linux-kernel - Re: [PATCH v6 1/2] PM / Domains: Add support for 'required-opps' to set default perf state

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Message-ID: <453bdc88-95a3-3798-9a11-ca8038c024ba@gmail.com>
Date:   Wed, 11 Aug 2021 22:48:24 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Rajendra Nayak <rnayak@...eaurora.org>, ulf.hansson@...aro.org,
        bjorn.andersson@...aro.org, viresh.kumar@...aro.org
Cc:     linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        swboyd@...omium.org, rojay@...eaurora.org, stephan@...hold.net
Subject: Re: [PATCH v6 1/2] PM / Domains: Add support for 'required-opps' to
 set default perf state

11.08.2021 12:45, Rajendra Nayak пишет:
>>
>> If you have more than one power domain, then this will override the
>> pstate which was set for a previous domain. This code doesn't feel solid
>> to me, at least a clarifying comment is needed about how it's supposed
>> to work.
> 
> I don't quite understand the concern here, this should work with devices
> having multiple power-domains as well. __genpd_dev_pm_attach gets called
> once per power-domain, and we use the index above to identify the
> power-domain.

The domain core code supports only one domain per device, see what
genpd_set_performance_state() does. This means that the second domain
will set the state of the *first* domain, which doesn't make sense. The
genpd_set_performance_state() will actually fail with -ENODEV for all
domains if you will try to do that.