linux-kernel - Re: [PATCH 1/2] OPP: Add API to update EM after adjustment of voltage for OPPs

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Date: Thu, 4 Jan 2024 10:38:43 +0000
From: Lukasz Luba <lukasz.luba@....com>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
 dietmar.eggemann@....com, linux-arm-kernel@...ts.infradead.org,
 sboyd@...nel.org, nm@...com, linux-samsung-soc@...r.kernel.org,
 daniel.lezcano@...aro.org, rafael@...nel.org,
 krzysztof.kozlowski@...aro.org, alim.akhtar@...sung.com,
 m.szyprowski@...sung.com, xuewen.yan94@...il.com, mhiramat@...nel.org,
 qyousef@...alina.io, wvw@...gle.com
Subject: Re: [PATCH 1/2] OPP: Add API to update EM after adjustment of voltage
 for OPPs

Hi Viresh,

On 12/26/23 05:12, Viresh Kumar wrote:
> On 20-12-23, 11:03, Lukasz Luba wrote:
>> There are device drivers which can modify voltage values for OPPs. It
>> could be due to the chip binning and those drivers have specific chip
>> knowledge about this. This adjustment can happen after Energy Model is
>> registered, thus EM can have stale data about power.
>>
>> Introduce new API function which can be used by device driver which
>> adjusted the voltage for OPPs. The implementation takes care about
>> calculating needed internal details in the new EM table ('cost' field).
>> It plugs in the new EM table to the framework so other subsystems would
>> use the correct data.
>>
>> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
>> ---
>>   drivers/opp/of.c       | 69 ++++++++++++++++++++++++++++++++++++++++++
>>   include/linux/pm_opp.h |  6 ++++
>>   2 files changed, 75 insertions(+)
>>
>> diff --git a/drivers/opp/of.c b/drivers/opp/of.c
>> index 81fa27599d58..992434c0b711 100644
>> --- a/drivers/opp/of.c
>> +++ b/drivers/opp/of.c
>> @@ -1596,3 +1596,72 @@ int dev_pm_opp_of_register_em(struct device *dev, struct cpumask *cpus)
>>   	return ret;
>>   }
>>   EXPORT_SYMBOL_GPL(dev_pm_opp_of_register_em);
>> +
>> +/**
>> + * dev_pm_opp_of_update_em() - Update Energy Model with new power values
>> + * @dev		: Device for which an Energy Model has to be registered
>> + *
>> + * This uses the "dynamic-power-coefficient" devicetree property to calculate
>> + * power values for EM. It uses the new adjusted voltage values known for OPPs
>> + * which have changed after boot.
>> + */
>> +int dev_pm_opp_of_update_em(struct device *dev)
> 
> I don't see anything OPP or OF related in this function, I don't think it needs
> to be part of the OPP core. You just want to reuse _get_power() I guess, which
> can be exported then.
> 
> This should really be part of the EM core instead.
> 

Thank you for having a look at this. OK, that makes sense.
When I finish the EM runtime modification core features and get them
merged, I'll continue to work on this patch set. I'll try to follow
your comment here and export that function (with a different name
probably).

Regards,
Lukasz