linux-kernel - Re: [PATCHv2 3/6] power: supply: gpio-charger: add charge-current-limit feature

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Message-ID: <20200619162820.hhv5rftp4xkhwtix@earth.universe>
Date:   Fri, 19 Jun 2020 18:28:20 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Emil Velikov <emil.velikov@...labora.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        Russell King <linux@...linux.org.uk>, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCHv2 3/6] power: supply: gpio-charger: add
 charge-current-limit feature

Hi,

On Mon, Jun 15, 2020 at 11:58:44AM -0600, Rob Herring wrote:
> On Sat, Jun 06, 2020 at 12:44:00AM +0200, Sebastian Reichel wrote:
> > Add new charge-current-limit feature to gpio-charger.
> > 
> > Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.com>
> > ---
> >  .../bindings/power/supply/gpio-charger.yaml   |  31 ++++
> >  drivers/power/supply/gpio-charger.c           | 140 ++++++++++++++++++
> >  2 files changed, 171 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/power/supply/gpio-charger.yaml b/Documentation/devicetree/bindings/power/supply/gpio-charger.yaml
> > index 30eabbb14ef3..e11cfdc68a51 100644
> > --- a/Documentation/devicetree/bindings/power/supply/gpio-charger.yaml
> > +++ b/Documentation/devicetree/bindings/power/supply/gpio-charger.yaml
> > @@ -39,6 +39,25 @@ properties:
> >      maxItems: 1
> >      description: GPIO indicating the charging status
> >  
> > +  charge-current-limit-gpios:
> > +    minItems: 1
> > +    maxItems: 32
> > +    description: GPIOs used for current limiting
> > +
> > +  charge-current-limit-mapping:
> > +    description: List of touples with current in uA and a GPIO bitmap (in
> 
> s/touples/tuples/
> 
> > +      this order). The touples must be provided in descending order of the
> 
> and here.

Ack.

> > +      current limit.
> > +    $ref: /schemas/types.yaml#/definitions/uint32-matrix
> > +    items:
> > +      items:
> > +        - description:
> > +            Current limit in uA
> > +        - description:
> > +            Encoded GPIO setting. Bit 0 represents last GPIO from the
> > +            charge-current-limit-gpios property. Bit 1 second to last
> > +            GPIO and so on.
> 
> Seems a bit odd that bit N doesn't represent index N of the gpios.

I was looking at it from a graphical POV (i.e. "last" bit represents
last element):

list = <element3, element2, element1, element0>;
bits = 0b1011; // element3, 1 and 0

Basically when writing it the order is the same at the cost of list
index being reverse of bit index. But I do not really mind the order.
If people think its better the other way around I can swap it.

-- Sebastian

> > +
> >  required:
> >    - compatible
> >  
> > @@ -47,6 +66,12 @@ anyOf:
> >      - gpios
> >    - required:
> >      - charge-status-gpios
> > +  - required:
> > +    - charge-current-limit-gpios
> > +
> > +dependencies:
> > +  charge-current-limit-gpios: [ charge-current-limit-mapping ]
> > +  charge-current-limit-mapping: [ charge-current-limit-gpios ]
> >  
> >  additionalProperties: false
> >  
> > @@ -60,4 +85,10 @@ examples:
> >  
> >        gpios = <&gpd 28 GPIO_ACTIVE_LOW>;
> >        charge-status-gpios = <&gpc 27 GPIO_ACTIVE_LOW>;
> > +
> > +      charge-current-limit-gpios = <&gpioA 11 GPIO_ACTIVE_HIGH>,
> > +                                   <&gpioA 12 GPIO_ACTIVE_HIGH>;
> > +      charge-current-limit-mapping = <2500000 0x00>, // 2.5 A => both GPIOs low
> > +                                     <700000 0x01>, // 700 mA => GPIO A.12 high
> > +                                     <0 0x02>; // 0 mA => GPIO A.11 high
> >      };

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