[RFC/DRAFT] SPI OF bindings, MMC-over-SPI, chip-selects and so on

Grant Likely grant.likely at secretlab.ca
Thu May 22 02:51:37 EST 2008

On Wed, May 21, 2008 at 9:41 AM, Anton Vorontsov
<avorontsov at ru.mvista.com> wrote:
> Hi all,
> This is just a bait for further discussion of OF/SPI, chip-selects,
> e.t.c.
> I've converted the spi_mpc83xx to the OF driver (using Grant's
> SPI_MASTER_OF work + some additions), and implemented MMC-over-SPI
> bindings. This stuff extensively using GPIOs, and I think this will
> work for the "bridged SPI" too, since the SPI bridge could be
> represented as GPIO controller (inside the SPI controller node).

The GPIOs case doesn't bother me too much.  If the controller supports
GPIO chip selects (and pretty much all of them could I think) then the
SPI master driver just needs to specify that it supports N chip
selects and have a gpios property that lists all the relevant GPIOs
(just like you've done).  So I think this bit is looking good.

More complex cases would still probably need some form of spi-bridge
node (and most likely requiring changes to the SPI infrastructure to
make bridging easy; but that is just driver details).

The board info handling I think requires more thought... (details in
another email)


Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.

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