[Mesa-dev] [PATCH] radeonsi/gfx9: add a temporary workaround for a tessellation driver bug

[Nicolai Hähnle]

On 18.08.2017 19:06, Marek Olšák wrote:
> Ping.
> 
> On Wed, Aug 16, 2017 at 12:57 AM, Marek Olšák <maraeo at gmail.com> wrote:
>> From: Marek Olšák <marek.olsak at amd.com>
>>
>> The workaround will do for now. The root cause is still unknown.
>>
>> This fixes new piglit: 16in-1out

I don't see this test. Did you already send it out?


>> Cc: 17.1 17.2 <mesa-stable at lists.freedesktop.org>

Reviewed-by: Nicolai Hähnle <nicolai.haehnle at amd.com>


>> ---
>>   src/gallium/drivers/radeonsi/si_state_draw.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/gallium/drivers/radeonsi/si_state_draw.c b/src/gallium/drivers/radeonsi/si_state_draw.c
>> index f17f570..a26e38d 100644
>> --- a/src/gallium/drivers/radeonsi/si_state_draw.c
>> +++ b/src/gallium/drivers/radeonsi/si_state_draw.c
>> @@ -187,21 +187,25 @@ static void si_emit_derived_tess_state(struct si_context *sctx,
>>          /* Make sure the output data fits in the offchip buffer */
>>          *num_patches = MIN2(*num_patches,
>>                              (sctx->screen->tess_offchip_block_dw_size * 4) /
>>                              output_patch_size);
>>
>>          /* Not necessary for correctness, but improves performance. The
>>           * specific value is taken from the proprietary driver.
>>           */
>>          *num_patches = MIN2(*num_patches, 40);
>>
>> -       if (sctx->b.chip_class == SI) {
>> +       if (sctx->b.chip_class == SI ||
>> +           /* TODO: fix GFX9 where a threadgroup contains more than 1 wave and
>> +            * LS vertices per patch > HS vertices per patch. Piglit: 16in-1out */
>> +           (sctx->b.chip_class == GFX9 &&
>> +            num_tcs_input_cp > num_tcs_output_cp)) {
>>                  /* SI bug workaround, related to power management. Limit LS-HS
>>                   * threadgroups to only one wave.
>>                   */
>>                  unsigned one_wave = 64 / MAX2(num_tcs_input_cp, num_tcs_output_cp);
>>                  *num_patches = MIN2(*num_patches, one_wave);
>>          }
>>
>>          /* The VGT HS block increments the patch ID unconditionally
>>           * within a single threadgroup. This results in incorrect
>>           * patch IDs when instanced draws are used.
>> --
>> 2.7.4
>>
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