linux-kernel - Re: [PATCH V5 RESEND 5/5] venus: pm_helpers: Use dev_pm_genpd_set

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Date: Wed, 24 Apr 2024 01:16:26 +0100
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Jagadeesh Kona <quic_jkona@...cinc.com>,
 Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
 Bjorn Andersson <andersson@...nel.org>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Stanimir Varbanov <stanimir.k.varbanov@...il.com>,
 Vikash Garodia <quic_vgarodia@...cinc.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Ulf Hansson <ulf.hansson@...aro.org>, "Rafael J . Wysocki"
 <rafael@...nel.org>, Kevin Hilman <khilman@...nel.org>,
 Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Konrad Dybcio <konrad.dybcio@...aro.org>, Andy Gross <agross@...nel.org>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Abel Vesa <abel.vesa@...aro.org>
Cc: linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 linux-pm@...r.kernel.org, Taniya Das <quic_tdas@...cinc.com>,
 Satya Priya Kakitapalli <quic_skakitap@...cinc.com>,
 Imran Shaik <quic_imrashai@...cinc.com>,
 Ajit Pandey <quic_ajipan@...cinc.com>
Subject: Re: [PATCH V5 RESEND 5/5] venus: pm_helpers: Use
 dev_pm_genpd_set_hwmode to switch GDSC mode on V6

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@...cinc.com>
>>> Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
>>> ---
>>
>> 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

---
bod