Re: [PATCH v4 1/4] drm/amdgpu/vcn: fix race condition issue for vcn start

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Am 11.03.20 um 15:15 schrieb 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.

v4: Remove extra counter check, and reduce counter before idle
work schedule

Signed-off-by: James Zhu <James.Zhu@xxxxxxx>
---
  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..2fa2891 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)) {

The indentation here looks off, maybe just write that as !fences && !atomic_read(&adev->vcn.total_submission_cnt).

Apart from that looks good to me now,
Christian.

  		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;
@@ -345,10 +350,13 @@ 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);
  }
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,

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