drm/amdgpu: Fix SDMA TO after GPU reset v3

After GPU reset amdgpu_vm_clear_bo triggers VM flush
but job->vm_pd_addr is not set causing SDMA TO.

v2:
Per advise by Christian König avoid flushing VM for jobs where
job->vm_pd_addr wasn't explicitly set.

v3:
Shortcut vm_flush_needed early.

Fixes cbd52851 drm/amdgpu: move setting the GART addr into TTM.
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -73,6 +73,7 @@ int amdgpu_job_alloc(struct amdgpu_device *adev, unsigned num_ibs,
 	amdgpu_sync_create(&(*job)->sync);
 	amdgpu_sync_create(&(*job)->sched_sync);
 	(*job)->vram_lost_counter = atomic_read(&adev->vram_lost_counter);
+	(*job)->vm_pd_addr = AMDGPU_BO_INVALID_OFFSET;
 
 	return 0;
 }

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

@@ -870,7 +870,8 @@ int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job, bool need_
 	}
 
 	gds_switch_needed &= !!ring->funcs->emit_gds_switch;
-	vm_flush_needed &= !!ring->funcs->emit_vm_flush;
+	vm_flush_needed &= !!ring->funcs->emit_vm_flush  &&
+			job->vm_pd_addr != AMDGPU_BO_INVALID_OFFSET;
 	pasid_mapping_needed &= adev->gmc.gmc_funcs->emit_pasid_mapping &&
 		ring->funcs->emit_wreg;