linux-kernel - Re: [PATCH] cpufreq: conservative: fix requested

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Date:	Fri, 8 Nov 2013 13:01:38 +0800
From:	Xiaoguang Chen <chenxg.marvell@...il.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Stratos Karafotis <skarafotis@...il.com>,
	Xiaoguang Chen <chenxg@...vell.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: conservative: fix requested_freq reduction issue

Hi, Viresh, Sorry for the late reply.
I'll prepare the patch.
BTW, do you think we should set requeste_freq to policy->max when such
condition happens?

Thanks
Xiaoguang

2013/11/8 Viresh Kumar <viresh.kumar@...aro.org>:
> On 8 November 2013 00:36, Stratos Karafotis <skarafotis@...il.com> wrote:
>> I think the existing code already checks if the requested_freq is greater
>> than policy->max in __cpufreq_driver_target.
>
> Yes it does. But the problem is:
> - cs_check_cpu() sets requested_freq above policy->max
> - We execute following code because (requested_freq != policy->max)
>
>     dbs_info->requested_freq += get_freq_target(cs_tuners, policy);
>     __cpufreq_driver_target(policy, dbs_info->requested_freq,
> CPUFREQ_RELATION_H);
> - In __cpufreq_driver_target(), we don't do anything and return early..
> - Above will keep on repeating all the time..
>
> If we change the code as I have suggested it to be:
> - After first loop where requested_freq went over policy->max, we will
> return early from cs_check_cpu(), but we have already set freq to max..
>
>> If we put this check earlier, cpufreq will never reach policy->max.
>
> Can you please explain why do you see that happening?
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