Hi Peter,
Sorry for the late response (and don't hesitate to ping me if I
don't answer, some things get lost in my inbox traffic, sorry).
On Wed, Apr 08, 2009 at 11:18:43AM +0200, Peter Korsgaard wrote:
> >>>>> "Anton" == Anton Vorontsov <avoront...@ru.mvista.com> writes:
>
> Hi,
>
> Anton> The advantages of this:
> Anton> - Don't encourage legacy support;
> Anton> - Less external symbols, less code to compile-in for !MPC832x_RDB
> Anton> platforms.
>
> It's nice with your cleanups, but I wonder how to handle more
> complicated chip select handling than simply toggling a single gpio.
>
> I have a board (or 2 actually, but they are similar in this regard)
> with a mpc8347 using SPI to a number of addon boards. For signal
> integrity reasons the SPI signals are routed to a MUX, so the chip
> select logic has to set the MUX in addition to controlling the CS line
> of the device.
So that's just a bit complicated GPIO controller. I believe you
should describe it in the device tree and use it's muxed lines as
usual GPIOs.
Something ling
muxed_pio: gpio-control...@.. {
#gpio-cells = <2>;
compatible = "..,<board>-muxed-gpios";
reg = <...>;
gpios = <...>; <- specify pure BLK1, BLK2, OPT1, OPT2 GPIOs
gpio-controller;
};
And then,
> I've been using code like this since late 2007, but this patch
> ofcourse breaks it:
>
> static void thinx_spi_activate_cs(u8 cs, u8 polarity)
> {
> static u8 old_cs = 255;
>
> if (cs != old_cs) {
> /* mux setup (cs 2:1)*/
> gpio_set_value(gpio1 + GPIO_SPI_MUX_NOE, 1);
> gpio_set_value(gpio1 + GPIO_SPI_MUX_SEL0, cs&2);
> gpio_set_value(gpio1 + GPIO_SPI_MUX_SEL1, cs&4);
> gpio_set_value(gpio1 + GPIO_SPI_MUX_NOE, 0);
> old_cs = cs;
> }
>
> switch (cs) {
> case 0: gpio_set_value(gpio1 + GPIO_SPI_CS_BKL1, polarity); break;
> case 1: gpio_set_value(gpio1 + GPIO_SPI_CS_BKL2, polarity); break;
> case 2: gpio_set_value(gpio1 + GPIO_SPI_CS_OPT1, polarity); break;
> case 3: gpio_set_value(gpio1 + GPIO_SPI_CS_OPT2, polarity); break;
> }
> }
^^^ Put this logic into the "<board>-muxed-gpios" GPIO controller
driver.
Then spi node would look like this:
spi-control...@.. {
...
gpios = <&muxed_pio cs1 0 /* muxed CS_BLK1 */
&muxed_pio cs2 0 /* muxed CS_BLK2 */
&muxed_pio cs3 0 /* muxed CS_OPT1 */
&muxed_pio cs4 0>; /* muxed CS_OPT2 */
};
Hope this helps,
--
Anton Vorontsov
email: cbouatmai...@gmail.com
irc://irc.freenode.net/bd2
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-dev
