linux-kernel - Re: [PATCH v2] cpufreq: arm_big_little: fix frequency check when bL switcher is active

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Date:	Thu, 05 Nov 2015 23:46:21 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	"Jon Medhurst (Tixy)" <tixy@...aro.org>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>,
	Sudeep Holla <sudeep.holla@....com>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Michael Turquette <mturquette@...libre.com>
Subject: Re: [PATCH v2] cpufreq: arm_big_little: fix frequency check when bL switcher is active

On Saturday, October 31, 2015 03:34:05 AM Rafael J. Wysocki wrote:
> On Friday, October 30, 2015 10:48:18 AM Jon Medhurst wrote:
> > On Wed, 2015-10-21 at 15:27 +0530, Viresh Kumar wrote:
> > > On 21-10-15, 10:55, Jon Medhurst (Tixy) wrote:
> > > > The check for correct frequency being set in bL_cpufreq_set_rate is
> > > > broken when the big.LITTLE switcher is active, for two reasons.
> > > > 
> > > > 1. The 'new_rate' variable gets overwritten before the test by the
> > > > code calculating the frequency of the old cluster.
> > > > 
> > > > 2. The frequency returned by bL_cpufreq_get_rate will be the virtual
> > > > frequency, not the actual one the intended version of new_rate contains.
> > > > 
> > > > This means the function always returns an error causing an endless
> > > > stream of: "cpufreq: __target_index: Failed to change cpu frequency: -5"
> > > > 
> > > > As the intent is to check for errors that clk_set_rate doesn't report
> > > > lets move the check to immediately after that and directly use
> > > > clk_get_rate, rather than the arm_big_little helpers which only confuse
> > > > matters. Also, update the comment to be hopefully clearer about the
> > > > purpose of the code.
> > > > 
> > > > Fixes: 0a95e630b49a ("cpufreq: arm_big_little: check if the frequency is set correctly")
> > > > 
> > > > Signed-off-by: Jon Medhurst <tixy@...aro.org>
> > > > Acked-by: Sudeep Holla <sudeep.holla@....com>
> > > > ---
> > > > 
> > [...]
> > > 
> > > Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> > > 
> > 
> > Do I need to send this again with that Ack and Michael's Reviewed-by
> > added?
> 
> Nope, it's on my to-do list.

Applied now, thanks!

Rafael

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