linux-kernel - Re: [PATCH v7 6/7] OPP: Update the bandwidth on OPP frequency changes

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Date:   Thu, 30 Apr 2020 00:35:12 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Georgi Djakov <georgi.djakov@...aro.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Sibi Sankar <sibis@...eaurora.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Evan Green <evgreen@...omium.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 6/7] OPP: Update the bandwidth on OPP frequency changes

On Wed, Apr 29, 2020 at 11:09 PM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 24-04-20, 14:18, Saravana Kannan wrote:
> > My only comment is -- can we drop this patch please? I'd like to use
> > devfreq governors for voting on bandwidth and this will effectively
> > override whatever bandwidth decisions are made by the devfreq
> > governor.
>
> And why would that be better ? FWIW, that will have the same problem
> which cpufreq governors had since ages, i.e. they were not proactive
> and were always too late.
>
> The bw should get updated right with frequency, why shouldn't it ?

I didn't say the bw would be voted based on just CPUfreq. It can also
be based on CPU busy time and other stats. Having said that, this is
not just about CPUfreq. Having the bw be force changed every time a
device has it's OPP is changed is very inflexible. Please don't do it.

-Saravana