RE: [PATCHv2] wlcore: spi: add wl18xx support

Reizer, Eyal
2016-04-18T05:56:01Z

> >
> > - all wilink family needs special init command for entering wspi mode.
> > extra clock cycles should be sent after the spi init command while the
> > cs pin is high.
> > - switch to controling the cs pin from the spi driver for achieveing the
> > above.
> > - the selected cs gpio is read from the spi device-tree node using the
> > cs-gpios field and setup as a gpio.
> > - See the example below for specifying the cs gpio using the cs-gpios entry
> > &spi0 {
> > ...
> > cs-gpios = <&gpio0 5 0>;
> > ...
> > wlcore: wlcore@0 {
> > compatible = "ti,wl1835";
> > ...
> > ...
> > };
> > };
> >
> > Signed-off-by: Eyal Reizer <eyalr@ti.com>
>
> I don't think this can work in general: not all SPI hosts uses GPIOs for
> controlling CS, so the logic can't work, and it's also a layering violation for the
> driver to look at the parent.
>
> I would suggest fixing this using a new API function from the SPI core, if we
> don't already have a generic way to do it.
>
Originally this is what I have done until I was pointed to the generic cs-gpio mechanism
in the SPI core.
It is a generic mechanism already in the SPI core driver.
See: Documentation/devicetree/bindings/spi/spi-bus.txt

It is also part of the generic spi.h (include/Linux/spi/spi.h), already part of
" struct spi_device" So it seemed redundant adding another mechanism for
implementing the same.
Platform that interact with a wilink need to use it, and platforms that don't
have this capability will probably not interact with a wilink device using SPI.

Best Regards,
Eyal