On 23.09.2020 02:33, Rob Herring wrote:

On Mon, Sep 14, 2020 at 05:09:55PM +0300, Eugen Hristev wrote:

quoted

Add optional microchip,m2m property that specifies if a controller is
dedicated to memory to memory operations only.

Signed-off-by: Eugen Hristev <redacted>
---
  Documentation/devicetree/bindings/dma/atmel-xdma.txt | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/dma/atmel-xdma.txt b/Documentation/devicetree/bindings/dma/atmel-xdma.txt
index 510b7f25ba24..642da6b95a29 100644
--- a/Documentation/devicetree/bindings/dma/atmel-xdma.txt
+++ b/Documentation/devicetree/bindings/dma/atmel-xdma.txt

@@ -15,6 +15,12 @@ the dmas property of client devices.
      interface identifier,
      - bit 30-24: PERID, peripheral identifier.

+Optional properties:
+- microchip,m2m: this controller is connected on AXI only to memory and it's
+     dedicated to memory to memory DMA operations. If this option is
+     missing, it's assumed that the DMA controller is connected to
+     peripherals, thus it's a per2mem and mem2per.

Wouldn't 'dma-requests = <0>' cover this case?

Rob

Hi Rob,

I do not think so. With requests = 0, it means that actually the DMA 
controller is unusable ?
Since you suggest requests = 0, it means that it cannot take requests at 
all ?
I do not find another example in current DT with this property set to zero.

Eugen