linux-kernel - Re: [PATCH] cpufreq: longhaul: Set transition_delay

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Date:   Tue, 28 Nov 2017 23:07:36 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Meelis Roos <mroos@...ux.ee>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "4 . 14+" <stable@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: longhaul: Set transition_delay_us to 20 ms

On Tue, Nov 28, 2017 at 4:11 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> The commit e948bc8fbee0 ("cpufreq: Cap the default transition delay
> value to 10 ms") caused a regression on EPIA-M min-ITX computer where
> shutdown or reboot hangs occasionally with a print message like:
>
> longhaul: Warning: Timeout while waiting for idle PCI bus
> cpufreq: __target_index: Failed to change cpu frequency: -16
>
> This probably happens because the cpufreq governor tries to change the
> frequency of the CPU faster than allowed by the hardware.
>
> With the above commit, the default transition delay comes to 10 ms for a
> transition_latency of 200 us. Set the default transition delay to 20 ms
> directly to fix this regression.
>
> Fixes: e948bc8fbee0 ("cpufreq: Cap the default transition delay value to 10 ms")
> Cc: 4.14+ <stable@...r.kernel.org> # 4.14+
> Reported-by: Meelis Roos <mroos@...ux.ee>
> Suggested-by: Rafael J. Wysocki <rjw@...ysocki.net>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/cpufreq/longhaul.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/longhaul.c b/drivers/cpufreq/longhaul.c
> index c46a12df40dd..56eafcb07859 100644
> --- a/drivers/cpufreq/longhaul.c
> +++ b/drivers/cpufreq/longhaul.c
> @@ -894,7 +894,7 @@ static int longhaul_cpu_init(struct cpufreq_policy *policy)
>         if ((longhaul_version != TYPE_LONGHAUL_V1) && (scale_voltage != 0))
>                 longhaul_setup_voltagescaling();
>
> -       policy->cpuinfo.transition_latency = 200000;    /* nsec */
> +       policy->transition_delay_us = 20000;    /* usec */
>
>         return cpufreq_table_validate_and_show(policy, longhaul_table);
>  }
> --

Meelis, please check if this fixes the shutdown issue you have
reported recently.

Thanks,
Rafael