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 06/05/2025 19:58, 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.


Please wrap commit message according to Linux coding style / submission
process (neither too early nor over the limit):
https://elixir.bootlin.com/linux/v6.4-rc1/source/Documentation/process/submitting-patches.rst#L597

I don't think you read the review, just skimmed. I explained there how
to construct subject prefix and gave a link explaining it better.

Can you reach to your colleagues to help in upstreaming process to avoid
easy mistakes? Many companies have internal checklists or internal
guides helping in that...

> 
> 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.

Why requiring it for Tegra234? Do not explain what you did - we see it
easily. Explain what we do not see, so why you are breaking ABI.


Best regards,
Krzysztof