linux-kernel - Re: [PATCH v4 1/3] pinctrl: Add sleep related configuration

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Date:   Tue, 27 Jun 2017 16:21:33 +0800
From:   Baolin Wang <baolin.wang@...eadtrum.com>
To:     Rob Herring <robh@...nel.org>
CC:     <linus.walleij@...aro.org>, <mark.rutland@....com>,
        <linux-gpio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <broonie@...nel.org>,
        <baolin.wang@...aro.org>
Subject: Re: [PATCH v4 1/3] pinctrl: Add sleep related configuration

On 一,  6月 26, 2017 at 11:13:48上午 -0500, Rob Herring wrote:
> On Wed, Jun 21, 2017 at 07:55:37PM +0800, Baolin Wang wrote:
> > In some scenarios, we should set some pins as input/output/pullup/pulldown
> > when the specified system goes into deep sleep mode, then when the system
> > goes into deep sleep mode, these pins will be set automatically by hardware.
> > 
> > Usually we can set the "sleep" state to set sleep related config, but one SoC
> > usually has not only one system (especially for mobile SoC), some systems on
> > the SoC which did not run linux kernel, they can not select the "sleep" state
> > when they go into deep sleep mode.
> 
> The wording here is not very clear. I think what you mean is some pins 
> are not controlled by any specific driver in the OS, but need to be 
> controlled when entering sleep mode.

Yes, that is what I meaning, sorry for confusing.

> 
> > Thus we introduce some sleep related config into pinconf-generic for users to
> > configure.
> > 
> > Signed-off-by: Baolin Wang <baolin.wang@...eadtrum.com>
> > ---
> >  - Add this patch since v4.
> > ---
> >  .../bindings/pinctrl/pinctrl-bindings.txt          |   12 ++++++++++++
> >  drivers/pinctrl/pinconf-generic.c                  |   10 ++++++++++
> >  include/linux/pinctrl/pinconf-generic.h            |   14 ++++++++++++++
> >  3 files changed, 36 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
> > index bf3f7b0..e098059 100644
> > --- a/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
> > +++ b/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
> > @@ -236,6 +236,18 @@ low-power-enable	- enable low power mode
> >  low-power-disable	- disable low power mode
> >  output-low		- set the pin to output mode with low level
> >  output-high		- set the pin to output mode with high level
> > +sleep-bias-pull-up	- pull up the pin when the specified system goes into
> > +			  deep sleep mode
> > +sleep-bias-pull-down	- pull down the pin when the specified system goes into
> > +			  deep sleep mode
> > +sleep-input-enable	- enable input on pin when the specified system goes
> > +			  into deep sleep mode (no effect on output)
> > +sleep-intput-disable	- disable input on pin when the specified system goes
> > +			  into deep sleep mode (no effect on output)
> > +sleep-output-low	- set the pin to output mode with low level when the
> > +			  specified system goes into deep sleep mode
> > +sleep-output-high	- set the pin to output mode with high level when the
> > +			  specified system goes into deep sleep mode
> >  slew-rate		- set the slew rate
> 
> I don't really like having 2 ways to define pin setup and this doesn't 
> scale if I need to define 3 states. Couldn't we create pin state 
> definitions and have a pinctrl-n property within the pin controller 
> node to handle all the unhandled pins?

As LinusW also suggest we can create one "sleep" state and program them
into registers at early point (like: after probing pinctrl driver). So I
think I can introduce one called "early-sleep" state which need select it
after initializing pinctrl driver.

> 
> Rob