Messages in this thread | | | Date | Fri, 17 Apr 2009 16:23:59 +0400 | From | Anton Vorontsov <> | Subject | Re: [PATCH 6/6] powerpc/fsl_soc: Isolate legacy fsl_spi support to mpc832x_rdb boards |
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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 <avorontsov@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-controller@.. { #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-controller@.. { ... 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: cbouatmailru@gmail.com irc://irc.freenode.net/bd2
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