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

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Date:	Sat, 31 Oct 2015 03:34:05 +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 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.

Thanks,
Rafael

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