linux-kernel - Re: [PATCH] cpufreq: Avoid unnecessary frequency updates due to mismatch

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Date:   Thu, 5 May 2022 11:40:28 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-pm@...r.kernel.org, Rex-BC Chen <rex-bc.chen@...iatek.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] cpufreq: Avoid unnecessary frequency updates due to mismatch

On Thu, 5 May 2022 at 10:28, Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 05-05-22, 10:21, Vincent Guittot wrote:
> > Part of your problem is that cpufreq use khz whereas clock uses hz
>
> Not in this case at least as the value mentioned in OPP table DT is in
> Hz.

But dev_pm_opp_init_cpufreq_table make it kHz anyway

>
> > Would it be better to do something like below in cpufreq_generic_get
> >
> > (clk_get_rate(policy->clk) + 500) / 1000
> >
> > so you round to closest instead of always floor rounding
>
> That would be a fine thing to do anyway, though I am not sure if it
> will fix the problem at hand.
>
> If the hardware returns 499,999,499 Hz, we will still have the
> problem.

But in this case, cpufreq table should use 499,999Khz IMO. We already
have OPP/cpufreq table being updated at boot with actual value.

>
> --
> viresh