linux-kernel - Re: [PATCH 2/2] dt-bindings: fpga: add binding doc for ecp5-spi fpga mgr

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Date:   Fri, 15 Jul 2022 11:33:54 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Ivan Bornyakov <i.bornyakov@...rotek.ru>, mdf@...nel.org,
        hao.wu@...el.com, yilun.xu@...el.com, trix@...hat.com,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org
Cc:     linux-fpga@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, system@...rotek.ru
Subject: Re: [PATCH 2/2] dt-bindings: fpga: add binding doc for ecp5-spi fpga
 mgr

On 14/07/2022 14:26, Ivan Bornyakov wrote:
> Add Device Tree Binding doc for Lattice ECP5 FPGA manager using slave
> SPI to load .bit formatted uncompressed bitstream image.
> 
> Signed-off-by: Ivan Bornyakov <i.bornyakov@...rotek.ru>
> ---
>  .../fpga/lattice,ecp5-spi-fpga-mgr.yaml       | 71 +++++++++++++++++++
>  1 file changed, 71 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/fpga/lattice,ecp5-spi-fpga-mgr.yaml
> 
> diff --git a/Documentation/devicetree/bindings/fpga/lattice,ecp5-spi-fpga-mgr.yaml b/Documentation/devicetree/bindings/fpga/lattice,ecp5-spi-fpga-mgr.yaml
> new file mode 100644
> index 000000000000..79868f9c84e2
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/fpga/lattice,ecp5-spi-fpga-mgr.yaml
> @@ -0,0 +1,71 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/fpga/lattice,ecp5-spi-fpga-mgr.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Lattice ECP5 FPGA manager.
> +
> +maintainers:
> +  - Ivan Bornyakov <i.bornyakov@...rotek.ru>
> +
> +description:
> +  Device Tree Bindings for Lattice ECP5 FPGA Manager using slave SPI to
> +  load the uncompressed bitstream in .bit format.

s/Device Tree Bindings for//

Instead describe the hardware you are adding bindings for. What is a
"Manager"? It is so broad and unspecific... It is some dedicated
hardware to communicate with FPGA or you just called this regular FPGA
interface exposed to the CPU/SoC?

> +
> +properties:
> +  compatible:
> +    enum:
> +      - lattice,ecp5-spi-fpga-mgr

Do not encode interface name in compatible so no "spi".

> +
> +  reg:
> +    description: SPI chip select
> +    maxItems: 1
> +
> +  spi-max-frequency:
> +    maximum: 60000000

Reference spi/spi-peripheral-props.yaml in allOf

> +
> +  program-gpios:
> +    description:
> +      A GPIO line connected to PROGRAMN (active low) pin of the device.
> +      Initiates configuration sequence.
> +    maxItems: 1
> +
> +  init-gpios:
> +    description:
> +      A GPIO line connected to INITN (active low) pin of the device.
> +      Indicates the FPGA is ready to be configured.
> +    maxItems: 1
> +
> +  done-gpios:
> +    description:
> +      A GPIO line connected to DONE (active high) pin of the device.
> +      Indicates that the configuration sequence is complete.
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +  - reg
> +  - program-gpios
> +  - init-gpios
> +  - done-gpios
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +
> +    spi {
> +            #address-cells = <1>;

Wrong indentation. 4-spaces for DTS example.

> +            #size-cells = <0>;
> +
> +            fpga_mgr@0 {

No underscores in node names.

> +                    compatible = "lattice,ecp5-spi-fpga-mgr";
> +                    spi-max-frequency = <20000000>;
> +                    reg = <0>;
> +                    program-gpios = <&gpio3 4 GPIO_ACTIVE_LOW>;
> +                    init-gpios = <&gpio3 3 GPIO_ACTIVE_LOW>;
> +                    done-gpios = <&gpio3 2 GPIO_ACTIVE_HIGH>;
> +            };
> +    };


Best regards,
Krzysztof