linux-kernel - Re: [PATCH] thermal/cpu_cooling: remove local cooling state variable

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Date:	Mon, 3 Aug 2015 08:43:25 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Radivoje Jovanovic <radivoje.jovanovic@...ux.intel.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Punit Agrawal <punit.agrawal@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PM <linux-pm@...r.kernel.org>,
	Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Radivoje Jovanovic <radivoje.jovanovic@...el.com>
Subject: Re: [PATCH] thermal/cpu_cooling: remove local cooling state variable

On 01-08-15, 17:04, Viresh Kumar wrote:
> On 31-07-15, 08:30, Radivoje Jovanovic wrote:

> > I agree with you that this patch is trivial for the current
> > implementation since the notifier, as it is currently, will enforce
> > cpu_cooling policy change at every CPUFREQ_ADJUST which would cause
> > problems in our current implementation. In our implementation there is
> > a cpufreq driver that will also change policies during CPUFREQ_ADJUST,
> > once the request comes from the underlying FW so there would be a fight
> > who gets there first since cpu_cooling will change the policy in
> > CPUFREQ_ADJUST notifier_chain and the driver would do the same thing.

Okay, I had a detailed look this morning. cpufreq-notifier is designed
this way that policy->max can be updated by drivers.. So, that's fine.

Now coming to your problem. So, there are two users: fw and thermal,
which can affect policy->max. Now, both of them need to respect the
limits set by others and only decrease policy->max from the notifier
if it doesn't suit them.

I think it should work pretty well, unless you know you have triggered
a corner case somewhere, that I am not able to imagine.

Please let me know in case I am wrong.

-- 
viresh
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