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

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Date:   Tue, 19 Jan 2021 15:25:11 +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 19-01-21, 10:52, Ulf Hansson wrote:
> That would work if the topology is built from top to bottom, but I
> don't think we can rely on that.
> 
> For example, when a domain A is added as a child to domain B, domain B
> doesn't have a parent yet (and the "can-handle-pstates" don't get set
> for neither domain A or domain B). Next, domain B is added as child
> domain to domain C. Domain C has the "can-handle-pstates" set, which
> means domain B gets the "can-handle-pstates" set as well. This means
> domain A, will not have "can-handle-pstates" set, while it probably
> should have.

Okay, I missed that part.

> >
> > > So, maybe we should simply just stick to the existing code, forcing
> > > the parent to have a ->set_performance() callback assigned if
> > > propagation should continue?
> >
> > I think it would be better to fix the issue even if we aren't fully optimized
> > and making the change to make sure we keep propagating is rather important.
> 
> Alright, let's continue with Dmitry's patches and discuss this further
> when v4 is out, as he seems to have it almost ready.

Right.

-- 
viresh