Hi Eugen, On 16-10-20, 06:45, Eugen.Hristev@xxxxxxxxxxxxx wrote: > On 23.09.2020 02:33, Rob Herring wrote: > > > On Mon, Sep 14, 2020 at 05:09:55PM +0300, Eugen Hristev wrote: > >> Add optional microchip,m2m property that specifies if a controller is > >> dedicated to memory to memory operations only. > >> > >> Signed-off-by: Eugen Hristev <eugen.hristev@xxxxxxxxxxxxx> > >> --- > >> 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. Not really, dma-requests implies "request signals supported" which are used for peripheral cases. m2m does not need request signals, so it is very reasonable to conclude that dma-requests = <0> would imply no peripheral support and only m2m support. Thanks -- ~Vinod
