linux-kernel - Re: [PATCH V3 RESEND 1/2] dt-bindings: spi: tegra: Document IOMMU property for Tegra234 QSPI

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Message-ID: <20250512-observant-rental-21927c85c709@spud>
Date: Mon, 12 May 2025 17:49:29 +0100
From: Conor Dooley <conor@...nel.org>
To: Vishwaroop A <va@...dia.com>
Cc: krzk@...nel.org, broonie@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, thierry.reding@...il.com,
	jonathanh@...dia.com, skomatineni@...dia.com, ldewangan@...dia.com,
	kyarlagadda@...dia.com, smangipudi@...dia.com, bgriffis@...dia.com,
	linux-spi@...r.kernel.org, devicetree@...r.kernel.org,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 RESEND 1/2] dt-bindings: spi: tegra: Document IOMMU
 property for Tegra234 QSPI

On Fri, May 09, 2025 at 04:54:08PM +0000, Vishwaroop A wrote:
> Add the 'iommus' property to the Tegra QSPI device tree binding.
> The property is needed for Tegra234 when using the internal DMA
> controller, and is not supported on other Tegra chips, as DMA is
> handled by an external controller.
> 
> Signed-off-by: Vishwaroop A <va@...dia.com>
> ---
>  .../bindings/spi/nvidia,tegra210-quad.yaml    | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> Changes since v2:
> - Fixed version number to match the actual version
> - Added proper changelog section
> - No functional changes from v2
> 
> Changes since v1:
> - Fixed subject prefix to match subsystem (dt-bindings: spi: tegra)
> - Improved commit message formatting to follow Linux coding style
> - Clarified that IOMMU is only required for Tegra234 platform
> - Added explicit disallow for IOMMU on other platforms
> - Removed redundant explanations of what the patch does
> - Fixed commit message to use imperative mood
> 
> Initial Version:
> - Initial implementation of IOMMU property documentation
> - Added iommus property to device tree binding
> - Added support for Tegra234 platform
> - Added explanation of DMA and IOMMU requirements
> 
> diff --git a/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml b/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
> index 48e97e240265..04d3b1a47392 100644
> --- a/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
> +++ b/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
> @@ -10,9 +10,6 @@ maintainers:
>    - Thierry Reding <thierry.reding@...il.com>
>    - Jonathan Hunter <jonathanh@...dia.com>
>  
> -allOf:
> -  - $ref: spi-controller.yaml#
> -
>  properties:
>    compatible:
>      enum:
> @@ -47,6 +44,9 @@ properties:
>        - const: rx
>        - const: tx
>  
> +  iommus:
> +    maxItems: 1
> +
>  patternProperties:
>    "@[0-9a-f]+$":
>      type: object
> @@ -69,6 +69,19 @@ required:
>  
>  unevaluatedProperties: false
>  
> +allOf:
> +  - $ref: spi-controller.yaml#
> +  - if:
> +      properties:
> +        compatible:
> +          const: nvidia,tegra234-qspi

> +    then:
> +      properties:
> +        iommus: true

This is a NOP, no?
Just invert the case above and drop a clause.

> +    else:
> +      properties:
> +        iommus: false
> +
>  examples:
>    - |
>      #include <dt-bindings/clock/tegra210-car.h>
> -- 
> 2.17.1
> 

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