linux-kernel - Re: [PATCHv9 1/3] Runtime Interpreted Power Sequences

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Message-ID: <50AC956D.7020303@ti.com>
Date:	Wed, 21 Nov 2012 10:48:45 +0200
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Alex Courbot <acourbot@...dia.com>
CC:	Anton Vorontsov <cbouatmailru@...il.com>,
	Stephen Warren <swarren@...dia.com>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	Mark Zhang <markz@...dia.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCHv9 1/3] Runtime Interpreted Power Sequences

On 2012-11-21 10:32, Alex Courbot wrote:

>> Ok. I'll need to dig up the conversation
> 
> IIRC it was somewhere around here:
> 
> https://lkml.org/lkml/2012/9/7/662
> 
> See the parent messages too.

Thanks.

>> Did you consider any examples
>> of how some driver could handle the error cases?
> 
> For all the (limited) use cases I considered, playing the power-off sequence 
> when power-on fails just works. If power-off also fails you are potentially in 
> more trouble though. Maybe we could have another "run" function that does not 
> stop on errors for handling such cases where you want to "stop everything you 
> can".

If the power-off sequence disables a regulator that was supposed to be
enabled by the power-on sequence (but wasn't enabled because of an
error), the regulator_disable is still called when the driver runs the
power-off sequence, isn't it? Regulator enables and disables are ref
counted, and the enables should match the disables.

> Failures might be better handled if sequences have some "recovery policy" 
> about what to do when they fail, as mentioned in the link above. As you 
> pointed out, the driver might not always know enough about the resources 
> involved to do the right thing.

Yes, I think such recovery policy would be needed.

 Tomi



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