[PATCH] drm/amdgpu: properly powergate Polaris12 UVD/VCE on suspend

[Quan, Evan]

[AMD Official Use Only]

+Leo to share his insights

> -----Original Message-----
> From: Lazar, Lijo <Lijo.Lazar at amd.com>
> Sent: Tuesday, August 17, 2021 3:28 PM
> To: Quan, Evan <Evan.Quan at amd.com>; amd-gfx at lists.freedesktop.org
> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Chen, Guchun
> <Guchun.Chen at amd.com>; Pan, Xinhui <Xinhui.Pan at amd.com>
> Subject: Re: [PATCH] drm/amdgpu: properly powergate Polaris12 UVD/VCE
> on suspend
> 
> 
> 
> On 8/17/2021 12:10 PM, Evan Quan wrote:
> > If the powergating of UVD/VCE is in process, wait for its completion
> > before proceeding(suspending). This can fix some hangs observed on
> > suspending when UVD/VCE still using(e.g. issue "pm-suspend" when video
> > is still playing).
> >
> > Change-Id: I36f39d9731e0a9638b52d5d92558b0ee9c23a9ed
> > Signed-off-by: Evan Quan <evan.quan at amd.com>
> > Signed-off-by: xinhui pan <xinhui.pan at amd.com>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/uvd_v6_0.c | 5 +++++
> >   drivers/gpu/drm/amd/amdgpu/vce_v3_0.c | 5 +++++
> >   2 files changed, 10 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/uvd_v6_0.c
> > b/drivers/gpu/drm/amd/amdgpu/uvd_v6_0.c
> > index 4eebf973a065..2fdce572baeb 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/uvd_v6_0.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/uvd_v6_0.c
> > @@ -554,6 +554,11 @@ static int uvd_v6_0_suspend(void *handle)
> >   	int r;
> >   	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
> >
> > +	/*
> > +	 * If the powergating is in process, wait for its completion.
> > +	 */
> > +	flush_delayed_work(&adev->uvd.idle_work);
> > +
> If running idle is a prerequisite before going to suspend, then something else
> is missing here.
> 
> Otherwise, the hang looks more like a pending work launched after
> hardware is suspended and trying to access hardware. As the hardware is
> going to be suspended anyway, doesn't it work with
> cancel_delayed_work_sync - making sure that nothing is going to be
> launched later to access hardware?
[Quan, Evan] The reason we chose flush_delayed_work instead of cancel_delayed_work_sync is we think those operations performed in idle_work(dpm disablement, powergating) seems needed considering the action is 'suspend'. So, instead of "cancel", maybe waiting for them completion is more proper. 
> 
> Then this may be a potential issue for other suspend calls also where work is
> pending to be launched when hardware is suspended.
[Quan, Evan] Do you mean we need to check whether there is similar issue for other IPs?

BR
Evan
> 
> Thanks,
> Lijo
> 
> >   	r = uvd_v6_0_hw_fini(adev);
> >   	if (r)
> >   		return r;
> > diff --git a/drivers/gpu/drm/amd/amdgpu/vce_v3_0.c
> > b/drivers/gpu/drm/amd/amdgpu/vce_v3_0.c
> > index 6d9108fa22e0..f0adecd5ec0b 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/vce_v3_0.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/vce_v3_0.c
> > @@ -503,6 +503,11 @@ static int vce_v3_0_suspend(void *handle)
> >   	int r;
> >   	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
> >
> > +	/*
> > +	 * If the powergating is in process, wait for its completion.
> > +	 */
> > +	flush_delayed_work(&adev->vce.idle_work);
> > +
> >   	r = vce_v3_0_hw_fini(adev);
> >   	if (r)
> >   		return r;
> >