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

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Message-ID: <CAKohpon6DhiWMuszuznK4ZNCBTpy0_r3gGvTXCDMcktXpN3HEw@mail.gmail.com>
Date:	Fri, 8 Nov 2013 10:25:09 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Stratos Karafotis <skarafotis@...il.com>
Cc:	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>,
	Xiaoguang Chen <chenxg.marvell@...il.com>
Subject: Re: [PATCH] cpufreq: conservative: fix requested_freq reduction issue

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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