drm/amdgpu: cache the fence to wait for a VMID

Beneficial when a lot of processes are waiting for VMIDs.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c

@@ -205,6 +205,9 @@ static int amdgpu_vmid_grab_idle(struct amdgpu_vm *vm,
 	unsigned i;
 	int r;
 
+	if (ring->vmid_wait && !dma_fence_is_signaled(ring->vmid_wait))
+		return amdgpu_sync_fence(adev, sync, ring->vmid_wait, false);
+
 	fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_KERNEL);
 	if (!fences)
 		return -ENOMEM;
@@ -239,9 +242,9 @@ static int amdgpu_vmid_grab_idle(struct amdgpu_vm *vm,
 		}
 
 		r = amdgpu_sync_fence(adev, sync, &array->base, false);
-		dma_fence_put(&array->base);
+		dma_fence_put(ring->vmid_wait);
+		ring->vmid_wait = &array->base;
 		return r;
-
 	}
 	kfree(fences);
 

drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c

@@ -360,6 +360,9 @@ void amdgpu_ring_fini(struct amdgpu_ring *ring)
 
 	amdgpu_debugfs_ring_fini(ring);
 
+	dma_fence_put(ring->vmid_wait);
+	ring->vmid_wait = NULL;
+
 	ring->adev->rings[ring->idx] = NULL;
 }
 

drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h

@@ -196,6 +196,7 @@ struct amdgpu_ring {
 	u64			cond_exe_gpu_addr;
 	volatile u32		*cond_exe_cpu_addr;
 	unsigned		vm_inv_eng;
+	struct dma_fence	*vmid_wait;
 	bool			has_compute_vm_bug;
 
 	atomic_t		num_jobs[DRM_SCHED_PRIORITY_MAX];