_ERR("Invalid sample count for FMASK allocation.\n");
>> -               return;
>> -       }
>> +               fmask.bpe = nr_samples;
>> +               fmask.nsamples = log2(nr_samples);
>> +               /* surface allocator won't do 3 samples */
>> +               if (fmask.nsamples == 3)
>> +                       fmask.nsamples = 4;
>>
>> -       /* Overallocate FMASK on R600-R700 to fix colorbuffer corruption.
>> -        * This can be fixed by writing a separate FMASK allocator specifically
>> -        * for R600-R700 asics. */
>> -       if (rscreen->chip_class <= R700) {
>> -               fmask.bpe *= 2;
>> +       } else {
>> +               switch (nr_samples) {
>> +               case 2:
>> +               case 4:
>> +                       fmask.bpe = 1;
>> +                       if (rscreen->chip_class <= CAYMAN) {
>> +                               fmask.bankh = 4;
>> +                       }
>> +                       break;
>> +               case 8:
>> +                       fmask.bpe = 4;
>> +                       break;
>> +               default:
>> +                       R600_ERR("Invalid sample count for FMASK allocation.\n");
>> +                       return;
>> +               }
>>         }
>>
>>         if (rscreen->ws->surface_init(rscreen->ws, &fmask)) {
>> --
>> 2.1.0
>>
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