linux-kernel - Re: [PATCH v3 1/3] PM: domains: Make set_performance

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Message-ID: <20210118110506.linvsoca7jbl42iq@vireshk-i7>
Date:   Mon, 18 Jan 2021 16:35:06 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matt Merhar <mattmerhar@...tonmail.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] PM: domains: Make set_performance_state()
 callback optional

On 18-01-21, 11:59, Ulf Hansson wrote:
> Good point! I certainly overlooked that when reviewing. We need to
> reevaluate the new state when propagating to the parent(s).
> 
> To me, it looks like when doing the propagation we must check if the
> parent has the ->set_performance_state() callback assigned. If so, we
> should call dev_pm_opp_xlate_performance_state(), but otherwise just
> use the value of "state", when doing the reevaluation.
> 
> Does it make sense?

That will work but I am wondering if there is a way to avoid the
unnecessary propagation if we can somehow find out if someone above in
hierarchy supports pstates or not ?

-- 
viresh