Re: [PATCH] cpufreq: reinitialize new policy min/max when writing scaling_(max|min)_freq

[Rafael J. Wysocki]

On Friday, May 25, 2018 4:54:04 AM CEST Wangtao (Kevin, Kirin) wrote:
> 
> å 2018/5/24 15:45, Rafael J. Wysocki åé:
> > On Thu, May 24, 2018 at 8:43 AM, Kevin Wangtao
> > <kevin.wangtao@xxxxxxxxxxxxx> 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.
> > 
> > How do you reproduce this, exactly?
>
> I write a driver register CPUFREQ_POLICY_NOTIFIER, and when event is CPUFREQ_ADJUST,
> it will modify policy's min/max according to some conditions, I test it with writing
> scaling_(max|min)_freq to traverse all frequencies repeatly, and also repeat hotplug
> as background.

You are expected to use cpufreq_update_policy() to update the limits in policy
notifiers.  Do you use it in your driver?