linux-kernel - Re: [PATCH V2] cpufreq: Make sure CPU is running on a freq from freq-table

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Message-ID: <2309056.KUZA1Fnj0Y@vostro.rjw.lan>
Date:	Tue, 26 Nov 2013 21:21:23 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Dirk Brandewie <dirk.brandewie@...il.com>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Patch Tracking <patches@...aro.org>,
	"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>,
	Nishanth Menon <nm@...com>, Carlos Hernandez <ceh@...com>
Subject: Re: [PATCH V2] cpufreq: Make sure CPU is running on a freq from freq-table

On Tuesday, November 26, 2013 07:31:50 AM Viresh Kumar wrote:
> On 26 November 2013 02:43, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> > On Monday, November 25, 2013 09:43:59 AM Dirk Brandewie wrote:
> >> This is a platform specific bug fix AFAICT and belongs in a platform
> >> specific piece of code
> 
> In case we end up doing that, we will do lots of code redundancy in
> cpufreq drivers. And as Rafael said, some platforms might never
> know they have booted with an out of table frequency and so taking
> care of this at a single place is better, where we are sure that it
> will get fixed.
> 
> >> The core should not be working around bootloader bugs IMHO.  Silently
> >> fixing it is evil IMHO at a minimum the core should complain LOUDLY
> >> about this happening otherwise the bootloaders will have no incentive to
> >> get their act together.
> 
> That looks correct..
> 
> > Yes, we can add a WARN_ON() there.  Still, though, the core's responsibility
> > is to ensure that (a) either we can continue safely or (b) we can't, in which
> > case it should just fail the initialization.  Whether or not it should panic()
> > I'm not sure.
> 
> But is this that big crime, that we do a WARN on it? CPU was running on
> a workable frequency, it wasn't mentioned in the table, that's it.
> 
> Probably just throw an print message that CPU found to be running on
> out of table frequency, and that got fixed..

I was talking about the case when your

__cpufreq_driver_target(policy, policy->cur - 1, CPUFREQ_RELATION_L);

fails.  The other case is not really interesting.

Thanks!

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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