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    SubjectRe: [PATCH RFC 0/5] *** SPI Slave mode support ***
    Hi Jiada,

    On Fri, Apr 14, 2017 at 7:39 AM, Jiada Wang <jiada_wang@mentor.com> wrote:
    > On 04/13/2017 12:47 PM, Geert Uytterhoeven wrote:
    >> On Thu, Apr 13, 2017 at 2:59 PM, Mark Brown<broonie@kernel.org> wrote:
    >>> On Thu, Apr 13, 2017 at 05:13:59AM -0700, jiada_wang@mentor.com wrote:
    >>>> From: Jiada Wang<jiada_wang@mentor.com>
    >>>>
    >>>> v1:
    >>>> add Slave mode support in SPI core
    >>>> spidev create slave device when SPI controller work in slave mode
    >>>> spi-imx support to work in slave mode
    >>>
    >>> Adding Geert who also had a series doing this in progress that was
    >>> getting very near to being merged.
    >>
    >> Thank you!
    >>
    >> Actually my plan is to fix the last remaining issues and resubmit for
    >> v4.13.
    >
    > I noticed your patch set for SPI slave support,
    > (I am sure you can find out some of the change
    > in this patch set is based on your work).
    > we have similar requirement to add slave mode support to ecspi IP on imx6
    > Soc.
    >
    > Our use case is to use spidev as an interface to communicate with external
    > SPI master devices.
    > meanwhile the SPI bus controller can also act as master device to send data
    > to other
    > SPI slave devices on the board.

    That sounds a bit hackish to me. SPI was never meant to be a multi-master bus.
    While it can be done, you will need external synchronization (signals) to
    avoid conflicts between the SPI masters.

    > I found in your implementation, SPI bus controller is limited to either work
    > in master mode or
    > slave mode, is there any reasoning to not configure SPI mode based on SPI
    > devices use case?

    If you really need both master and slave support, you can use 2 subnodes
    in DT, the first representing the master, the second the slave.

    Mark, what's your opinion about this?

    Thanks!

    Gr{oetje,eeting}s,

    Geert

    --
    Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

    In personal conversations with technical people, I call myself a hacker. But
    when I'm talking to journalists I just say "programmer" or something like that.
    -- Linus Torvalds

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