[PATCH] drm/amdgpu: do not execute 0-sized IBs

[Pelloux-prayer, Pierre-eric]

On 03/10/2019 10:09, Christian König wrote:
> Am 03.10.19 um 10:03 schrieb Pelloux-prayer, Pierre-eric:
>> This can be safely skipped entirely.
>> This seems to help with https://bugs.freedesktop.org/show_bug.cgi?id=111481.
> 
> NAK, please instead fix gmc_v10_0_flush_gpu_tlb to include at least some NOP in the submitted IBs.

Is there any interest in executing an empty (or only filled with NOPs) IB?

Anyway I can modify the patch to do this.

Thanks,
Pierre-Eric

> 
> Christian.
> 
>>
>> Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
>> index 60655834d649..aa163e679f1f 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
>> @@ -227,6 +227,11 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned num_ibs,
>>               !amdgpu_sriov_vf(adev)) /* for SRIOV preemption, Preamble CE ib must be inserted anyway */
>>               continue;
>>   +        if (ib->length_dw == 0) {
>> +            /* On Navi gmc_v10_0_flush_gpu_tlb emits 0 sized IB */
>> +            continue;
>> +        }
>> +
>>           amdgpu_ring_emit_ib(ring, job, ib, status);
>>           status &= ~AMDGPU_HAVE_CTX_SWITCH;
>>       }
>