linux-kernel - Re: [PATCH V3] cpufreq: reinitialize new policy min/max when writing scaling_(max|min)

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Date:   Wed, 30 May 2018 13:10:55 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Kevin Wangtao <kevin.wangtao@...ilicon.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        gengyanping@...ilicon.com, sunzhaosheng@...ilicon.com
Subject: Re: [PATCH V3] cpufreq: reinitialize new policy min/max when writing scaling_(max|min)_freq

On Wed, May 30, 2018 at 9:56 AM, Kevin Wangtao
<kevin.wangtao@...ilicon.com> wrote:
> consider such situation, current user_policy.min is 1000000,
> current user_policy.max is 1200000, in cpufreq_set_policy,
> other driver may update policy.min to 1200000, policy.max to
> 1300000. After that, If we input "echo 1300000 > scaling_min_freq",
> then user_policy.min will be 1300000, and user_policy.max is
> still 1200000, because the input value is checked with policy.max
> not user_policy.max. if we get all related cpus offline and
> online again, it will cause cpufreq_init_policy fail because
> user_policy.min is higher than user_policy.max.
>
> The solution is when user space tries to write scaling_(max|min)_freq,
> the min/max of new_policy should be reinitialized with min/max
> of user_policy, like what cpufreq_update_policy does.
>
> Signed-off-by: Kevin Wangtao <kevin.wangtao@...ilicon.com>

I've applied the v2 with modified subject and changelog and with the
ACK from Viresh.

Thanks!