linux-kernel - Re: [Patch v4 02/10] dt-bindings: dma: Add lpc32xx DMA mux binding

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Date: Fri, 21 Jun 2024 08:17:09 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Piotr Wojtaszczyk <piotr.wojtaszczyk@...esys.com>,
 Vinod Koul <vkoul@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, "J.M.B. Downing" <jonathan.downing@...tel.com>,
 Vladimir Zapolskiy <vz@...ia.com>, Liam Girdwood <lgirdwood@...il.com>,
 Mark Brown <broonie@...nel.org>, Russell King <linux@...linux.org.uk>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Andi Shyti <andi.shyti@...nel.org>,
 Miquel Raynal <miquel.raynal@...tlin.com>,
 Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>,
 Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
 Yangtao Li <frank.li@...o.com>, Arnd Bergmann <arnd@...db.de>,
 Li Zetao <lizetao1@...wei.com>, Michael Ellerman <mpe@...erman.id.au>,
 Chancel Liu <chancel.liu@....com>, dmaengine@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, alsa-devel@...a-project.org,
 linuxppc-dev@...ts.ozlabs.org, linux-sound@...r.kernel.org,
 linux-clk@...r.kernel.org, linux-i2c@...r.kernel.org,
 linux-mtd@...ts.infradead.org
Cc: Markus Elfring <Markus.Elfring@....de>
Subject: Re: [Patch v4 02/10] dt-bindings: dma: Add lpc32xx DMA mux binding

On 20/06/2024 19:56, Piotr Wojtaszczyk wrote:
> LPC32XX SoCs use pl080 dma controller which have few request signals
> multiplexed between peripherals. This binding describes how devices can
> use the multiplexed request signals.
> 
> Signed-off-by: Piotr Wojtaszczyk <piotr.wojtaszczyk@...esys.com>

> +
> +properties:
> +  "#dma-cells":
> +    const: 3
> +    description: |
> +      First two cells same as for device pointed in dma-masters.
> +      Third cell represents mux value for the request.
> +
> +  compatible:
> +    const: nxp,lpc3220-dmamux

Please put compatible first in the list of properties (and follow the
same order in "required"). It's the most important piece, so we want it
to be the first to see. It also follows the convention of DTS, where
compatible is expected to be first.

> +
> +  dma-masters:
> +    description: phandle to a dma node compatible with arm,pl080

maxItems: 1

> +
> +  reg:
> +    maxItems: 1

Keep reg after compatible.

> +
> +required:
> +  - compatible
> +  - reg
> +  - dma-masters
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    syscon@...04000 {
> +      compatible = "nxp,lpc3220-creg", "syscon", "simple-mfd";
> +      reg = <0x40004000 0x114>;
> +      ranges = <0 0x40004000 0x114>;
> +      #address-cells = <1>;
> +      #size-cells = <1>;

Drop the node above (you will see Rob's warning). Alternatively, this
schema could skip the example and the nxp,lpc3220-creg could have one
complete example for entire device with children.

> +
> +      dma-router@7c {
> +        compatible = "nxp,lpc3220-dmamux";
> +        reg = <0x7c 0x8>;
> +        #dma-cells = <3>;
> +        dma-masters = <&dma>;
> +      };
> +    };
> +
> +...
> diff --git a/MAINTAINERS b/MAINTAINERS
> index aacccb376c28..f7adf9f66dfa 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2396,6 +2396,15 @@ F:	drivers/usb/host/ohci-nxp.c
>  F:	drivers/watchdog/pnx4008_wdt.c
>  N:	lpc32xx
>  
> +ARM/LPC32XX DMAMUX SUPPORT

This should be just "LPC32XX DMAMUX SUPPORT"

> +M:	J.M.B. Downing <jonathan.downing@...tel.com>
> +M:	Piotr Wojtaszczyk <piotr.wojtaszczyk@...esys.com>
> +R:	Vladimir Zapolskiy <vz@...ia.com>
> +L:	linux-arm-kernel@...ts.infradead.org (moderated for non-subscribers)
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/dma/nxp,lpc3220-dmamux.yaml
> +N:	lpc32xx

I think this entry is only foor DMAMUX so the last "N:" is not appropriate.

You are welcomed to help maintaining the platform. Add yourself to
appropriate place of LPC32xx ARM.

Best regards,
Krzysztof