[PATCH] drm/amdgpu/vcn: fix video profile race condition (v2)

[Alex Deucher]

On Tue, Aug 12, 2025 at 7:08 PM David Wu <davidwu2 at amd.com> wrote:
>
> Hi Alex,
>
> still have a concern - the fence or submission_cnt could increase in
> begin_use but idle handler
> has finished counting it (as 0) so it could also power off vcn.

Ok, I think that is possible.  Will send an updated patch to handle
that case as well.

Alex

>
> David
>
> On 2025-08-12 16:58, 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()
> >
> > 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 | 37 ++++++++++++-------------
> >   1 file changed, 17 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..fd127e9461c89 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 +442,17 @@ 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) {
> >                       r = amdgpu_dpm_switch_power_profile(adev, PP_SMC_POWER_PROFILE_VIDEO,
> >                                                           false);
> >                       if (r)
> > @@ -470,13 +475,6 @@ void amdgpu_vcn_ring_begin_use(struct amdgpu_ring *ring)
> >
> >       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);
> >       if (!adev->vcn.workload_profile_active) {
> >               r = amdgpu_dpm_switch_power_profile(adev, PP_SMC_POWER_PROFILE_VIDEO,
> > @@ -487,7 +485,6 @@ 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);
> >