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

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Date: Tue, 26 Mar 2024 20:12:59 +0000
From: Lukasz Luba <lukasz.luba@....com>
To: Dietmar Eggemann <dietmar.eggemann@....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

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).

Regards,
Lukasz

[1] 
https://elixir.bootlin.com/linux/v6.9-rc1/source/drivers/opp/core.c#L2950