linux-kernel - Re: [PATCH] cpufreq: conservative: Fix next frequency selection

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Message-ID: <20161013062616.GC2991@vireshk-i7>
Date:   Thu, 13 Oct 2016 11:56:16 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM list <linux-pm@...r.kernel.org>,
        Aleksey Rybalkin <aleksey@...alkin.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH] cpufreq: conservative: Fix next frequency selection

On 12-10-16, 21:47, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Commit d352cf47d93e (cpufreq: conservative: Do not use transition
> notifications) overlooked the case when the "frequency step" used
> by the conservative governor is small relative to the distances
> between the available frequencies and broke the algorithm by
> using policy->cur instead of the previously requested frequency
> when computing the next one.
> 
> As a result, the governor may not be able to go outside of a narrow
> range between two consecutive available frequencies.
> 
> Fix the problem by making the governor save the previously requested
> frequency and select the next one relative that value (unless it is
> out of range, in which case policy->cur will be used instead).
> 
> Fixes: d352cf47d93e (cpufreq: conservative: Do not use transition notifications)
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=177171
> Reported-and-tested-by: Aleksey Rybalkin <aleksey@...alkin.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/cpufreq/cpufreq_conservative.c |   19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh