[2/7] Documentation: devicetree: bindings: Add RZ/A1 pinctrl binding documentation

Add device tree bindings documentation for Renesas RZ/A1 gpio and pin
controller.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
---
 .../bindings/pinctrl/renesas,rza1-pinctrl.txt      | 114 +++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pinctrl/renesas,rza1-pinctrl.txt

On Mon, Feb 20, 2017 at 06:13:03PM +0100, Jacopo Mondi wrote:
> Add device tree bindings documentation for Renesas RZ/A1 gpio and pin
> controller.

Make the subject prefix: dt-bindings: pinctrl: ...

> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> ---
>  .../bindings/pinctrl/renesas,rza1-pinctrl.txt      | 114 +++++++++++++++++++++
>  1 file changed, 114 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pinctrl/renesas,rza1-pinctrl.txt
> 
> diff --git a/Documentation/devicetree/bindings/pinctrl/renesas,rza1-pinctrl.txt b/Documentation/devicetree/bindings/pinctrl/renesas,rza1-pinctrl.txt
> new file mode 100644
> index 0000000..1136146
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pinctrl/renesas,rza1-pinctrl.txt
> @@ -0,0 +1,114 @@
> +Renesas RZ/A1 combined Pin and GPIO controller
> +
> +Renesas SoCs of RZ/A1 family feature a combined Pin and GPIO controller
> +hardware controller, named "Ports" in the hardware reference manual.
> +Pin multiplexing and GPIO configuration is performed on a per-pin base

s/base/basis/

> +writing configuration values to per-port register sets.
> +Each "port" features up to 16 pins, each of them configurable for GPIO
> +function (port mode) or in alternate function mode.
> +Up to 8 different alternate function modes exist for each single pin.
> +
> +Pin controller node
> +-------------------
> +
> +Required properties:
> +  - compatible
> +    this shall be "renesas,r7s72100-ports".
> +
> +  - #pinctrl-cells
> +    as defined by pinctrl-bindings.txt, this is the number
> +    of cells (in addition to pin index) required to configure a single pin.
> +    Shall be set to 1.
> +
> +  - reg
> +    address base and length of the memory area where pin controller
> +    hardware is mapped to.
> +
> +Example:
> +Pin controller node for RZ/A1H SoC (r7s72100)
> +
> +pinctrl: pinctrl@fcfe3000 {
> +	compatible = "renesas,r7s72100-ports";
> +
> +	#pinctrl-cells = <1>;
> +
> +	reg = <0xfcfe3000 0x4248>;
> +};
> +
> +Sub-nodes
> +---------
> +
> +The child nodes of the pin controller node describe a pin multiplexing
> +function or a gpio controller alternatively.
> +
> +- Pin multiplexing sub-nodes:
> +  A pin multiplexing sub-node describes how to configure a set of
> +  (or a single) pin in some desired alternate function mode.
> +  A single sub-node may define several pin configurations groups.
> +
> +  Required properties:
> +    - renesas,pins
> +      describes an array of pin multiplexing configurations.
> +      When a pin has to be configured in alternate function mode, use this
> +      property to identify the pin by its global index, and provide its
> +      alternate function configuration description along with it.
> +      When multiple pins are required to be configured as part of the same
> +      alternate function (odds are single-pin alternate functions exist) they
> +      shall be specified as members of the same argument list of a single
> +      "renesas-pins" property.
> +      Helper macros to ease calculating the pin index from its position
> +      (port where it sits on and pin offset), and alternate function
> +      configuration options are provided in pin controller header file at:
> +      include/dt-bindings/pinctrl/r7s72100-pinctrl.h
> +
> +  Example:
> +  A serial communication interface with a TX output pin and a RX input pin.
> +  The RX pin requires input capabilities.
> +
> +  &pinctrl {
> +	scif2_pins: serial2 {
> +		renesas,pins = <PIN(3, 0) 6>,
> +			       <PIN(3, 2) (4 | INPUT_EN)>;
> +	};
> +  }
> +
> +  Pin #0 on port #3 is configured in alternate function #6.
> +  Pin #2 on port #3 is configured in alternate function #4 with input enabled.
> +
> +- GPIO controller sub-nodes:
> +  Each port of r7s72100 pin controller hardware is itself a gpio controller.
> +  Different SoCs have different number of available pins per port, but
> +  generally speaking, each of them can be configured in GPIO ("port") mode
> +  on this hardware.
> +  Describe gpio-controllers using sub-nodes with the following properties.
> +
> +  Required properties:
> +    - gpio-controller
> +      empty property as defined by gpio bindings documentation.
> +    - #gpio-cells
> +      number of cells required to identify and configure a GPIO.
> +      Shall be 2.
> +    - gpio-ranges
> +      Describes a gpio controller specifying its specific pin base, the pin
> +      base in the global pin numbering space, and the number of controlled
> +      pins, as defined by gpio bindings documentation. Refer to this file
> +      for a more detailed description.
> +
> +  Example:
> +  A gpio controller node, controlling 16 pins indexed starting from 0.
> +  The gpio controller base in the global pin indexing space is pin 48, thus
> +  pins [0 - 15] on this controller map to pins [48 - 63] in the global pin
> +  indexing space.
> +
> +  port3: gpio@3 {

Why can't this just be in the parent node?

3 is not valid without a reg prop.

> +	gpio-controller;
> +	#gpio-cells = <2>;
> +	gpio-ranges = <&pinctrl 0 48 16>;
> +  };
> +
> +  A device node willing to use pins controlled by this gpio controller, shall
> +  refer to it as follows:
> +
> +  led1 {
> +	gpios = <&port3 10 GPIO_ACTIVE_LOW>;
> +  };
> -- 
> 2.7.4
> 
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