linux-kernel - Re: [RESEND][PATCH v2 4/4] soc: samsung: exynos-asv: Update Energy Model after adjusting voltage

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Date: Wed, 27 Mar 2024 13:56:09 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Lukasz Luba <lukasz.luba@....com>
Cc: linux-arm-kernel@...ts.infradead.org, sboyd@...nel.org, nm@...com,
 linux-samsung-soc@...r.kernel.org, daniel.lezcano@...aro.org,
 rafael@...nel.org, viresh.kumar@...aro.org, krzysztof.kozlowski@...aro.org,
 alim.akhtar@...sung.com, m.szyprowski@...sung.com, mhiramat@...nel.org,
 linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [RESEND][PATCH v2 4/4] soc: samsung: exynos-asv: Update Energy
 Model after adjusting voltage

On 26/03/2024 21:12, Lukasz Luba wrote:
> Hi Dietmar,
> 
> On 3/26/24 11:20, Dietmar Eggemann wrote:
>> On 22/03/2024 12:08, Lukasz Luba wrote:
>>
>> [...]
>>
>>> @@ -97,9 +98,17 @@ static int exynos_asv_update_opps(struct
>>> exynos_asv *asv)
>>>               last_opp_table = opp_table;
>>>                 ret = exynos_asv_update_cpu_opps(asv, cpu);
>>> -            if (ret < 0)
>>> +            if (!ret) {
>>> +                /*
>>> +                 * When the voltage for OPPs successfully
>>> +                 * changed, update the EM power values to
>>> +                 * reflect the reality and not use stale data
>>
>> At this point, can we really say that the voltage has changed?
>>
>>    exynos_asv_update_cpu_opps()
>>
>>      ...
>>      ret = dev_pm_opp_adjust_voltage()
>>      if (!ret)
>>        em_dev_update_chip_binning()
>>      ...
>>
>> dev_pm_opp_adjust_voltage() also returns 0 when the voltage value stays
>> the same?
>>
>> [...]
> 
> The comment for the dev_pm_opp_adjust_voltage() says that it
> returns 0 if no modification was done or modification was
> successful. So I cannot distinguish in that driver code, but
> also there is no additional need to do it IMO (even framework
> doesn't do this).

Precisely. That's why the added comment in exynos_asv_update_opps():
"When the voltage for OPPs successfully __changed__, ..." is somehow
misleading IMHO.