linux-kernel - Re: [PATCH] cpufreq: cpufreq_stats: make last

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Message-ID: <20170919185447.GC30848@ubuntu>
Date:   Tue, 19 Sep 2017 11:54:47 -0700
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Bo Yan <byan@...dia.com>
Cc:     rjw@...ysocki.net, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: cpufreq_stats: make last_index signed int

On 18-09-17, 10:39, Bo Yan wrote:
> Currently, the "last_index" is being checked before
> cpufreq_stats_update(stats) inside function
> "cpufreq_stats_record_transition", so it's taken care of.
> 
> However, the function "show_time_in_state" also calls cpufreq_stats_update,
> the similar check should be done there too, like this:

Yeah, that's what I suggested.

> diff --git a/drivers/cpufreq/cpufreq_stats.c
> b/drivers/cpufreq/cpufreq_stats.c
> index e75880eb037d..15305b5ec322 100644
> --- a/drivers/cpufreq/cpufreq_stats.c
> +++ b/drivers/cpufreq/cpufreq_stats.c
> @@ -62,7 +62,8 @@ static ssize_t show_time_in_state(struct cpufreq_policy
> *policy, char *buf)
>         if (policy->fast_switch_enabled)
>                 return 0;
> 
> -       cpufreq_stats_update(stats);
> +       if ((int)stats->last_index >= 0)

You can rather do:

        if (stats->last_index != -1)

> +               cpufreq_stats_update(stats);
>         for (i = 0; i < stats->state_num; i++) {
>                 len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i],
>                         (unsigned long long)
> 
> 
> This is only needed when policy->cur is not in frequency table when stats
> table is created, in which case, stats->last_index will get -1, then user
> does a "cat time_in_state" before any frequency transition.
> 
> Does this make sense?

-- 
viresh