drm/amdgpu/vcn: fix race condition issue for vcn start

Fix race condition issue when multiple vcn starts are called.

v2: Removed checking the return value of cancel_delayed_work_sync()
to prevent possible races here.

v3: Add total_submission_cnt to avoid gate power unexpectedly.

v4: Remove extra counter check, and reduce counter before idle
work schedule
Signed-off-by: James Zhu <James.Zhu@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_vcn.c

@@ -63,6 +63,8 @@ int amdgpu_vcn_sw_init(struct amdgpu_device *adev)
 	int i, r;
 
 	INIT_DELAYED_WORK(&adev->vcn.idle_work, amdgpu_vcn_idle_work_handler);
+	mutex_init(&adev->vcn.vcn_pg_lock);
+	atomic_set(&adev->vcn.total_submission_cnt, 0);
 
 	switch (adev->asic_type) {
 	case CHIP_RAVEN:
@@ -210,6 +212,7 @@ int amdgpu_vcn_sw_fini(struct amdgpu_device *adev)
 	}
 
 	release_firmware(adev->vcn.fw);
+	mutex_destroy(&adev->vcn.vcn_pg_lock);
 
 	return 0;
 }
@@ -307,7 +310,7 @@ static void amdgpu_vcn_idle_work_handler(struct work_struct *work)
 		fences += fence[j];
 	}
 
-	if (fences == 0) {
+	if (!fences && !atomic_read(&adev->vcn.total_submission_cnt)) {
 		amdgpu_gfx_off_ctrl(adev, true);
 		amdgpu_device_ip_set_powergating_state(adev, AMD_IP_BLOCK_TYPE_VCN,
 		       AMD_PG_STATE_GATE);
@@ -319,13 +322,14 @@ static void amdgpu_vcn_idle_work_handler(struct work_struct *work)
 void amdgpu_vcn_ring_begin_use(struct amdgpu_ring *ring)
 {
 	struct amdgpu_device *adev = ring->adev;
-	bool set_clocks = !cancel_delayed_work_sync(&adev->vcn.idle_work);
 
-	if (set_clocks) {
+	atomic_inc(&adev->vcn.total_submission_cnt);
+	cancel_delayed_work_sync(&adev->vcn.idle_work);
+
+	mutex_lock(&adev->vcn.vcn_pg_lock);
 	amdgpu_gfx_off_ctrl(adev, false);
 	amdgpu_device_ip_set_powergating_state(adev, AMD_IP_BLOCK_TYPE_VCN,
 	       AMD_PG_STATE_UNGATE);
-	}
 
 	if (adev->pg_flags & AMD_PG_SUPPORT_VCN_DPG)	{
 		struct dpg_pause_state new_state;
@@ -345,10 +349,13 @@ void amdgpu_vcn_ring_begin_use(struct amdgpu_ring *ring)
 
 		adev->vcn.pause_dpg_mode(adev, ring->me, &new_state);
 	}
+	mutex_unlock(&adev->vcn.vcn_pg_lock);
 }
 
 void amdgpu_vcn_ring_end_use(struct amdgpu_ring *ring)
 {
+	atomic_dec(&ring->adev->vcn.total_submission_cnt);
+
 	schedule_delayed_work(&ring->adev->vcn.idle_work, VCN_IDLE_TIMEOUT);
 }
 

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

@@ -200,6 +200,8 @@ struct amdgpu_vcn {
 	struct drm_gpu_scheduler *vcn_dec_sched[AMDGPU_MAX_VCN_INSTANCES];
 	uint32_t		 num_vcn_enc_sched;
 	uint32_t		 num_vcn_dec_sched;
+	struct mutex		 vcn_pg_lock;
+	atomic_t		 total_submission_cnt;
 
 	unsigned	harvest_config;
 	int (*pause_dpg_mode)(struct amdgpu_device *adev,