[PATCH 06/11] dt-bindings: dma: stm32-dma3: introduce st,axi-max-burst-len property

[Amelie Delaunay]

DMA3 maximum burst length (in unit of beat) may be restricted depending
on bus interconnect.

As mentionned in STM32MP2 reference manual [1], "the maximum allowed AXI
burst length is 16. The user must set [S|D]BL_1 lower or equal to 15
if the Source/Destination allocated port is AXI (if [S|D]AP=0)".

Introduce st,axi-max-burst-len. If used, it will clamp the burst length
to that value if AXI port is used, if not, the maximum burst length value
supported by DMA3 is used.

[1] https://www.st.com/resource/en/reference_manual/rm0457-stm32mp2325xx-advanced-armbased-3264bit-mpus-stmicroelectronics.pdf

Signed-off-by: Amelie Delaunay <amelie.delaunay@xxxxxxxxxxx>
---
 .../devicetree/bindings/dma/stm32/st,stm32-dma3.yaml          | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml b/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml
index 38c30271f732e0c8da48199a224a88bb647eeca7..90ad70bb24eb790afe72bf2085478fa4cec60b94 100644
--- a/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml
+++ b/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml
@@ -51,6 +51,16 @@ properties:
   power-domains:
     maxItems: 1
 
+  st,axi-max-burst-len:
+    description: |
+      Restrict AXI burst length in unit of beat by value specified in this property.
+      The value specified in this property is clamped to the maximum burst length supported by DMA3.
+      If this property is missing, the maximum burst length supported by DMA3 is used.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 1
+    maximum: 256
+    default: 64
+
   "#dma-cells":
     const: 3
     description: |
@@ -137,5 +147,6 @@ examples:
                    <GIC_SPI 48 IRQ_TYPE_LEVEL_HIGH>;
       clocks = <&rcc CK_BUS_HPDMA1>;
       #dma-cells = <3>;
+      st,axi-max-burst-len = <16>;
     };
 ...

-- 
2.25.1