[PATCH] drm/amdgpu/vcn: fix video profile race condition (v3)
Alex Deucher
alexdeucher at gmail.com
Wed Aug 13 16:51:11 UTC 2025
On Wed, Aug 13, 2025 at 12:39 PM Wu, David <davidwu2 at amd.com> wrote:
>
> Hi Alex,
>
> The addition of total_submission_cnt should work - in that
> it is unlikely to have a context switch right after the begin_use().
> The suggestion of moving it inside the lock (which I prefer in case someone
> adds more before the lock and not reviewed thoroughly)
> - up to you to decide.
>
> Reviewed-by: David (Ming Qiang) Wu <David.Wu3 at amd.com>
>
> Thanks,
> David
> On 8/13/2025 9:45 AM, Alex Deucher wrote:
> > If there are multiple instances of the VCN running,
> > we may end up switching the video profile while another
> > instance is active because we only take into account
> > the current instance's submissions. Look at all
> > outstanding fences for the video profile.
> >
> > v2: drop early exit in begin_use()
> > v3: handle possible race between begin_use() work handler
> >
> > Fixes: 3b669df92c85 ("drm/amdgpu/vcn: adjust workload profile handling")
> > Reviewed-by: Sathishkumar S <sathishkumar.sundararaju at amd.com> (v1)
> > Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> > ---
> > drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c | 40 ++++++++++++-------------
> > drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h | 1 +
> > 2 files changed, 21 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
> > index 9a76e11d1c184..593c1ddf8819b 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
> > @@ -415,19 +415,25 @@ static void amdgpu_vcn_idle_work_handler(struct work_struct *work)
> > struct amdgpu_vcn_inst *vcn_inst =
> > container_of(work, struct amdgpu_vcn_inst, idle_work.work);
> > struct amdgpu_device *adev = vcn_inst->adev;
> > - unsigned int fences = 0, fence[AMDGPU_MAX_VCN_INSTANCES] = {0};
> > - unsigned int i = vcn_inst->inst, j;
> > + unsigned int total_fences = 0, fence[AMDGPU_MAX_VCN_INSTANCES] = {0};
> > + unsigned int i, j;
> > int r = 0;
> >
> > - if (adev->vcn.harvest_config & (1 << i))
> > + if (adev->vcn.harvest_config & (1 << vcn_inst->inst))
> > return;
> >
> > - for (j = 0; j < adev->vcn.inst[i].num_enc_rings; ++j)
> > - fence[i] += amdgpu_fence_count_emitted(&vcn_inst->ring_enc[j]);
> > + for (i = 0; i < adev->vcn.num_vcn_inst; ++i) {
> > + struct amdgpu_vcn_inst *v = &adev->vcn.inst[i];
> > +
> > + for (j = 0; j < v->num_enc_rings; ++j)
> > + fence[i] += amdgpu_fence_count_emitted(&v->ring_enc[j]);
> > + fence[i] += amdgpu_fence_count_emitted(&v->ring_dec);
> > + total_fences += fence[i];
> > + }
> >
> > /* Only set DPG pause for VCN3 or below, VCN4 and above will be handled by FW */
> > if (adev->pg_flags & AMD_PG_SUPPORT_VCN_DPG &&
> > - !adev->vcn.inst[i].using_unified_queue) {
> > + !vcn_inst->using_unified_queue) {
> > struct dpg_pause_state new_state;
> >
> > if (fence[i] ||
> > @@ -436,18 +442,18 @@ static void amdgpu_vcn_idle_work_handler(struct work_struct *work)
> > else
> > new_state.fw_based = VCN_DPG_STATE__UNPAUSE;
> >
> > - adev->vcn.inst[i].pause_dpg_mode(vcn_inst, &new_state);
> > + vcn_inst->pause_dpg_mode(vcn_inst, &new_state);
> > }
> >
> > - fence[i] += amdgpu_fence_count_emitted(&vcn_inst->ring_dec);
> > - fences += fence[i];
> > -
> > - if (!fences && !atomic_read(&vcn_inst->total_submission_cnt)) {
> > + if (!fence[vcn_inst->inst] && !atomic_read(&vcn_inst->total_submission_cnt)) {
> > + /* This is specific to this instance */
> > mutex_lock(&vcn_inst->vcn_pg_lock);
> > vcn_inst->set_pg_state(vcn_inst, AMD_PG_STATE_GATE);
> > mutex_unlock(&vcn_inst->vcn_pg_lock);
> > mutex_lock(&adev->vcn.workload_profile_mutex);
> > - if (adev->vcn.workload_profile_active) {
> > + /* This is global and depends on all VCN instances */
> > + if (adev->vcn.workload_profile_active && !total_fences &&
> > + !atomic_read(&adev->vcn.total_submission_cnt)) {
> > r = amdgpu_dpm_switch_power_profile(adev, PP_SMC_POWER_PROFILE_VIDEO,
> > false);
> > if (r)
> > @@ -467,16 +473,10 @@ void amdgpu_vcn_ring_begin_use(struct amdgpu_ring *ring)
> > int r = 0;
> >
> > atomic_inc(&vcn_inst->total_submission_cnt);
> > + atomic_inc(&adev->vcn.total_submission_cnt);
> move this addition down inside the mutex lock
> > cancel_delayed_work_sync(&vcn_inst->idle_work);
> >
> > - /* We can safely return early here because we've cancelled the
> > - * the delayed work so there is no one else to set it to false
> > - * and we don't care if someone else sets it to true.
> > - */
> > - if (adev->vcn.workload_profile_active)
> > - goto pg_lock;
> > -
> > mutex_lock(&adev->vcn.workload_profile_mutex);
> move to here:
> atomic_inc(&adev->vcn.total_submission_cnt);
> I think this should work for multiple instances.
Why does this need to be protected by the mutex?
Alex
>
> David
> > if (!adev->vcn.workload_profile_active) {
> > r = amdgpu_dpm_switch_power_profile(adev, PP_SMC_POWER_PROFILE_VIDEO,
> > @@ -487,7 +487,6 @@ void amdgpu_vcn_ring_begin_use(struct amdgpu_ring *ring)
> > }
> > mutex_unlock(&adev->vcn.workload_profile_mutex);
> >
> > -pg_lock:
> > mutex_lock(&vcn_inst->vcn_pg_lock);
> > vcn_inst->set_pg_state(vcn_inst, AMD_PG_STATE_UNGATE);
> >
> > @@ -528,6 +527,7 @@ void amdgpu_vcn_ring_end_use(struct amdgpu_ring *ring)
> > atomic_dec(&ring->adev->vcn.inst[ring->me].dpg_enc_submission_cnt);
> >
> > atomic_dec(&ring->adev->vcn.inst[ring->me].total_submission_cnt);
> > + atomic_dec(&ring->adev->vcn.total_submission_cnt);
> >
> > schedule_delayed_work(&ring->adev->vcn.inst[ring->me].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 b3fb1d0e43fc9..febc3ce8641ff 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.h
> > @@ -352,6 +352,7 @@ struct amdgpu_vcn {
> >
> > uint16_t inst_mask;
> > uint8_t num_inst_per_aid;
> > + atomic_t total_submission_cnt;
> >
> > /* IP reg dump */
> > uint32_t *ip_dump;
>
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