Re: i.MX: GPIO based SPI chip selects question

[Baruch Siach <baruch-NswTu9S1W3P6gbPvEgmw2w@public.gmane.org>]

Hi Wayne,

On Fri, Oct 28, 2011 at 02:06:16PM +0100, Wayne Tams wrote:
> Can I use GPIO pins on my i.mx53 for SPI chip select, I have found little
> on the web that can help me, I am hoping that it is straight-forward enough
> for me to implement it? Perhaps there is a macro that I can use in the
> spi_board_info structure that will let me declare the GPIO?

If you are using the mainline kernel then the SPI driver 
(drivers/spi/spi-imx.c) supports the use of GPIO lines for chip-select 
exclusively. You can find an i.MX53 specific example in 
arch/arm/mach-mx5/board-mx53_evk.c (look for the mx53_evk_spi_data struct).  
This example demonstrate the use of two GPIOs for chip-select, but the list of 
chip-selects can be longer.

Since you appear to be using the Freescale supplied kernel (as I infer from 
your previous question on this list), you are probably using different driver.  
This driver (likely 
http://opensource.freescale.com/git?p=imx/linux-2.6-imx.git;a=blob;f=drivers/spi/mxc_spi.c;h=8c722686a0e1a419b417c0e2f98a4d6f028cf02e;hb=a1cd8a787a18da69ac4e48cfc876623bd7323799) 
does not support GPIOs for chip-select.

Freescale seem to have abandoned their in-house non mainlined SPI driver in a 
later version of their kernel (rel_imx_2.6.38_11.09.01 tag in 
http://opensource.freescale.com/git) so you may want to update your kernel.

baruch

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