linux-kernel - Re: [PATCH] cpufreq: cached_resolved

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Date:   Thu, 30 Jul 2020 18:25:59 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Amit Kucheria <amitk@...nel.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Ionela Voinescu <ionela.voinescu@....com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: cached_resolved_idx can not be negative

On Thu, Jul 30, 2020 at 8:41 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 30-07-20, 12:02, Amit Kucheria wrote:
> > Looking at this more closely, I found another call site for
> > cpufreq_frequency_table_target() in cpufreq.c that needs the index to
> > be unsigned int.
> >
> > But then cpufreq_frequency_table_target() returns -EINVAL, so we
>
> It returns -EINVAL only in the case where the relation is not valid,
> which will never happen. Maybe that should be marked with WARN or BUG
> and we should drop return value of -EINVAL.
>
> Rafael ?

Yeah, make it a WARN_ON_ONCE() IMO.

> > should be able to handle int values.
>
> And so no.
>
> > I think you will need to fix the unconditional assignment of
> >     policy->cached_resolved_idx = idx
> > in cpufreq_driver_resolve_freq(). It doesn't check for -EINVAL, so the
> > qcom driver is write in checking for a negative value.
>
> Right, I don't want it to have that check for the reason stated above.
>
> The point is I don't want code that verifies cached-idx at all, it is
> useless.
>
> --
> viresh