linux-kernel - Re: [PATCH v3 06/12] power: pwrseq: simple: Add support for regulator and generic property

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Date:	Mon, 6 Jun 2016 11:22:40 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	Rob Herring <robh@...nel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Javier Martinez Canillas <javier@....samsung.com>,
	linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
	linux-pm@...r.kernel.or, Alan Stern <stern@...land.harvard.edu>,
	linux-usb@...r.kernel.org, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Kukjin Kim <kgene@...nel.org>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v3 06/12] power: pwrseq: simple: Add support for
 regulator and generic property

On Fri, Jun 03, 2016 at 02:35:08PM +0200, Krzysztof Kozlowski wrote:
> On 06/03/2016 04:02 AM, Rob Herring wrote:
> > On Wed, Jun 01, 2016 at 10:02:15AM +0200, Krzysztof Kozlowski wrote:
> >> Some devices need real hard-reset by cutting the power.  During power
> >> sequence turn off and on the regulator, if it is provided.
> >>
> >> Additionally add support for instantiating the pwrseq-simple device on a
> >> generic property 'power-sequence'.  The device will attach itself to the
> >> node containing the property and parse the node's properties like
> >> reset-gpios, ext-supply etc.
> >>
> >> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> >> ---
> >>  .../bindings/power/pwrseq/pwrseq-simple.txt        | 29 +++++++-
> >>  drivers/power/pwrseq/pwrseq_simple.c               | 85 +++++++++++++++++++++-
> >>  2 files changed, 107 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/Documentation/devicetree/bindings/power/pwrseq/pwrseq-simple.txt b/Documentation/devicetree/bindings/power/pwrseq/pwrseq-simple.txt
> >> index ce0e76749671..a8c3f13ee83f 100644
> >> --- a/Documentation/devicetree/bindings/power/pwrseq/pwrseq-simple.txt
> >> +++ b/Documentation/devicetree/bindings/power/pwrseq/pwrseq-simple.txt
> >> @@ -1,11 +1,17 @@
> >> -* The simple MMC power sequence provider
> >> +* The simple power sequence provider
> >>  
> >> -The purpose of the simple MMC power sequence provider is to supports a set of
> >> +The purpose of the simple power sequence provider is to supports a set of
> >>  common properties between various SOC designs. It thus enables us to use the
> >>  same provider for several SOC designs.
> >>  
> >> -Required properties:
> >> -- compatible : contains "mmc-pwrseq-simple".
> >> +The driver supports two types of bindings:
> >> +1. Separate node
> >> +   Required properties:
> >> +   - compatible : contains "mmc-pwrseq-simple".
> > 
> > Please note that this is not recommended for new users.
> 
> Sure.
> 
> > 
> >> +
> >> +2. Property for any node
> >> +   Required properties:
> >> +   - power-sequence
> >>  
> >>  Optional properties:
> >>  - reset-gpios : contains a list of GPIO specifiers. The reset GPIOs are asserted
> >> @@ -16,6 +22,7 @@ Optional properties:
> >>    See ../clocks/clock-bindings.txt for details.
> >>  - clock-names : Must include the following entry:
> >>    "ext_clock" (External clock provided to the card).
> >> +- ext-supply : External regulator supply
> > 
> > What happens when there are 2 supplies?
> > 
> > I'd prefer the name not be genericish and use the real supply names. 
> > Then the power seq code should just turn on all supplies it finds. If 
> > the order or timing to turn on matters, then sorry, no generic sequence.
> 
> Understood. I'll change the code to use any supply.
> 
> As for the genericness of this approach, Sylwester Nawrocki pointed an
> old thread:
> [PATCH v6 0/4] Runtime Interpreted Power Sequences
> https://lkml.org/lkml/2012/9/12/127
> 
> How do you like that approach?
> 

Rob, I am trying to implement the dts layout you suggested (see below),
but I find it is very hard to it due to the device is still not created,
without device, it is hard to manage the resources under this device (
Eg, de-initialization for probe deferral case). So, a common driver
is suitable for this power sequence case.

&usbotg1 {
        vbus-supply = <&reg_usb_otg1_vbus>;
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_usb_otg1_id>;
        status = "okay";

        #address-cells = <1>;
        #size-cells = <0>;
        hub: genesys@1 {
                compatible = "usb5e3,608";
                reg = <1>;
                reset-gpios = <&gpio4 5 GPIO_ACTIVE_LOW>; /* hub reset pin */
                reset-duration-us = <10>;
                clocks = <&clks IMX6SX_CLK_CKO>;
        };
};

-- 

Best Regards,
Peter Chen