[PATCH v3 1/4] drm/amdgpu/vcn: fix race condition issue for vcn start

[James Zhu]

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.

Signed-off-by: James Zhu <James.Zhu at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c | 22 +++++++++++++++-------
 drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h |  2 ++
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
index a41272f..6aafda1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
+++ b/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 +310,8 @@ static void amdgpu_vcn_idle_work_handler(struct work_struct *work)
 		fences += fence[j];
 	}
 
-	if (fences == 0) {
+	if (fences == 0 &&
+		likely(atomic_read(&adev->vcn.total_submission_cnt) == 0)) {
 		amdgpu_gfx_off_ctrl(adev, true);
 		amdgpu_device_ip_set_powergating_state(adev, AMD_IP_BLOCK_TYPE_VCN,
 		       AMD_PG_STATE_GATE);
@@ -319,13 +323,14 @@ 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) {
-		amdgpu_gfx_off_ctrl(adev, false);
-		amdgpu_device_ip_set_powergating_state(adev, AMD_IP_BLOCK_TYPE_VCN,
-		       AMD_PG_STATE_UNGATE);
-	}
+	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;
@@ -345,11 +350,14 @@ 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)
 {
 	schedule_delayed_work(&ring->adev->vcn.idle_work, VCN_IDLE_TIMEOUT);
+	if (unlikely(atomic_dec_return(&ring->adev->vcn.total_submission_cnt) < 0))
+		atomic_set(&ring->adev->vcn.total_submission_cnt, 0);
 }
 
 int amdgpu_vcn_dec_ring_test_ring(struct amdgpu_ring *ring)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h
index 6fe0573..111c4cc 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h
+++ b/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,
-- 
2.7.4