On Mon, Apr 19, 2010 at 12:04:30PM -0500, H Hartley Sweeten wrote:
> On Friday, April 16, 2010 9:59 PM, Mika Westerberg wrote:
...
> > when it wants to assert/deassert the chip select. I don't see how this is
> > limited to built-in GPIOs only (maybe I'm missing something). Now it is in
> > responsibility of platform board files to allocate necessary chipselect
> > lines,
> > and translate 'spi->chip_select' and 'value' to something meaningful.
>
> The way you are currently handling the chip select limits you to the built-in
> GPIO's because the 'gpio_request' happens early in the platform init before
> any
> external gpio expanders might be available.
>
> The best example is if your first SPI device is actually a GPIO expander that
> is chip selected by a built-in GPIO. This GPIO expander is then used to
> provide
> the chip selects for additional SPI devices on the bus.
Ok.. got it. I didn't consider that one.
> >> Ryan and I worked out a runtime setup/cleanup for the spi device chip
> >> selects
> >> in the spi driver I have in my tree. I will take a look at it and see how
> >> much trouble it will be to implement in your driver.
> >
> > Ok.
>
> I have a patch almost working.
>
> Have you had time to implement any of the changes that Grant Likely proposed?
Mostly yes. I'm still considering whether I should drop the polling mode.
> One of them dealt with the ep93xx_spi_{de}select_device functions. Before I
> post my proposed changes I would like to make sure it is based on your most
> current code.
I changed chipselect functions to be something like (espi->cs_control is copied
from info structure):
if (espi->cs_control)
espi->cs_control(spi->chip_select, !!(spi->mode & SPI_CS_HIGH),
espi->cs_data);
I'm not exactly sure whether this is what Grant meant, however.
> BTW, my patch will also handle Martin Guy's issue with using a null chip
> select.
Yeah. I also have that fixed.
Do you want me to send next revision so that you can base your proposed changes
on top of that or how to proceed?
> Actually, the chip-select isn't really null since the SFRMOUT line is still
> asserted (active-low) during any SPI transfer but the effect is still the
> same.
Too bad that SFRMOUT cannot be used as GPIO, we could then use it as proper
software controlled chipselect ;)
Thanks,
MW
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