linux-kernel - Re: [PATCH v5 07/16] spi: dt-bindings: axi-spi-engine: add SPI offload properties

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Message-ID: <20241119165646.GA1798301-robh@kernel.org>
Date: Tue, 19 Nov 2024 10:56:46 -0600
From: Rob Herring <robh@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: Mark Brown <broonie@...nel.org>, Jonathan Cameron <jic23@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Nuno Sá <nuno.sa@...log.com>,
	Uwe Kleine-König <ukleinek@...nel.org>,
	Michael Hennerich <Michael.Hennerich@...log.com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	David Jander <david@...tonic.nl>,
	Martin Sperl <kernel@...tin.sperl.org>, linux-spi@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org, linux-pwm@...r.kernel.org
Subject: Re: [PATCH v5 07/16] spi: dt-bindings: axi-spi-engine: add SPI
 offload properties

On Fri, Nov 15, 2024 at 02:18:46PM -0600, David Lechner wrote:
> The AXI SPI Engine has support for hardware offloading capabilities.
> This includes a connection to a DMA controller for streaming RX data
> and a trigger input for starting execution of the SPI message programmed
> in the offload.
> 
> Each SPI Engine may have up to 1 offload. The spec actually says that
> it could support up to 32, so we are using an index number in the
> dma-names (e.g. offload0-rx) to allow for this possibility in the
> future.
> 
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---
> 
> v5 changes:
> * Also document offload0-tx DMA names since the hardware can support
>   that now.
> * Limit the number of offloads to 1 for now since it would require
>   significant hardware changes to actually support more than that.
> 
> v4 changes:
> * Dropped #spi-offload-cells property.
> * Changed subject line.
> 
> v3 changes:
> * Added #spi-offload-cells property.
> * Added properties for triggers and RX data stream connected to DMA.
> 
> v2 changes:
> * This is basically a new patch. It partially replaces "dt-bindings:
>   iio: offload: add binding for PWM/DMA triggered buffer".
> * The controller no longer has an offloads object node and the
>   spi-offloads property is now a standard SPI peripheral property.
> ---
>  .../bindings/spi/adi,axi-spi-engine.yaml           | 24 ++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/spi/adi,axi-spi-engine.yaml b/Documentation/devicetree/bindings/spi/adi,axi-spi-engine.yaml
> index d48faa42d025..d703b47eb498 100644
> --- a/Documentation/devicetree/bindings/spi/adi,axi-spi-engine.yaml
> +++ b/Documentation/devicetree/bindings/spi/adi,axi-spi-engine.yaml
> @@ -41,6 +41,26 @@ properties:
>        - const: s_axi_aclk
>        - const: spi_clk
>  
> +  trigger-sources:
> +    description:
> +      An array of trigger source phandles for offload instances. The index in
> +      the array corresponds to the offload instance number.

How can you have an index when you only allow 1 entry (other than 0 of 
course)?

> +    $ref: /schemas/types.yaml#/definitions/phandle-array

With my other comments implemented, this should be dropped.

> +    maxItems: 1
> +
> +  dmas:
> +    description:
> +      DMA channels connected to the input or output stream interface of an
> +      offload instance.
> +    minItems: 1
> +    maxItems: 2
> +
> +  dma-names:
> +    items:
> +      pattern: "^offload0-[tr]x$"

Do you expect an offload1 or something?

> +    minItems: 1
> +    maxItems: 2
> +
>  required:
>    - compatible
>    - reg
> @@ -59,6 +79,10 @@ examples:
>          clocks = <&clkc 15>, <&clkc 15>;
>          clock-names = "s_axi_aclk", "spi_clk";
>  
> +        trigger-sources = <&trigger_clock>;
> +        dmas = <&dma 0>;
> +        dma-names = "offload0-rx";
> +
>          #address-cells = <1>;
>          #size-cells = <0>;
>  
> 
> -- 
> 2.43.0
>