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

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Date: Sat, 18 May 2024 12:47:32 +0200
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Keguang Zhang <keguang.zhang@...il.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

Hi,

keguang.zhang@...il.com wrote on Sat, 18 May 2024 16:01:01 +0800:

> On Mon, May 6, 2024 at 3:14 PM Miquel Raynal <miquel.raynal@...tlin.com> 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?

No, description is not needed. But you are allowing the
"loongson,ls1b-nfc" compatible alone, which I think is not relevant,
unless you convince me it is :-)

> > > +      - 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.

Ok

> 
> > > +
> > > +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.

I'm talking about the new lines (\n) between the properties.
 
> 
> > > +
> > > +        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?

Thry are in nand-chip.yaml, which means they are allowed, but I want
them mandatory:

required:
  - foo
  - bar

Thanks,
Miquèl