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

[Pelloux-prayer, Pierre-eric]

This can be safely skipped entirely.
This seems to help with https://bugs.freedesktop.org/show_bug.cgi?id=111481.

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;
 	}
-- 
2.23.0.rc1