linux-kernel - Re: [Patch 1/6] cpufreq: use correct unit when verify cur freq

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Date:   Tue, 18 Apr 2023 17:47:06 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Sumit Gupta <sumitg@...dia.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>, viresh.kumar@...aro.org,
        ionela.voinescu@....com, mark.rutland@....com,
        sudeep.holla@....com, lpieralisi@...nel.org,
        catalin.marinas@....com, will@...nel.org, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org, treding@...dia.com,
        jonathanh@...dia.com, vsethi@...dia.com, sdonthineni@...dia.com,
        sanjayc@...dia.com, ksitaraman@...dia.com, bbasu@...dia.com
Subject: Re: [Patch 1/6] cpufreq: use correct unit when verify cur freq

On Tue, Apr 18, 2023 at 3:32 PM Sumit Gupta <sumitg@...dia.com> wrote:
>
>
>
> On 18/04/23 18:27, Rafael J. Wysocki wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > On Tue, Apr 18, 2023 at 1:35 PM Sumit Gupta <sumitg@...dia.com> wrote:
> >>
> >> From: Sanjay Chandrashekara <sanjayc@...dia.com>
> >>
> >> cpufreq_verify_current_freq checks if the frequency returned by
> >> the hardware has a slight delta with the valid frequency value
> >> last set and returns "policy->cur" if the delta is within "1 MHz".
> >> In the comparison, "policy->cur" is in "kHz" but it's compared
> >> against HZ_PER_MHZ. So, the comparison range becomes "1 GHz".
> >> Fix this by comparing against KHZ_PER_MHZ instead of HZ_PER_MHZ.
> >>
> >> Fixes: f55ae08c8987 ("cpufreq: Avoid unnecessary frequency updates due to mismatch")
> >> Signed-off-by: Sanjay Chandrashekara <sanjayc@...dia.com>
> >> [ sumit gupta: Commit message update ]
> >> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
> >> ---
> >>   drivers/cpufreq/cpufreq.c | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> >> index 8b0509f89f1b..6b52ebe5a890 100644
> >> --- a/drivers/cpufreq/cpufreq.c
> >> +++ b/drivers/cpufreq/cpufreq.c
> >> @@ -1732,7 +1732,7 @@ static unsigned int cpufreq_verify_current_freq(struct cpufreq_policy *policy, b
> >>                   * MHz. In such cases it is better to avoid getting into
> >>                   * unnecessary frequency updates.
> >>                   */
> >> -               if (abs(policy->cur - new_freq) < HZ_PER_MHZ)
> >> +               if (abs(policy->cur - new_freq) < KHZ_PER_MHZ)
> >>                          return policy->cur;
> >>
> >>                  cpufreq_out_of_sync(policy, new_freq);
> >> --
> >
> > So this is a fix that can be applied separately from the rest of the
> > series, isn't it?
>
> Yes.

So applied as 6.4 material.