linux-kernel - Re: [PATCH] regulator: read low power states configuration from device tree

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Message-ID: <20130726162355.GR9858@sirena.org.uk>
Date:	Fri, 26 Jul 2013 17:23:55 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Vincent Palatin <vpalatin@...omium.org>
Cc:	Grant Likely <grant.likely@...aro.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Olof Johansson <olofj@...omium.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH] regulator: read low power states configuration from
 device tree

On Fri, Jul 26, 2013 at 09:06:56AM -0700, Vincent Palatin wrote:

> > The reason this isn't in device tree at the minute is that suspend to
> > disk and suspend to RAM are somewhat Linux specific concepts and the
> > whole thing gets more and more dynamic as time moves forwards with the
> > suspend state for practical systems depending on the instantaneous
> > device state prior to entering suspend and the bits that are fixed often
> > involving sequencing elements and so on which get fixed in hardware
> > and/or bootloader.  Do you have practical systems where this is needed?

> Yes, on a Chromebook machine, an internal USB device power rail is
> connected to one of the FET of a TPS65090,
> the device is leaking power in suspend-to-RAM, it would be nice to cut
> the FET during suspend.

So this isn't powered off through a combination of the normal suspend
process and strap/bootloader configuration of the PMIC?

> you mean declaring an optional (string) property  such as :
>  regulator-suspend-mem-state
>  which can take the value "enabled" or "disabled"

I'd probably go with an optional boolean property but yes.  Suspend to
disk is relatively clear but I'm rather nervous about suspend to RAM
here.

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