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

[Christian König]

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.

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;
>   	}