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

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Message-ID: <CAP_ceTyH3Yfw5ruSWfaDz_e=vrgkS6FT8PV1XgcCAwxLroHm1g@mail.gmail.com>
Date:	Fri, 26 Jul 2013 09:06:56 -0700
From:	Vincent Palatin <vpalatin@...omium.org>
To:	Mark Brown <broonie@...nel.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 Thu, Jul 25, 2013 at 1:03 PM, Mark Brown <broonie@...nel.org> wrote:
> On Thu, Jul 25, 2013 at 12:42:00PM -0700, Vincent Palatin wrote:
>
>> +- regulator-suspend-disk-microvolt: voltage applied when entering S2D
>> +- regulator-suspend-disk-disabled: turn off when entering S2D
>> +- regulator-suspend-mem-microvolt: voltage applied when entering S2M
>> +- regulator-suspend-mem-disabled: turn off when entering S2M
>> +- regulator-suspend-standby-microvolt: voltage applied when entering standby
>> +- regulator-suspend-standby-disabled: turn off when entering standby
>
> 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.

> It's also not clear to me hat the -disabled properties make sense; if we
> have properties for the state when enabled I'd expect them to allow
> things to be marked as enabled or disabled (with don't touch as the
> default).

you mean declaring an optional (string) property  such as :
 regulator-suspend-mem-state
 which can take the value "enabled" or "disabled"
e.g.
power-regulator {
     compatible = "ti,tps65090";
     reg = <0x48>;
     voltage-regulators {
          VFET4 {
                    regulator-name = "usb_leaker";
                    regulator-suspend-mem-state = "disabled";
          };
    };
};
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