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

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Date:   Thu, 30 Jul 2020 12:02:27 +0530
From:   Amit Kucheria <amitk@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     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@....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 11:40 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 30-07-20, 11:29, Amit Kucheria wrote:
> > On Thu, Jul 30, 2020 at 9:38 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
> > >
> > > It is not possible for cached_resolved_idx to be invalid here as the
> > > cpufreq core always sets index to a positive value.
> > >
> > > Change its type to unsigned int and fix qcom usage a bit.
> >
> > Shouldn't you fix up idx in cpufreq_driver_resolve_freq() to be
> > unsigned int too?
>
> Yes, merged this into the patch.

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
should be able to handle int values.

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.

>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 0128de3603df..053d72e52a31 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -538,7 +538,7 @@ unsigned int cpufreq_driver_resolve_freq(struct cpufreq_policy *policy,
>         policy->cached_target_freq = target_freq;
>
>         if (cpufreq_driver->target_index) {
> -               int idx;
> +               unsigned int idx;
>
>                 idx = cpufreq_frequency_table_target(policy, target_freq,
>                                                      CPUFREQ_RELATION_L);
>
> --
> viresh