On 16.10.2020 10:06, Vinod Koul wrote: > 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 for explaining, I will change accordingly then. Eugen > > Thanks > -- > ~Vinod >
