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    SubjectRe: [PATCH 6/7] dt-bindings: dmaengine: at_xdmac: add optional microchip,m2m property
    Date
    On 16.10.2020 10:06, Vinod Koul wrote:
    > Hi Eugen,
    >
    > On 16-10-20, 06:45, Eugen.Hristev@microchip.com 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@microchip.com>
    >>>> ---
    >>>> 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
    >

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