linux-kernel - Re: [PATCH v2 4/4] dt-bindings: aspeed: Add eSPI controller

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Date: Tue, 19 Mar 2024 10:56:39 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Manojkiran Eda <manojkiran.eda@...il.com>, patrick.rudolph@...ements.com,
 chiawei_wang@...eedtech.com, ryan_chen@...eedtech.com,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-aspeed@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
 linux-mtd@...ts.infradead.org
Cc: robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
 conor+dt@...nel.org, joel@....id.au, andrew@...econstruct.com.au,
 miquel.raynal@...tlin.com, richard@....at, vigneshr@...com,
 jk@...econstruct.com.au, openbmc@...ts.ozlabs.org
Subject: Re: [PATCH v2 4/4] dt-bindings: aspeed: Add eSPI controller

On 19/03/2024 10:34, Manojkiran Eda wrote:
> This commit adds the device tree bindings for aspeed eSPI
> controller.
> 
> Although aspeed eSPI hardware supports 4 different channels,
> this commit only adds the support for flash channel, the
> bindings for other channels could be upstreamed when the driver
> support for those are added.
> 
> Signed-off-by: Manojkiran Eda <manojkiran.eda@...il.com>
> ---
>  .../bindings/soc/aspeed/aspeed,espi.yaml      | 94 +++++++++++++++++++
>  1 file changed, 94 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/soc/aspeed/aspeed,espi.yaml
> 
> diff --git a/Documentation/devicetree/bindings/soc/aspeed/aspeed,espi.yaml b/Documentation/devicetree/bindings/soc/aspeed/aspeed,espi.yaml
> new file mode 100644
> index 000000000000..3d3ad528e3b3
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/soc/aspeed/aspeed,espi.yaml

Why Rob's comments got ignored?

This is not a soc component.

> @@ -0,0 +1,94 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +# # Copyright (c) 2024 IBM Corporation.
> +# # Copyright (c) 2021 Aspeed Technology Inc.
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/soc/aspeed/aspeed,espi.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Aspeed eSPI Controller
> +
> +maintainers:
> +  - Manojkiran Eda <manojkiran.eda@...il.com>
> +  - Patrick Rudolph <patrick.rudolph@...ements.com>
> +  - Chia-Wei Wang <chiawei_wang@...eedtech.com>
> +  - Ryan Chen <ryan_chen@...eedtech.com>
> +
> +description:
> +  Aspeed eSPI controller implements a device side eSPI endpoint device
> +  supporting the flash channel.

Explain what is eSPI.

> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +          - aspeed,ast2500-espi
> +          - aspeed,ast2600-espi
> +      - const: simple-mfd


That's not simple-mfd. You have driver for this. Drop.

> +      - const: syscon

That's not syscon. Why do you have ranges then? Where is any explanation
of hardware which would justify such combination?

> +
> +  reg:
> +    maxItems: 1
> +
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 1
> +
> +  ranges: true
> +
> +patternProperties:
> +  "^espi-ctrl@[0-9a-f]+$":
> +    type: object
> +
> +    description: Controls the flash channel of eSPI hardware

That explains nothing. Unless you wanted to use here MTD bindings.

This binding did not improve much. I don't understand why this is not
SPI (nothing in commit msg, nothing in description), what is eSPI, why
do you need child device, what are other children (commit msg is quite
vague here). Why there is no MTD bindings here?

All this looks like crafted for your driver, instead of using existing
DT bindings like SPI or MTD/NAND. This is a strong no-go.

> +
> +    properties:
> +      compatible:
> +        items:

No items, just use enum.

> +          - enum:
> +              - aspeed,ast2500-espi-ctrl
> +              - aspeed,ast2600-espi-ctrl
> +
> +      interrupts:
> +        maxItems: 1
> +
> +      clocks:
> +        maxItems: 1
> +
> +    required:
> +      - compatible
> +      - interrupts
> +      - clocks
> +
> +required:
> +  - compatible
> +  - reg
> +  - "#address-cells"
> +  - "#size-cells"
> +  - ranges
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +    #include <dt-bindings/clock/ast2600-clock.h>
> +
> +    espi: espi@...ee000 {
> +        compatible = "aspeed,ast2600-espi", "simple-mfd", "syscon";
> +        reg = <0x1e6ee000 0x1000>;
> +
> +        #address-cells = <1>;
> +        #size-cells = <1>;
> +        ranges = <0x0 0x1e6ee000 0x1000>;
> +
> +        espi_ctrl: espi-ctrl@0 {
> +            compatible = "aspeed,ast2600-espi-ctrl";
> +            reg = <0x0 0x800>,<0x0 0x4000000>;

Fix your style in DTS. There is always a space after ','.

> +            reg-names = "espi_ctrl","espi_flash";
> +            interrupts = <GIC_SPI 42 IRQ_TYPE_LEVEL_HIGH>;
> +            clocks = <&syscon ASPEED_CLK_GATE_ESPICLK>;
> +        };
> +    };

Best regards,
Krzysztof