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    SubjectRe: [PATCH v3 07/14] dt-bindings: dma: ti: Add document for K3 UDMA
    On Tue, Oct 15, 2019 at 12:29 PM Peter Ujfalusi <peter.ujfalusi@ti.com> wrote:
    >
    > Rob,
    >
    > On 10/11/19 10:30 AM, Peter Ujfalusi wrote:
    > >
    > > I have already moved the TR vs Packet mode channel selection, which does
    > > make sense as it was Linux's choice to use TR for certain cases.
    > >
    > > If I move these to code then we need to have big tables
    > > struct psil_config am654_psil[32767] = {};
    > > struct psil_config j721e_psil[32767] = {};
    >
    > After thinking about this a bit more, I think we can move all the PSI-L
    > endpoint configuration to the kernel as not all the 32767 threads are
    > actually in use. Sure it is going to be some amount of static data in
    > the kernel, but it is an acceptable compromise.
    >
    > The DMA binding can look like this:
    >
    > dmas = <&main_udmap 0xc400>,
    > <&main_udmap 0x4400>;
    > dma-names = "tx", "rx";
    >
    > or
    > dmas = <&main_udmap 0x4400 UDMA_DIR_TX>,
    > <&main_udmap 0x4400 UDMA_DIR_RX>;
    > dma-names = "tx", "rx";
    >
    > If I keep the direction.
    > 0xc400 is destination ID, which is 0x4400 | 0x8000 as per PSI-L
    > specification.
    > In the TRM only the source threads can be found as a map (thread IDs <
    > 0x7fff), but the binding document can cover this.
    >
    > This way we don't need another dtsi file and I can create the map in the
    > kernel.
    >
    > This will hide some details of the HW from DT, but since the PSI-L
    > thread configuration is static in hardware I believe it is acceptable.
    >
    > However we still have uncovered features in the binding or in code, like
    > a case when the RX does not have access to the DMA channel, only flows.
    > Not sure if I should reserve the direction parameter as an indication to
    > this or find other way.
    > Basically we communicate on the given PSI-L thread without having a DMA
    > channel as other core is owning the channel.
    >
    > What do you think?

    Seems like a reasonable solution though I don't really follow the last issue.

    Rob

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