On Mon, May 19, 2008 at 07:09:00PM +0200, Gary Jennejohn wrote: > On Mon, 19 May 2008 09:57:21 -0600 > "Grant Likely" <[EMAIL PROTECTED]> wrote: > > > On Mon, May 19, 2008 at 7:17 AM, Guennadi Liakhovetski > > <[EMAIL PROTECTED]> wrote: > > > On Fri, 16 May 2008, Grant Likely wrote: > > > > > >> + However, the binding does not attempt to define the specific method > > >> for > > >> + assigning chip select numbers. Since SPI chip select configuration > > >> is > > >> + flexible and non-standardized, it is left out of this binding with > > >> the > > >> + assumption that board specific platform code will be used to manage > > >> + chip selects. Individual drivers can define additional properties > > >> to > > >> + support describing the chip select layout. > > > > > > Yes, this looks like a problem to me. This means, SPI devices will need > > > two bindings - OF and platform?... Maybe define an spi_chipselect > > > OF-binding? > > > > Actually, spi devices have *neither*. :-) They bind to the SPI bus. > > Not the platform bus or of_platform bus. But that is Linux internal > > details; this discussion is about device tree bindings. > > > > Note that I did say that drivers can define additional properties for > > supporting chip select changes as needed. I'm just not attempting to > > encode them into the formal binding. There is simply just too many > > different ways to manipulate chip select signals and so I don't feel > > confident trying to define a *common* binding at this moment in time. > > At some point in the future when we have a number of examples to > > choose from then we can extend this binding with chip select related > > properties. > > > > As for the Linux internals, the 5200 SPI bus driver that I posted > > exports a function that allows another driver to call in and > > manipulated the CS lines before the transfer. It isn't the prettiest > > solution, but I'm not locked into the approach and that gives some > > time to consider cleaner interfaces. > > > > I sort of hesitate to hijack this thread, but since we're discussing SPI > and chip selects... > > I have a driver for the SPI controller in the 440EPx. This controller > is very simple and does not have any internal support for a chip select. > The controller seems to also be in the 440GR and 440EP, and may be in > other AMCC CPUs too. > > All chip selects must be done using GPIO. In fact, the board for which > I developed this driver, a modified sequoia, actually uses 2 chip selects. > > My problem was, and is, that there's no generic GPIO support for powerpc. > At least, not that I'm aware of. Please tell me if I'm wrong.
Documentation/powerpc/booting-without-of.txt VIII - Specifying GPIO information for devices. And include/linux/of_gpio.h + drivers/of/gpio.c. Soon I'll post some patches for mpc83xx_spi showing how to use GPIOs for the SPI chip selects. -- Anton Vorontsov email: [EMAIL PROTECTED] irc://irc.freenode.net/bd2 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
