Re: [PATCH V5 RESEND 5/5] venus: pm_helpers: Use dev_pm_genpd_set_hwmode to switch GDSC mode on V6

[Bryan O'Donoghue]

On 14/04/2024 15:52, Jagadeesh Kona wrote:
> On 4/14/2024 6:09 PM, Bryan O'Donoghue wrote:
> > On 13/04/2024 16:20, Jagadeesh Kona wrote:
> > > The Venus driver requires vcodec GDSC to be ON in SW mode for clock
> > > operations and move it back to HW mode to gain power benefits. Earlier,
> > > as there is no interface to switch the GDSC mode from GenPD framework,
> > > the GDSC is moved to HW control mode as part of GDSC enable callback and
> > > venus driver is writing to its POWER_CONTROL register to keep the 
> > > GDSC ON
> > > from SW whereever required. But the POWER_CONTROL register addresses
> > > are not constant and can vary across the variants.
> > >
> > > Also as per the HW recommendation, the GDSC mode switching needs to be
> > > controlled from respective GDSC register and this is a uniform approach
> > > across all the targets. Hence use dev_pm_genpd_set_hwmode() API which
> > > controls GDSC mode switching using its respective GDSC register.
> > >
> > > In venus V6 variants, the vcodec gdsc gets enabled in SW mode by default
> > > with new HW_CTRL_TRIGGER flag and there is no need to switch it to SW
> > > mode again after enable, hence add check to avoid switching gdsc to 
> > > SW mode
> > > again after gdsc enable. Similarly add check to avoid switching GDSC 
> > > to HW
> > > mode before disabling the GDSC, so GDSC gets enabled in SW mode in 
> > > the next
> > > enable.
> > >
> > > Signed-off-by: Jagadeesh Kona <quic_jkona@xxxxxxxxxxx>
> > > Signed-off-by: Abel Vesa <abel.vesa@xxxxxxxxxx>
> > > ---
> >
> > When I tested this out on sm8250 a few months ago it was broken.
> >
> > I don't quite see in your commit logs, how the breakage was addressed.
> >
> > Can you provide some details ?
>
> Thanks Bryan for your review!
>
> In earlier series, venus driver is switching the vcodec GDSC to HW 
> control mode before disabling the GDSC by invoking 
> vcodec_control_v4(..., false) in poweroff_coreid(). Due to this, the 
> subsequent GDSC enable from venus driver is failing while polling for 
> GDSC power ON status, since GDSC is under HW control mode and HW can 
> keep the GDSC in disabled state.
>
> Now a check is added in poweroff_coreid() to avoid switching the GDSC to 
> HW control mode before disabling the GDSC for Venus V6 variants that use 
> this new API. Hence during the next GDSC enable, GDSC will be in SW mode 
> and GDSC will powerup properly.

Right so the intention is to have HW GDSC control during playback only - 
and then revert to SW control when no stream is active, right ?

I tried your series on today's -next.

Here is -next without your changes

https://drive.google.com/file/d/1PFuLOlEp582rBQUvuwc9PNZUBxn1ioYf/view?usp=sharing

and here is -next with your changes

https://drive.google.com/file/d/1PHR4rZnWUH9Wp2B-itT5yCUXIMOMZrwM/view?usp=sharing

The first time I tried that test the stopping/stuttering was worse.

So yes the original crash was fixed but, this looks like a performance 
regression to me.

Here's the tree I tested with.

https://git.codelinaro.org/bryan.odonoghue/kernel/-/tree/linux-next-24-05-23-review?ref_type=heads

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bod