linux-kernel - Re: [PATCH 1/2] ARM: dts: omap5-uevm: remove always_on, boot_on from smps10

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Date:	Fri, 11 Oct 2013 01:30:52 -0500
From:	Nishanth Menon <nm@...com>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	Mark Rutland <mark.rutland@....com>,
	dt list <devicetree@...r.kernel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Pawel Moll <pawel.moll@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	Tony Lindgren <tony@...mide.com>,
	Stephen Warren <swarren@...dotorg.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Benoit Cousson <bcousson@...libre.com>,
	linux-omap <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] ARM: dts: omap5-uevm: remove always_on, boot_on from smps10_out1

On Fri, Oct 11, 2013 at 1:13 AM, Kishon Vijay Abraham I <kishon@...com> wrote:
>
>> regulator-boot-on indicates that PMIC enables it by default as part of
>> OTP or some internal behavior -> Looking at the measurements done on
>> uEVM and OTP information -> regulator-boot-on should be kept here.
>
> No. Actually I don’t want PMIC to enable it by default. I want the palmas-usb
> driver to handle it.
> Enabling it by default makes palmas-usb to detect VBUS interrupt. This should
> ideally be detected only when you connect a host cable.
> Btw I didn't exactly get why you want regulator-boot-on should be kept here.

binding description states:
- regulator-boot-on: bootloader/firmware enabled regulator
Further info: include/linux/regulator/machine.h
* @boot_on: Set if the regulator is enabled when the system is initially
*           started.  If the regulator is not enabled by the hardware or
*           bootloader then it will be enabled when the constraints are
*           applied.

What that means is that it is enabled by firmware/bootloader (in our
case One Time Program {OTP} inside Palmas) when the system switches on
even before the kernel starts. and we know SMPS10 is autoenabled by
Palmas OTP configuration even before first instruction in A15
executes.

I think you misunderstand this to mean that you'd like the regulator
to be *switched on* automatically at kernel boot by regulator
framework - there is no reasoning why we'd want such a binding since
we'd expect drivers to do their job of requesting and enabling
regulators on need..

Hope this helps. Let me know if I misunderstood something here.

Regards,
Nishanth Menon
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