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    SubjectRe: [PATCH v3 03/22] dt-bindings: arm: scmi: add ARM MHU specific mailbox client bindings
    On Mon, Oct 9, 2017 at 7:22 PM, Rob Herring <robh@kernel.org> wrote:
    > On Fri, Oct 6, 2017 at 9:26 PM, Jassi Brar <jassisinghbrar@gmail.com> wrote:
    >> On Fri, Oct 6, 2017 at 9:24 PM, Rob Herring <robh@kernel.org> wrote:
    >>> On Fri, Oct 6, 2017 at 6:01 AM, Jassi Brar <jassisinghbrar@gmail.com> wrote:
    >>>> On Fri, Oct 6, 2017 at 4:50 AM, Rob Herring <robh@kernel.org> wrote:
    >>>>> On Thu, Sep 28, 2017 at 02:11:27PM +0100, Sudeep Holla wrote:
    >>
    >>>>>
    >>>>>> +- mbox-data : For each phandle listed in mboxes property, an unsigned 32-bit
    >>>>>> + data as expected by the mailbox controller
    >>>>>
    >>>>> Shouldn't that be cells as part of mboxes property?
    >>>>>
    >>>> A MHU client can send any number of commands (such u32 values) over a channel.
    >>>> This client (SCMI) sends just one command over a channel, but other
    >>>> clients may/do send two or more.
    >
    > The above definition doesn't support 2 or more as it is 1-1 with channels.
    >
    I thought you suggested to make controller driver accept the command
    as another cell in client's mboxes property.
    Which we can't do.

    >>> Okay, then I guess I don't understand why this is in DT.
    >>>
    >> Yeah the client has to provide code (u32 value) for the commands it
    >> sends, and that value is going to be platform specific. For example,
    >> on Juno the ITS_AN_SCMI_COMMAND may be defined as BIT(7) while on my
    >> platform it may be 0x4567
    >>
    >> For MHU based platforms, it becomes easy if the u32 is passed from DT.
    >> And that should be ok since that is like a h/w parameter - a value
    >> chosen/expected by the remote firmware.
    >
    > Could it ever be more than 1 cell?
    >
    SCMI sends sub-commands via SHMEM, so it is always going to be 1cell for _scmi_.
    However many firmwares are unlikely to use just one command over a
    channel - say, the protocol is trivial or the linux and remote have no
    SHMEM.

    > I guess being in DT is fine, but I'm still not sure about the naming.
    > The current name suggests it is part of the mbox binding. Do we want
    > that or should it be SCMI specific? Then "data" is vague. Perhaps
    > "scmi-commands"?
    >
    Sure. I have no problem with whatever we wanna call it.

    thnx

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