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From: Mason <slash.tmp@free.fr>
To: Kevin Hilman <khilman@baylibre.com>
Cc: Eduardo Valentin <edubezval@gmail.com>,
	Javi Merino <javi.merino@arm.com>,
	linux-pm <linux-pm@vger.kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Sebastian Frias <sf84@laposte.net>,
	Thibaud Cornic <thibaud_cornic@sigmadesigns.com>
Subject: Re: [RFC] Adding PM support to thermal driver
Date: Fri, 17 Jun 2016 13:11:54 +0200	[thread overview]
Message-ID: <5763DAFA.6060008@free.fr> (raw)
In-Reply-To: <m2eg7ynmt3.fsf@baylibre.com>

On 15/06/2016 23:51, Kevin Hilman wrote:

> Mason writes:
> 
>> I need to support suspend-to-RAM in my platform.
>> This platform powers down on suspend, so the contents of device registers are lost.
>> Can you tell me if this patch looks OK for adding S2R support?
> 
> The idea looks right for ensuring a clean resume after context loss.

Thanks for your quick review.

> However, I'm a bit surprised to see an empty ->suspend hook though.
> Is there nothing to do to gracefully shutdown this hardware?  A quick
> glance suggests maybe CMD_OFF should be sent?

We discussed this internally. When Linux asks to be suspended to RAM,
the firmware cuts the power to the entire platform (except RAM obviously,
and a few blocks listening for wakeup events).

So it seems pointless to write code to power individual HW blocks down
that are about to be powered down globally.

(NB: the thermal block dissipates ~50 microwatts, so powering it down
ASAP saves only a negligible amount of energy.)

Regards.


      reply	other threads:[~2016-06-17 11:12 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-15 16:14 [RFC] Adding PM support to thermal driver Mason
2016-06-15 21:51 ` Kevin Hilman
2016-06-17 11:11   ` Mason [this message]

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