Re: [PATCH] cpufreq: longhaul: Set transition_delay_us to 20 ms

[Meelis Roos <mroos@linux.ee>]

> 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@vger.kernel.org> # 4.14+
> Reported-by: Meelis Roos <mroos@linux.ee>
> Suggested-by: Rafael J. Wysocki <rjw@rjwysocki.net>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.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);
>  }

This patch also works on my EPIA-M board - tested 10+ times.

Sorry it took so long to test, it was a remote computer.

-- 
Meelis Roos (mroos@linux.ee)