linux-kernel - Re: [PATCH] cpufreq: Fix cpufreq regression after suspend/resume

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Message-ID: <51DDC8FA.4020609@gmx.de>
Date:	Wed, 10 Jul 2013 22:50:02 +0200
From:	Toralf Förster <toralf.foerster@....de>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	cpufreq@...r.kernel.org, Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: Fix cpufreq regression after suspend/resume

I tested the patch several times on top of a66b2e5 - the origin issue is
fixed but - erratically another issue now appears : all 4 cores are runs
after wakeup at 2.6 GHz.
The temporary hot fix is to switch between governor performance and
ondemand for all 4 cores.


On 06/30/2013 08:52 PM, Srivatsa S. Bhat wrote:
> On 06/30/2013 10:35 PM, Toralf Förster wrote:
>> On 06/30/2013 06:33 PM, Srivatsa S. Bhat wrote:
>>> Toralf, can you please
>>> try out the below patch and see if it improves anything? (Don't revert anything,
>>> just apply the below diff on a problematic kernel and see if it solves your
>>> issue).
>>
>> applied on top of a66b2e5 - issue went away (either fixed or hidden now)
>>
> 
> Cool! So here is the proper patch, with changelog added.
> 
> Regards,
> Srivatsa S. Bhat
> 
> 
> -----------------------------------------------------------------------------
> 
> From: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> Subject: [PATCH] cpufreq: Fix cpufreq regression after suspend/resume
> 
> Toralf Förster reported that the cpufreq ondemand governor behaves erratically
> (doesn't scale well) after a suspend/resume cycle. The problem was that the
> cpufreq subsystem's idea of the cpu frequencies differed from the actual
> frequencies set in the hardware after a suspend/resume cycle. Toralf bisected
> the problem to commit a66b2e5 (cpufreq: Preserve sysfs files across
> suspend/resume).
> 
> Among other (harmless) things, that commit skipped the call to
> cpufreq_update_policy() in the resume path. But cpufreq_update_policy() plays
> an important role during resume, because it is responsible for checking if
> the BIOS changed the cpu frequencies behind our back and resynchronize the
> cpufreq subsystem's knowledge of the cpu frequencies, and update them
> accordingly.
> 
> So, restore the call to cpufreq_update_policy() in the resume path to fix
> the cpufreq regression.
> 
> Reported-by: Toralf Förster <toralf.foerster@....de>
> Tested-by: Toralf Förster <toralf.foerster@....de>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> ---
> 
>  drivers/cpufreq/cpufreq_stats.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
> index fb65dec..591b6fb 100644
> --- a/drivers/cpufreq/cpufreq_stats.c
> +++ b/drivers/cpufreq/cpufreq_stats.c
> @@ -349,6 +349,7 @@ static int __cpuinit cpufreq_stat_cpu_callback(struct notifier_block *nfb,
>  
>  	switch (action) {
>  	case CPU_ONLINE:
> +	case CPU_ONLINE_FROZEN:
>  		cpufreq_update_policy(cpu);
>  		break;
>  	case CPU_DOWN_PREPARE:
> 
> 
> 


-- 
MfG/Sincerely
Toralf Förster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3
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