linux-kernel - Re: [PATCH v4 4/4] ARM: mvebu: Armada 385 GP: Add regulators to the SATA port

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Date:	Sun, 18 Jan 2015 16:29:02 +0100
From:	Hans de Goede <hdegoede@...hat.com>
To:	Mark Brown <broonie@...nel.org>
CC:	Gregory CLEMENT <gregory.clement@...e-electrons.com>,
	Tejun Heo <tj@...nel.org>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Antoine Ténart 
	<antoine.tenart@...e-electrons.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	Jason Cooper <jason@...edaemon.net>,
	Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	linux-arm-kernel@...ts.infradead.org,
	Lior Amsalem <alior@...vell.com>,
	Tawfik Bayouk <tawfik@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Mark Rutland <mark.rutland@....com>, devicetree@...r.kernel.org
Subject: Re: [PATCH v4 4/4] ARM: mvebu: Armada 385 GP: Add regulators to the
 SATA port

Hi,

On 18-01-15 13:35, Mark Brown wrote:
> On Sat, Jan 17, 2015 at 03:28:39PM +0100, Hans de Goede wrote:
>> On 17-01-15 14:14, Mark Brown wrote:
>
>>> Following your argument to the logical conclusion means we can never
>>> turn any regualtor off - we always have the risk that there's another
>>> shared user which is going to get a power bounce if we power down.  More
>>> directly we'll also get people complaining that we're burning power
>>> pointlessly on their systems for devices they've not even got drivers
>>> enabled for.  This powering down is something there's been user demand
>>> for.
>
>> Right, note I'm only advocating to not turn off regulators marked as
>> regulator-boot-on. I would expect any regulator to have such a
>> marking to have at least one user with an actual driver. If people decide
>> to not build that driver, and then complain we can simply tell them to
>> build the driver ...
>
> Right, but that's not what regulator-boot-on actually means (and I'm not
> sure why you would think it would TBH)

Well, the meaning of regulator-boot-on is not clearly defined really, to
begin we need with fixing that, currently all the bindings file says is:

- regulator-boot-on: bootloader/firmware enabled regulator

One could easily argue that the bootloader likely has a good reason to turn
the regulator on, and that unless there is a specific driver which claims
the regulator and thus knows what to do with it it is best left alone ...

> so this will disrupt existing
> users who are expecting the current behaviour.  We could try adding a
> new property but it doesn't feel very idiomatic for DT which isn't very
> nice.
>
> Telling people not to build the driver doesn't in general work any
> better than telling them to build it in I fear, it seems like it's
> essentially just shuffling things around so people have to change their
> kernel config in a different way to avoid issues.

Regards,

Hans

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