linux-kernel - Re: [PATCH v3 2/3] spi: dt-bindings: atmel,at91rm9200-spi: Add support for optional 'spi

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Message-ID: <20250805180044.GA2012043-robh@kernel.org>
Date: Tue, 5 Aug 2025 13:00:44 -0500
From: Rob Herring <robh@...nel.org>
To: Manikandan Muralidharan <manikandan.m@...rochip.com>
Cc: broonie@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	nicolas.ferre@...rochip.com, alexandre.belloni@...tlin.com,
	claudiu.beznea@...on.dev, ryan.wanner@...rochip.com,
	tudor.ambarus@...aro.org, linux-spi@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] spi: dt-bindings: atmel,at91rm9200-spi: Add
 support for optional 'spi_gclk' clock

On Tue, Aug 05, 2025 at 03:55:09PM +0530, Manikandan Muralidharan wrote:
> The Atmel SPI controller supports both the peripheral clock and the
> Generic Clock (GCLK) as sources for SPCK generation. On platforms like
> the SAM9X7 SoC, the peripheral clock can reach frequencies up to
> 266 MHz, which may exceed the maximum value supported by the Serial
> Clock Baud Rate (SCBR) divider, leading to SPI transfer failures. In such
> cases, the GCLK can be used as an alternative source for SPCK generation"
> 
> This patch updates the Atmel SPI DT binding to support an optional
> programmable SPI generic clock, specified as 'spi_gclk', in addition to
> the required 'spi_clk'.
> 
> Signed-off-by: Manikandan Muralidharan <manikandan.m@...rochip.com>
> ---
>  .../devicetree/bindings/spi/atmel,at91rm9200-spi.yaml | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/spi/atmel,at91rm9200-spi.yaml b/Documentation/devicetree/bindings/spi/atmel,at91rm9200-spi.yaml
> index d29772994cf5..11885d0cc209 100644
> --- a/Documentation/devicetree/bindings/spi/atmel,at91rm9200-spi.yaml
> +++ b/Documentation/devicetree/bindings/spi/atmel,at91rm9200-spi.yaml
> @@ -31,11 +31,16 @@ properties:
>      maxItems: 1
>  
>    clock-names:
> -    contains:
> -      const: spi_clk
> +    items:
> +      - const: spi_clk
> +      - const: spi_gclk

Well, "spi_clk" was a terrible name as it is completely redundant as 
this is the "spi" block and everything in the list is a "clk". So don't 
continue it and just do "gclk".

> +    minItems: 1
>  
>    clocks:
> -    maxItems: 1
> +    items:
> +      - description: Peripheral Bus clock
> +      - description: Programmable Generic clock
> +    minItems: 1
>  
>    dmas:
>      items:
> -- 
> 2.25.1
>