Re: [RFC 4/4] dt-bindings: gpio: Add bindings for SCMI pinctrl based gpio

From: AKASHI Takahiro <takahiro.akashi@linaro.org>
To: Rob Herring <robh@kernel.org>
Cc: sudeep.holla@arm.com, cristian.marussi@arm.com,
	krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
	linus.walleij@linaro.org, Oleksii_Moisieiev@epam.com,
	linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org
Subject: Re: [RFC 4/4] dt-bindings: gpio: Add bindings for SCMI pinctrl based gpio
Date: Tue, 3 Oct 2023 09:41:58 +0900	[thread overview]
Message-ID: <ZRtjVnWhAK2CZaRM@octopus> (raw)
In-Reply-To: <20231002144155.GA1675188-robh@kernel.org>

Hi Rob,

On Mon, Oct 02, 2023 at 09:41:55AM -0500, Rob Herring wrote:
> On Mon, Oct 02, 2023 at 11:16:02AM +0900, AKASHI Takahiro wrote:
> > A dt binding for SCMI pinctrl based gpio driver is defined in this
> > commit. It basically conforms to generic pinctrl-gpio mapping framework.
> 
> What is "generic pinctrl-gpio mapping framework"? DT doesn't have 
> frameworks.

I meant to refer to section 2.1-2.3 in "Documentation/devicetree/bindings/gpio/gpio.txt". The semantics is implemented in drivers/gpio/gpiolib(-of).c.

> > 
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > ---
> >  .../bindings/gpio/arm,scmi-gpio.yaml          | 71 +++++++++++++++++++
> >  1 file changed, 71 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/gpio/arm,scmi-gpio.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/gpio/arm,scmi-gpio.yaml b/Documentation/devicetree/bindings/gpio/arm,scmi-gpio.yaml
> > new file mode 100644
> > index 000000000000..2601c5594567
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/gpio/arm,scmi-gpio.yaml
> > @@ -0,0 +1,71 @@
> > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/gpio/arm,scmi-gpio.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: SCMI pinctrl based generic GPIO controller
> > +
> > +maintainers:
> > +  - AKASHI Takahiro <akashi.takahiro@linaro.org>
> > +
> > +properties:
> > +  $nodename:
> > +    pattern: "^scmi_gpio(@[0-9a-f]+)$"
> 
> Not the correct name.

How not?

> > +
> > +  compatible:
> > +    const: arm,scmi-gpio-generic
> 
> What makes it generic? No such thing. Just drop '-generic'.

I will discuss this issue in following Cristian's comment.

> 
> > +
> > +  gpio-controller: true
> > +
> > +  "#gpio-cells":
> > +    const: 2
> > +
> > +  gpio-ranges: true
> > +
> > +  gpio-ranges-group-names: true
> > +
> > +patternProperties:
> > +  "^.+-hog(-[0-9]+)?$":
> > +    type: object
> > +    properties:
> > +      gpio-hog: true
> > +      gpios: true
> > +      input: true
> > +      output-high: true
> > +      output-low: true
> > +      line-name: true
> > +
> > +    required:
> > +      - gpio-hog
> > +      - gpios
> 
> You don't need all this just 'required: [ gpio-hog ]'. Then the hog 
> schema will check the rest.

Okay.

> > +
> > +    additionalProperties: false
> > +
> > +required:
> > +  - compatible
> > +  - gpio-controller
> > +  - "#gpio-cells"
> > +  - gpio-ranges
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/gpio/gpio.h>
> > +
> > +    scmi_gpio_0: scmi_gpio@0 {
> 
> gpio {
> 
> But doesn't SCMI have protocol numbers?
> 
> > +        compatible = "arm,scmi-gpio";
> > +        gpio-controller;
> > +        #gpio-cells = <2>;
> > +        gpio-ranges = <&scmi_pinctrl 0 10 5>,
> > +                      <&scmi_pinctrl 5 0 0>;
> > +        gpio-ranges-group-names = "",
> > +                                  "pinmux_gpio";
> > +    };
> > +
> > +    // Consumer:
> 
> Outside the scope of this binding. Drop this node.

Even though it's in an example?
"#gpio-cells" has a meaning in consumer side.

-Takahiro Akashi

> > +    sdhci0_pwrseq {
> > +        compatible = "mmc-pwrseq-emmc";
> > +        reset-gpios = <&scmi_gpio_0 0 GPIO_ACTIVE_LOW>;
> > +    };
> > -- 
> > 2.34.1
> > 