From: Conor Dooley <conor@kernel.org>
Sent: Thursday, January 29, 2026 7:45 PM

On Wed, Jan 28, 2026 at 11:51:30PM +0200, Cosmin Tanislav wrote:

quoted

All supported SoCs have multiple DMA controllers that can be used with
the RSPI peripheral. The current bindings only allow a single pair of RX
and TX DMAs.

The DMA core allows specifying multiple DMAs with the same name, and it
will pick the first available one.

There is an exception in the base dt-schema rules specifically for
allowing this behavior (dtschema/schemas/dma/dma.yaml).

dma-names:
  anyOf:
    - uniqueItems: true
    - items:
        # Hack around Renesas bindings which repeat entries to support
        # multiple possible DMA providers
        enum: [rx, tx]

Allow multiple DMAs to have the same name and only restrict the possible
names of the DMA channels, not their count.

For RZ/T2H and RZ/N2H SoCs, limit the number of DMA channels to 6, as
they have 3 DMA controllers.

What's the rationale behind not setting minItems to 6 here

quoted

For RZ/V2H and RZ/V2N SoCs, limit the number of DMA channels to 10, as
they have 5 DMA controllers.

and to 10 here? Do any of the spi controllers on these SoCs not have the
ability to use all of the available dma controllers?

I left minItems to 2 in case it is necessary to wire up SPI to only a
subset of the DMA controllers, maybe for performance reasons in a
board-specific dts?

I know that dts is only supposed to describe the hardware itself, but for
now this would be the only way to pre-select which DMA controller is used
for a specific IP.

Let me know your thoughts.

quoted

Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
---

V3:
 * impose proper maxItems for each device
 * impose maxItems for dmas property

V2:
 * new patch

 .../bindings/spi/renesas,rzv2h-rspi.yaml         | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml

b/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml

quoted

index a588b112e11e..cf8b733b766d 100644

--- a/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml
+++ b/Documentation/devicetree/bindings/spi/renesas,rzv2h-rspi.yaml

@@ -58,12 +58,16 @@ properties:
       - const: tresetn

   dmas:
-    maxItems: 2
+    minItems: 2
+    maxItems: 10

   dma-names:
+    minItems: 2
+    maxItems: 10
     items:
-      - const: rx
-      - const: tx
+      enum:
+        - rx
+        - tx

   power-domains:
     maxItems: 1

@@ -121,6 +125,12 @@ allOf:
         resets: false
         reset-names: false

+        dmas:
+          maxItems: 6
+
+        dma-names:
+          maxItems: 6
+
 unevaluatedProperties: false

 examples:
--

2.52.0