linux-kernel - Re: [PATCH v7 1/3] dt-bindings: mtd: Add Loongson-1 NAND Controller

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Date: Sat, 18 May 2024 16:01:01 +0800
From: Keguang Zhang <keguang.zhang@...il.com>
To: Miquel Raynal <miquel.raynal@...tlin.com>
Cc: Keguang Zhang via B4 Relay <devnull+keguang.zhang.gmail.com@...nel.org>, 
	Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-mips@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v7 1/3] dt-bindings: mtd: Add Loongson-1 NAND Controller

On Mon, May 6, 2024 at 3:14 PM Miquel Raynal <miquel.raynal@...tlincom> wrote:
>
> Hello,
>
> devnull+keguang.zhang.gmail.com@...nel.org wrote on Tue, 30 Apr 2024
> 19:11:10 +0800:
>
> > From: Keguang Zhang <keguang.zhang@...il.com>
> >
> > Add devicetree binding document for Loongson-1 NAND Controller.
> >
> > Signed-off-by: Keguang Zhang <keguang.zhang@...il.com>
> > ---
> > Changes in v7:
> > - rename the file to loongson,ls1b-nfc.yaml
> >
> > Changes in v6:
> > - A newly added patch
> > ---
> >  .../devicetree/bindings/mtd/loongson,ls1b-nfc.yaml | 66 ++++++++++++++++++++++
> >  1 file changed, 66 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/mtd/loongson,ls1b-nfc.yaml b/Documentation/devicetree/bindings/mtd/loongson,ls1b-nfc.yaml
> > new file mode 100644
> > index 000000000000..a69f22b9fd9e
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mtd/loongson,ls1b-nfc.yaml
> > @@ -0,0 +1,66 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/mtd/loongson,ls1b-nfc.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Loongson-1 NAND Controller
> > +
> > +maintainers:
> > +  - Keguang Zhang <keguang.zhang@...il.com>
> > +
> > +allOf:
> > +  - $ref: nand-controller.yaml
> > +
> > +properties:
> > +  compatible:
> > +    oneOf:
> > +      - const: loongson,ls1b-nfc
>
> What is the rationale behind this choice? Seems like the b variant has
> two possible implementations and should always be preceded by a more
> specific compatible.
>
> As there is currently no description of this controller upstream, I
> would not care too much about any out-of-tree description and directly
> go for a clean description.
>
Excuse me, should I add a description for this property?

> > +      - items:
> > +          - enum:
> > +              - loongson,ls1a-nfc
> > +              - loongson,ls1c-nfc
> > +          - const: loongson,ls1b-nfc
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  dmas:
> > +    maxItems: 1
> > +
> > +  dma-names:
> > +    const: rxtx
> > +
> > +patternProperties:
> > +  "^nand@[0-3]$":
> > +    type: object
> > +    $ref: raw-nand-chip.yaml
> > +
> > +    unevaluatedProperties: false
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - dmas
> > +  - dma-names
>
> Should DMA props be required?
>
Yes. This NAND controller only works with DMA, which means the DMA is necessary.

> > +
> > +unevaluatedProperties: false
> > +
> > +examples:
> > +  - |
> > +    nand-controller@...78000 {
> > +        compatible = "loongson,ls1b-nfc";
> > +        reg = <0x1fe78000 0x40>;
> > +
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        dmas = <&dma 0>;
> > +        dma-names = "rxtx";
>
> There is a preferred spacing for DT nodes, see:
> https://docs.kernel.org/devicetree/bindings/dts-coding-style.html
>
Sorry. I don't get the meaning of preferred spacing.
https://docs.kernel.org/devicetree/bindings/writing-schema.html says
"For DTS examples in the schema, preferred is four-space indentation."
Then I used four-space indentation.

> > +
> > +        nand@0 {
> > +            reg = <0>;
> > +            nand-use-soft-ecc-engine;
> > +            nand-ecc-algo = "hamming";
>
> These two properties are not needed. Unless there is no hardware ECC
> capability on this controller and in this case you need to ensure the
> properties are present in the schema.

Exactly. This NAND controller doesn't support hardware ECC.
'nand-use-soft-ecc-engine' and 'nand-ecc-algo' are present in nand-chip.yaml.
Is there anything else I should do?

Thanks for your view!
>
> > +        };
> > +    };
> >
>
>
> Thanks,
> Miquèl



-- 
Best regards,

Keguang Zhang