The Tegra210 Quad SPI controller uses internal DMA engines to efficiently
transfer data between system memory and the SPI bus. On Tegra234 platform,
DMA transactions must be properly mapped and protected through IOMMU to
ensure system security and functional correctness. Tegra241 uses external
DMA and doesn't require IOMMU.

Add the iommus property to the device tree binding, making it required
only for Tegra234 platform while explicitly disallowing it for other
platforms including Tegra241.

Signed-off-by: Vishwaroop A <va@nvidia.com>
---
 .../bindings/spi/nvidia,tegra210-quad.yaml    | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml b/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
index 48e97e240265..ac79cb19c81a 100644
--- a/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
+++ b/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
@@ -12,6 +12,25 @@ maintainers:
 
 allOf:
   - $ref: spi-controller.yaml#
+  - if:
+      properties:
+        compatible:
+          enum:
+            - nvidia,tegra234-qspi
+    then:
+      required:
+        - iommus
+  - if:
+      properties:
+        compatible:
+          enum:
+            - nvidia,tegra210-qspi
+            - nvidia,tegra186-qspi
+            - nvidia,tegra194-qspi
+            - nvidia,tegra241-qspi
+    then:
+      properties:
+        iommus: false
 
 properties:
   compatible:
@@ -47,6 +66,9 @@ properties:
       - const: rx
       - const: tx
 
+  iommus:
+    maxItems: 1
+
 patternProperties:
   "@[0-9a-f]+$":
     type: object
-- 
2.17.1

On Tue, May 06, 2025 at 06:08:48PM +0000, Vishwaroop A wrote:
> The Tegra210 Quad SPI controller uses internal DMA engines to efficiently
> transfer data between system memory and the SPI bus. On Tegra234 platform,
> DMA transactions must be properly mapped and protected through IOMMU to
> ensure system security and functional correctness. Tegra241 uses external
> DMA and doesn't require IOMMU.
> 
> Add the iommus property to the device tree binding, making it required
> only for Tegra234 platform while explicitly disallowing it for other
> platforms including Tegra241.
> 
> Signed-off-by: Vishwaroop A <va@nvidia.com>
> ---
>  .../bindings/spi/nvidia,tegra210-quad.yaml    | 22 +++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml b/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
> index 48e97e240265..ac79cb19c81a 100644
> --- a/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
> +++ b/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
> @@ -12,6 +12,25 @@ maintainers:
>  
>  allOf:
>    - $ref: spi-controller.yaml#
> +  - if:
> +      properties:
> +        compatible:

Use 'contains' here so if this is ever a fallback, it works for that 
case.

> +          enum:
> +            - nvidia,tegra234-qspi
> +    then:
> +      required:
> +        - iommus
> +  - if:
> +      properties:
> +        compatible:
> +          enum:
> +            - nvidia,tegra210-qspi
> +            - nvidia,tegra186-qspi
> +            - nvidia,tegra194-qspi
> +            - nvidia,tegra241-qspi

Shouldn't this just be an 'else'? I suppose sometimes an IOMMU might not 
be enabled, but that's policy. Either the h/w has an IOMMU or it 
doesn't.

> +    then:
> +      properties:
> +        iommus: false
>  
>  properties:
>    compatible:
> @@ -47,6 +66,9 @@ properties:
>        - const: rx
>        - const: tx
>  
> +  iommus:
> +    maxItems: 1
> +
>  patternProperties:
>    "@[0-9a-f]+$":
>      type: object
> -- 
> 2.17.1
>

On 06/05/2025 20:08, Vishwaroop A wrote:
> The Tegra210 Quad SPI controller uses internal DMA engines to efficiently
> transfer data between system memory and the SPI bus. On Tegra234 platform,
> DMA transactions must be properly mapped and protected through IOMMU to
> ensure system security and functional correctness. Tegra241 uses external
> DMA and doesn't require IOMMU.
> 
> Add the iommus property to the device tree binding, making it required
> only for Tegra234 platform while explicitly disallowing it for other
> platforms including Tegra241.
> 
> Signed-off-by: Vishwaroop A <va@nvidia.com>
That's another v2? I reviewed one. Some of my comments are still valid.
Can you slow down with new versions and spend some time to read the
feedback you receive?

Best regards,
Krzysztof