On Wed, Aug 13, 2025 at 4:58 PM Sundararaju, Sathishkumar
<sathishkumar.sundarar...@amd.com> wrote:
>
>
> On 8/14/2025 1:35 AM, Alex Deucher wrote:
> > On Wed, Aug 13, 2025 at 2:23 PM Sundararaju, Sathishkumar
> > <sathishkumar.sundarar...@amd.com> wrote:
> >> Hi Alex, Hi David,
> >>
> >> I see David's concern but his suggestion yet wont solve the problem,
> >> neither the current form , reason :-
> >>
> >> The emitted fence count and total submission count are fast transients
> >> which frequently become 0 in between video decodes (between jobs) even
> >> with the atomics and locks there can be a switch of video power profile,
> >> in the current form of patch that window is minimized, but still can
> >> happen if stress tested. But power state of any instance becoming zero
> > Can you explain how this can happen? I'm not seeing it.
> Consider this situation, inst0 and inst1 actively decoding, inst0 decode
> completes, delayed idle work starts.
> inst0 idle handler can read 0 total fences and 0 total submission count,
> even if inst1 is actively decoding,
> that's between the jobs,
> - as begin_use increaments vcn.total_submission_cnt and end_use
> decreaments vcn.total_submission_cnt that can be 0.
> - if outstanding fences are cleared and no new emitted fence, between
> jobs , can be 0.
> - both of the above conditions do not mean video decode is complete on
> inst1, it is actively decoding.
How can there be active decoding without an outstanding fence? In
that case, total_fences (fences from both instances) would be non-0.
Alex
>
> Whereas if instances are powered off we are sure idle time is past and
> it is powered off, no possible way of
> active video decode, when all instances are off we can safely assume no
> active decode and global lock protects
> it against new begin_use on any instance. But the only distant concern
> is global common locks w.r.t perf, but we
> are already having a global workprofile mutex , so there shouldn't be
> any drop in perf, with just one single
> global lock for all instances.
>
> Just sending out a patch with this fix, will leave it to you to decide
> the right method. If you think outstanding total fences
> can never be 0 during decode, then your previous version (v3) itself is
> good, there is no real benefit of splitting the handlers as such.
>
> Regards,
> Sathish
> >
> > If it is possible, maybe it would be easier to just split the profile
> > and powergating into separate handlers. The profile one would be
> > global and the powergating one would be per instance. See the
> > attached patches.
> >
> > Alex
> >
> >> can be a sure shot indication of break in a video decode, the mistake in
> >> my patch was using per instance mutex, I should have used a common
> >> global mutex, then that covers the situation David is trying to bring out.
> >>
> >> Using one global vcn.pg_lock for idle and begin_use and using flags to
> >> track power state could help us totally avoid this situation.
> >>
> >> Regards,
> >>
> >> Sathish
> >>
> >> On 8/13/2025 11:46 PM, Wu, David wrote:
> >>> On 8/13/2025 12:51 PM, Alex Deucher wrote:
> >>>> On Wed, Aug 13, 2025 at 12:39 PM Wu, David <david...@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....@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.sundarar...@amd.com> (v1)
> >>>>>> Signed-off-by: Alex Deucher <alexander.deuc...@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?
> >>> hmm.. OK - no need and it is actually better before the mutex.
> >>> David
> >>>> 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;
