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

From: Vincent Guittot <vincent.guittot@linaro.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Rafael Wysocki <rjw@rjwysocki.net>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	linux-pm@vger.kernel.org, Rex-BC Chen <rex-bc.chen@mediatek.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org
Subject: Re: [PATCH] cpufreq: Avoid unnecessary frequency updates due to mismatch
Date: Thu, 5 May 2022 11:40:28 +0200	[thread overview]
Message-ID: <CAKfTPtCfKBiQkghY6gw+sSYYOXFRWMZNXsr64Vn5G-Oo1HF8ew@mail.gmail.com> (raw)
In-Reply-To: <20220505082801.oks7ko2sbqazyenn@vireshk-i7>

On Thu, 5 May 2022 at 10:28, Viresh Kumar <viresh.kumar@linaro.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