RE: [PATCH 3/7] dt-bindings: spi: dw-apb-ssi: Convert bindings to json-schema

["Wan Mohamad, Wan Ahmad Zainie" <wan.ahmad.zainie.wan.mohamad@xxxxxxxxx>]

> -----Original Message-----
> From: Rob Herring <robh@xxxxxxxxxx>
> Sent: Tuesday, March 31, 2020 12:55 AM
> To: Wan Mohamad, Wan Ahmad Zainie
> <wan.ahmad.zainie.wan.mohamad@xxxxxxxxx>
> Cc: broonie@xxxxxxxxxx; mark.rutland@xxxxxxx; linux-spi@xxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH 3/7] dt-bindings: spi: dw-apb-ssi: Convert bindings to
> json-schema
> 
> On Thu, Mar 12, 2020 at 07:31:25PM +0800, Wan Ahmad Zainie wrote:
> > Convert the Synopsis DesignWare dw-apb-ssi binding to DT schema format
> > using json-schema.
> >
> > Suggested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> > Signed-off-by: Wan Ahmad Zainie
> > <wan.ahmad.zainie.wan.mohamad@xxxxxxxxx>
> > ---
> >  .../bindings/spi/snps,dw-apb-ssi.txt          |  41 -------
> >  .../bindings/spi/snps,dw-apb-ssi.yaml         | 102 ++++++++++++++++++
> >  2 files changed, 102 insertions(+), 41 deletions(-)  delete mode
> > 100644 Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.txt
> >  create mode 100644
> > Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.txt
> > b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.txt
> > deleted file mode 100644
> > index 3ed08ee9feba..000000000000
> > --- a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.txt
> > +++ /dev/null
> > @@ -1,41 +0,0 @@
> > -Synopsys DesignWare AMBA 2.0 Synchronous Serial Interface.
> > -
> > -Required properties:
> > -- compatible : "snps,dw-apb-ssi" or "mscc,<soc>-spi", where soc is
> > "ocelot" or
> > -  "jaguar2", or "amazon,alpine-dw-apb-ssi"
> > -- reg : The register base for the controller. For "mscc,<soc>-spi", a
> > second
> > -  register set is required (named ICPU_CFG:SPI_MST)
> > -- interrupts : One interrupt, used by the controller.
> > -- #address-cells : <1>, as required by generic SPI binding.
> > -- #size-cells : <0>, also as required by generic SPI binding.
> > -- clocks : phandles for the clocks, see the description of clock-names
> below.
> > -   The phandle for the "ssi_clk" is required. The phandle for the "pclk" clock
> > -   is optional. If a single clock is specified but no clock-name, it is the
> > -   "ssi_clk" clock. If both clocks are listed, the "ssi_clk" must be first.
> > -
> > -Optional properties:
> > -- clock-names : Contains the names of the clocks:
> > -    "ssi_clk", for the core clock used to generate the external SPI clock.
> > -    "pclk", the interface clock, required for register access. If a clock domain
> > -     used to enable this clock then it should be named "pclk_clkdomain".
> > -- cs-gpios : Specifies the gpio pins to be used for chipselects.
> > -- num-cs : The number of chipselects. If omitted, this will default to 4.
> > -- reg-io-width : The I/O register width (in bytes) implemented by
> > this
> > -  device.  Supported values are 2 or 4 (the default).
> > -
> > -Child nodes as per the generic SPI binding.
> > -
> > -Example:
> > -
> > -	spi@fff00000 {
> > -		compatible = "snps,dw-apb-ssi";
> > -		reg = <0xfff00000 0x1000>;
> > -		interrupts = <0 154 4>;
> > -		#address-cells = <1>;
> > -		#size-cells = <0>;
> > -		clocks = <&spi_m_clk>;
> > -		num-cs = <2>;
> > -		cs-gpios = <&gpio0 13 0>,
> > -			   <&gpio0 14 0>;
> > -	};
> > -
> > diff --git
> > a/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> > b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> > new file mode 100644
> > index 000000000000..57a789f5d9f3
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/spi/snps,dw-apb-ssi.yaml
> > @@ -0,0 +1,102 @@
> > +# SPDX-License-Identifier: GPL-2.0-only %YAML 1.2
> > +---
> > +$id: "http://devicetree.org/schemas/spi/snps,dw-apb-ssi.yaml#";
> > +$schema: "http://devicetree.org/meta-schemas/core.yaml#";
> > +
> > +title: Synopsys DesignWare AMBA 2.0 Synchronous Serial Interface
> > +
> > +maintainers:
> > +  - Mark Brown <broonie@xxxxxxxxxx>
> 
> Should be owner for this h/w, not who takes patches.

I will ask internally, who is the current owner.

> 
> > +
> > +allOf:
> > +  - $ref: spi-controller.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    oneOf:
> > +      - items:
> > +          - enum:
> > +              - mscc,ocelot-spi
> > +              - mscc,jaguar2-spi
> > +      - items:
> > +          - const: amazon,alpine-dw-apb-ssi
> > +      - items:
> > +          - const: snps,dw-apb-ssi
> 
> This can all be a single 'enum'. You only need 'oneOf' if there are a different
> number of compatible entries.
> 
> > +
> > +  reg:
> > +    minItems: 1
> > +    maxItems: 2
> > +    oneOf:
> > +      - items:
> > +          - description: The register base for the controller.
> > +      - items:
> > +          - description: The register base for the controller.
> > +          - description: For "mscc,<soc>-spi", a second register set is
> > +                         required (named ICPU_CFG:SPI_MST)
> 
> No need for the oneOf. The 2nd case is a superset of the 1st.
> 
> > +
> > +  interrupts:
> > +    maxItems: 1
> > +    description: One interrupt, used by the controller.
> 
> Can drop description. Not specific to this h/w.
> 
> > +
> > +  '#address-cells':
> > +    const: 1
> > +
> > +  '#size-cells':
> > +    const: 0
> 
> Drop these 2. Covered by spi-controller.yaml.
> 
> > +
> > +  clocks:
> > +    minItems: 1
> > +    maxItems: 2
> > +    description: |
> > +      phandles for the clocks, see the description of clock-names below.
> > +      The phandle for the "ssi_clk" is required. The phandle for the "pclk"
> > +      clock is optional. If a single clock is specified but no clock-name,
> > +      it is the "ssi_clk" clock. If both clocks are listed, the "ssi_clk"
> > +      must be first.
> 
> Rework like:
> 
> items:
>   - description: ...
>   - description: ...
> 
> > +
> > +  clock-names:
> > +    items:
> > +      - const: ssi_clk
> > +      - const: pclk
> > +    description: |
> > +      Contains the names of the clocks.
> > +      "ssi_clk", for the core clock used to generate the external SPI clock.
> > +      "pclk", the interface clock, required for register access.
> 
> No need to repeat what's in clocks.
> 
> > +      If a clock domain used to enable this clock then it should be
> > +      named "pclk_clkdomain".
> 
> Should be a constraint:
> 
> enum: [pclk, pclk_clkdomain]
> 
> But really, it probably should be dropped. I don't understand what the
> sentence is supposed to mean.

I checked against source code, and no code in drivers/spi/ is using pclk_clkdomain,
so it is safe to remove. 

> 
> > +
> > +  cs-gpios:
> > +    description: Specifies the gpio pins to be used for chipselects.
> 
> Can drop, covered by spi-controller.yaml.
> 
> > +
> > +  num-cs:
> > +    default: 4
> > +    description: The number of chipselects. If omitted, this will default to 4.
> 
> Constraints?

I believe this is not a constraint.
Native chip select for this hardware is usually 4. We can have additional chip select
using GPIOs.

> 
> > +
> > +  reg-io-width:
> > +    default: 4
> > +    description: |
> > +      The I/O register width (in bytes) implemented by this device.
> > +      Supported values are 2 or 4 (the default).
> 
> 2 or 4?, sounds like constraints.

Yes, it is either 2 or 4 only.

I will fix this and all your comments that I haven't reply above.
Thanks for the review and comment.

> 
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - interrupts
> > +  - '#address-cells'
> > +  - '#size-cells'
> > +  - clocks
> > +
> > +examples:
> > +  - |
> > +    spi@fff00000 {
> > +          compatible = "snps,dw-apb-ssi";
> > +          reg = <0xfff00000 0x1000>;
> > +          interrupts = <0 154 4>;
> > +          #address-cells = <1>;
> > +          #size-cells = <0>;
> > +          clocks = <&spi_m_clk>;
> > +          num-cs = <2>;
> > +          cs-gpios = <&gpio0 13 0>,
> > +                     <&gpio0 14 0>;
> > +    };
> > --
> > 2.17.1
> >