Re: [PATCH v4 1/6] dt-bindings: i3c: Convert controller description to yaml

[Rob Herring <robh@kernel.org>]

On Thu, Jan 14, 2021 at 06:55:53PM +0100, Miquel Raynal wrote:
> Attempting a conversion of the i3c.txt file to yaml schema with
> minimal content changes.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> ---
>  Documentation/devicetree/bindings/i3c/i3c.txt | 140 -------------
>  .../devicetree/bindings/i3c/i3c.yaml          | 186 ++++++++++++++++++
>  2 files changed, 186 insertions(+), 140 deletions(-)
>  delete mode 100644 Documentation/devicetree/bindings/i3c/i3c.txt
>  create mode 100644 Documentation/devicetree/bindings/i3c/i3c.yaml


> diff --git a/Documentation/devicetree/bindings/i3c/i3c.yaml b/Documentation/devicetree/bindings/i3c/i3c.yaml
> new file mode 100644
> index 000000000000..79df533ab094
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i3c/i3c.yaml
> @@ -0,0 +1,186 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/i3c/i3c.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: I3C bus binding
> +
> +maintainers:
> +  - Alexandre Belloni <alexandre.belloni@bootlin.com>
> +  - Miquel Raynal <miquel.raynal@bootlin.com>
> +
> +description: |
> +  I3C busses can be described with a node for the primary I3C controller device
> +  and a set of child nodes for each I2C or I3C slave on the bus. Each of them
> +  may, during the life of the bus, request mastership.
> +
> +properties:
> +  $nodename:
> +    pattern: "^i3c-master(@.*|-[0-9a-f])*$"
> +
> +  "#address-cells":
> +    const: 3
> +    description: |
> +      Each I2C device connected to the bus should be described in a subnode.
> +
> +      All I3C devices are supposed to support DAA (Dynamic Address Assignment),
> +      and are thus discoverable. So, by default, I3C devices do not have to be
> +      described in the device tree. This being said, one might want to attach
> +      extra resources to these devices, and those resources may have to be
> +      described in the device tree, which in turn means we have to describe
> +      I3C devices.
> +
> +      Another use case for describing an I3C device in the device tree is when
> +      this I3C device has a static I2C address and we want to assign it a
> +      specific I3C dynamic address before the DAA takes place (so that other
> +      devices on the bus can't take this dynamic address).
> +
> +  "#size-cells":
> +    const: 0
> +
> +  i3c-scl-hz:
> +    $ref: /schemas/types.yaml#/definitions/uint32

With a unit suffix, you don't need the type.

> +    description: |
> +      Frequency of the SCL signal used for I3C transfers. When undefined, the
> +      default value should be 12.5MHz.
> +
> +      May not be supported by all controllers.
> +
> +  i2c-scl-hz:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +      Frequency of the SCL signal used for I2C transfers. When undefined, the
> +      default should be to look at LVR (Legacy Virtual Register) values of
> +      I2C devices described in the device tree to determine the maximum I2C
> +      frequency.
> +
> +      May not be supported by all controllers.
> +
> +required:
> +  - "#address-cells"
> +  - "#size-cells"
> +
> +patternProperties:
> +  "^.*@[0-9a-f]+$":

You can drop '^.*':

"@[0-9a-f]+$"

> +    type: object
> +    description: |
> +      I2C child, should be named: <device-type>@<i2c-address>
> +
> +      All properties described in Documentation/devicetree/bindings/i2c/i2c.txt
> +      are valid here, except the reg property whose content is changed.
> +
> +    properties:
> +      compatible:
> +        description:
> +          Compatible of the I2C device.
> +
> +      reg:
> +        items:
> +          - description: |
> +              1st cell
> +              ========
> +
> +              I2C address. 10 bit addressing is not supported. Devices with
> +              10-bit address can't be properly passed through DEFSLVS command.
> +
> +              2nd cell
> +              ========
> +
> +              Should be 0.
> +
> +              3rd cell
> +              ========
> +
> +              Shall encode the I3C LVR (Legacy Virtual Register):
> +              bit[31:8]: unused/ignored
> +              bit[7:5]: I2C device index. Possible values:
> +                * 0: I2C device has a 50 ns spike filter
> +                * 1: I2C device does not have a 50 ns spike filter but supports
> +                     high frequency on SCL
> +                * 2: I2C device does not have a 50 ns spike filter and is not
> +                     tolerant to high frequencies
> +                * 3-7: reserved
> +              bit[4]: tell whether the device operates in FM (Fast Mode) or
> +                      FM+ mode:
> +                * 0: FM+ mode
> +                * 1: FM mode
> +              bit[3:0]: device type
> +                * 0-15: reserved

We can do a bit better:

reg:
  items:
    - items:  # Note: drop the '-' if we support more than 1 entry
        - description: I2C address...
          maximum: 0x7f  # Not sure this works, do we support the high 
                         # flag bits here?
        - const: 0
        - description: I3C LVR (Legacy Virtual Register)...

> +
> +    required:
> +      - compatible
> +      - reg
> +
> +  "^.*@[0-9a-f]+,[0-9a-f]+$":
> +    type: object
> +    description: |
> +      I3C child, should be named: <device-type>@<static-i2c-address>,<i3c-pid>
> +
> +    properties:
> +      reg:
> +        items:
> +          - description: |
> +              1st cell
> +              ========
> +
> +              Encodes the static I2C address. Should be 0 if the device does not
> +              have one (0 is not a valid I2C address).
> +
> +              2nd and 3rd cells
> +              =================
> +
> +              ProvisionalID (following the PID definition provided by the I3C
> +              specification).
> +
> +              Cell 2 contains the manufacturer ID left-shifted by 1. Cell 3
> +              contains the ORing of the part ID left-shifted by 16, the instance
> +              ID left-shifted by 12 and extra information.

Similar rework here.

> +
> +      assigned-address:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        minimum: 0x01
> +        maximum: 0xFF
> +        description: |
> +          Dynamic address to be assigned to this device. This property is only
> +          valid if the I3C device has a static address (first cell of the reg
> +          property != 0).
> +
> +    required:
> +      - reg
> +
> +additionalProperties: true
> +
> +examples:
> +  - |
> +    i3c-master@d040000 {
> +        compatible = "cdns,i3c-master";
> +        clocks = <&coreclock>, <&i3csysclock>;
> +        clock-names = "pclk", "sysclk";
> +        interrupts = <3 0>;
> +        reg = <0x0d040000 0x1000>;
> +        #address-cells = <3>;
> +        #size-cells = <0>;
> +        i2c-scl-hz = <100000>;
> +
> +        /* I2C device. */
> +        nunchuk: nunchuk@52 {
> +            compatible = "nintendo,nunchuk";
> +            reg = <0x52 0x0 0x10>;
> +        };
> +
> +        /* I3C device with a static I2C address. */
> +        thermal_sensor: sensor@68,39200144004 {
> +            reg = <0x68 0x392 0x144004>;
> +            assigned-address = <0xa>;
> +        };
> +
> +        /*
> +         * I3C device without a static I2C address but requiring
> +         * resources described in the DT.
> +         */
> +        sensor@0,39200154004 {
> +            reg = <0x0 0x392 0x154004>;
> +            clocks = <&clock_provider 0>;
> +        };
> +    };
> -- 
> 2.20.1
> 

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