linux-kernel - Re: [PATCH 1/2] spi: renesas,rzv2m-csi: Add SPI Slave related properties

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Date:   Wed, 27 Sep 2023 09:59:05 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Fabrizio Castro <fabrizio.castro.jz@...esas.com>
Cc:     Mark Brown <broonie@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Magnus Damm <magnus.damm@...il.com>, linux-spi@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH 1/2] spi: renesas,rzv2m-csi: Add SPI Slave related properties

Hi Fabrizio,

On Tue, Sep 26, 2023 at 11:08 PM Fabrizio Castro
<fabrizio.castro.jz@...esas.com> wrote:
> The CSI IP found inside the Renesas RZ/V2M SoC can also work
> in SPI slave mode.
> When working in slave mode, the IP can make use of the SS
> (Slave Select) pin, with "low" as default active level.
> The active level of SS can be changed to "high" upon configuration.
> This patch adds two new properties, one to make use of the
> SS pin when in slave mode, and one to make the SS pin active high.
>
> Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@...esas.com>

Thanks for your patch!

> --- a/Documentation/devicetree/bindings/spi/renesas,rzv2m-csi.yaml
> +++ b/Documentation/devicetree/bindings/spi/renesas,rzv2m-csi.yaml
> @@ -39,6 +39,17 @@ properties:
>    power-domains:
>      maxItems: 1
>
> +  renesas,csi-ss:
> +    type: boolean
> +    description:
> +      Use CSI Slave Selection (SS) pin to enable transmission and reception when
> +      in slave mode.

Can't this be done in a more generic way? I had expected that the
existing SPI_NO_CS flag can be set using a property in the "slave" subnode,
but apparently there is no "spi-no-cs" property defined yet.

> +
> +  renesas,csi-ss-high:
> +    type: boolean
> +    description:
> +      The SS pin is active high (by default the SS pin is active low).

Can't you use the "spi-cs-high" property in the "slave" subnode instead?

> +
>  required:
>    - compatible
>    - reg

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds