linux-kernel - Re: [PATCH 5/8] thermal:cpu cooling:tegra: Provide deferred probing for tegra driver

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Date:	Mon, 17 Nov 2014 14:02:45 +0100
From:	Lukasz Majewski <l.majewski@...sung.com>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Mikko Perttunen <mikko.perttunen@...si.fi>,
	Eduardo Valentin <edubezval@...il.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Vincenzo Frascino <vincenzo.frascino@...com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Lukasz Majewski <l.majewski@...ess.pl>,
	Nobuhiro Iwamatsu <iwamatsu@...auri.org>,
	Mikko Perttunen <mperttunen@...dia.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Alexandre Courbot <gnurou@...il.com>,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/8] thermal:cpu cooling:tegra: Provide deferred probing
 for tegra driver

Hi Thierry,

> On Mon, Nov 17, 2014 at 12:50:13PM +0100, Lukasz Majewski wrote:
> > Hi Thierry,
> > 
> > > On Fri, Nov 14, 2014 at 12:47:33PM +0200, Mikko Perttunen wrote:
> > > > Tested-by: Mikko Perttunen <mikko.perttunen@...si.fi>
> > > > 
> > > > One potential issue I can see is that if the cpufreq driver
> > > > fails to probe then you'll never get the thermal driver either.
> > > > For example, Tegra124 currently has no cpufreq driver, so if
> > > > CONFIG_CPU_THERMAL was enabled, then the soctherm driver would
> > > > never be able to probe. But I don't really have a solution for
> > > > this either.
> > > 
> > > It doesn't seem like there's any code whatsoever to deal with
> > > cpufreq within the soctherm driver, so deferring probe based on
> > > something we're not using anyway seems rather useless.
> > 
> > So, If I understood you correctly - this patch is not needed in the 
> > /tegra_soctherm.c:[tegra_defconfig] driver and can be safely
> > omitted in v2 of this driver.
> 
> What I'm saying is that I don't think doing this mass conversion
> wholesale is useful since none of the drivers register a cooling
> device based on cpufreq. In other words: if you're not going to use a
> feature there's no use testing for it.
> 

It seems, like one option here would be to add deferred proble to
cpufreq_cooling_register() or check which driver in its thermal probe
is calling cpufreq_cooling_register() function.

The latter option explains why in the imx_thermal.c file we check for
deferred probe without #ifdefs for CONFIG_CPU_THERMAL.

If no objections, I would like to stick to the code already available
in imx_thermal.c.

> Thierry

-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group
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