drm/amdgpu: suspend gfx userqueues

This patch adds suspend support for gfx userqueues. It typically does
the following:
- adds an enable_signaling function for the eviction fence, so that it
  can trigger the userqueue suspend,
- adds a delayed work to handle suspending of the eviction_fence
- adds a suspend function to handle suspending of userqueues which
  suspends all the queues under this userq manager and signals the
  eviction fence,
- adds a function to replace the old eviction fence with a new one and
  attach it to each of the objects,
- adds reference of userq manager in the eviction fence container so
  that it can be used in the suspend function.

V2: Addressed Christian's review comments:
    - schedule suspend work immediately

V4: Addressed Christian's review comments:
    - wait for pending uq fences before starting suspend, added
      queue->last_fence for the same
    - accommodate ev_fence_mgr into existing code
    - some bug fixes and NULL checks

V5: Addressed Christian's review comments (gitlab)
    - Wait for eviction fence to get signaled in destroy,
      don't signal it
    - Wait for eviction fence to get signaled in replace fence,
      don't signal it

V6: Addressed Christian's review comments
    - Do not destroy the old eviction fence until we have it replaced
    - Change the sequence of fence replacement sub-tasks
    - reusing the ev_fence delayed work for userqueue suspend as well
      (Shashank).

V7: Addressed Christian's review comments
    - give evf_mgr as argument (instead of fpriv) to replace_fence()
    - save ptr to evf_mgr in ev_fence (instead of uq_mgr)
    - modify suspend_all_queues logic to reflect error properly
    - remove the garbage drm_exec_lock section in wait_for_signal
    - grab the userqueue mutex before starting the wait for fence
    - remove the unrelated gobj check from signal_ioctl

V8: Added race condition fixes

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian Koenig <christian.koenig@amd.com>
Acked-by: Christian Koenig <christian.koenig@amd.com>
Signed-off-by: Shashank Sharma <shashank.sharma@amd.com>
Signed-off-by: Arvind Yadav <arvind.yadav@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -466,6 +466,16 @@ int amdgpu_userq_signal_ioctl(struct drm_device *dev, void *data,
 		}
 	}
 
+	/* Save the fence to wait for during suspend */
+	mutex_lock(&userq_mgr->userq_mutex);
+
+	/* Retrieve the user queue */
+	queue = idr_find(&userq_mgr->userq_idr, args->queue_id);
+	if (!queue) {
+		r = -ENOENT;
+		mutex_unlock(&userq_mgr->userq_mutex);
+	}
+
 	drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT,
 		      (num_read_bo_handles + num_write_bo_handles));
 
@@ -473,30 +483,35 @@ int amdgpu_userq_signal_ioctl(struct drm_device *dev, void *data,
 	drm_exec_until_all_locked(&exec) {
 		r = drm_exec_prepare_array(&exec, gobj_read, num_read_bo_handles, 1);
 		drm_exec_retry_on_contention(&exec);
-		if (r)
+		if (r) {
+			mutex_unlock(&userq_mgr->userq_mutex);
 			goto exec_fini;
+		}
 
 		r = drm_exec_prepare_array(&exec, gobj_write, num_write_bo_handles, 1);
 		drm_exec_retry_on_contention(&exec);
-		if (r)
+		if (r) {
+			mutex_unlock(&userq_mgr->userq_mutex);
 			goto exec_fini;
-	}
-
-	/*Retrieve the user queue */
-	queue = idr_find(&userq_mgr->userq_idr, args->queue_id);
-	if (!queue) {
-		r = -ENOENT;
-		goto exec_fini;
+		}
 	}
 
 	r = amdgpu_userq_fence_read_wptr(queue, &wptr);
-	if (r)
+	if (r) {
+		mutex_unlock(&userq_mgr->userq_mutex);
 		goto exec_fini;
+	}
 
 	/* Create a new fence */
 	r = amdgpu_userq_fence_create(queue, wptr, &fence);
-	if (r)
+	if (r) {
+		mutex_unlock(&userq_mgr->userq_mutex);
 		goto exec_fini;
+	}
+
+	dma_fence_put(queue->last_fence);
+	queue->last_fence = dma_fence_get(fence);
+	mutex_unlock(&userq_mgr->userq_mutex);
 
 	for (i = 0; i < num_read_bo_handles; i++) {
 		if (!gobj_read || !gobj_read[i]->resv)