[alsa-devel] ASoC: Hooking a TI CODEC to a i.MX27 MCU

[Stuart Longland]

On Fri, May 28, 2010 at 01:27:12PM +0100, Mark Brown wrote:
> On Fri, May 28, 2010 at 12:06:25PM +1000, Stuart Longland wrote:
> 
> > I have a userspace application that mmaps the registers for SSI2 and
> > AUDMUX, and sets this up, so no big deal ... the clock it receives is
> > about 12.1MHz (12.093MHz according to the frequency counter here).
> 
> In production this should be done in-kernel.

Indeed... I spent some of yesterday afternoon doing exactly this...
which involved some hacking in arch/arm/mach-mx2/clocks_imx27.c... and a
_very_ ugly hack to get at the SSI2 registers in my machine driver.  It
works, but with a few bugs, and will need a big cleanup before I can
even consider putting it in mainline.

> > When I try to play audio; the AUDMUX configuration is as follows:
> 
> > Port:   imx-ssi.0
> > Raw:    cb205000
> > TxFS output from SSI4, TxClk output from SSI4
> > Port is symmetric
> > Data received from SSI4
> 
> > Port:   SSI4
> > Raw:    00001000
> > TxFS input, TxClk input
> > Port is symmetric
> > Data received from imx-ssi.0
> 
> This appears reasonable at first glance.
> 
> > I'll have a look at the Eukrea CPUIMX27 and baseboard SoC support in a
> > moment, since it looks very similar to what we're doing (in that it's a
> > TI I²S CODEC hooked to an i.MX27 on SSI4) ... this might reveal clues
> > as to what I'm doing wrong.
> 
> Have you also checked the pin mux configuration for the i.MX?

I'm not confident on how this is configured; but I have in an array;
tx27_pins[] (defined in arch/arm/mach-mx2/mach-tx27.c):

	/* SSI3 */
	PC28_PF_SSI3_FS,
	PC29_PF_SSI3_RXD,
	PC30_PF_SSI3_TXD,
	PC31_PF_SSI3_CLK,
	/* SSI4 */
	PC16_PF_SSI4_FS,
	PC17_PF_SSI4_RXD,
	PC18_PF_SSI4_TXD,
	PC19_PF_SSI4_CLK,

... which is later set up in tx27_board_init():
	mxc_gpio_setup_multiple_pins(tx27_pins, ARRAY_SIZE(tx27_pins),
			"tx27");

This is what I've seen done on other boards (my mach-tx27.c is based on
mach-mx27ads.c).
Regards,
-- 
Stuart Longland (aka Redhatter, VK4MSL)      .'''.
Gentoo Linux/MIPS Cobalt and Docs Developer  '.'` :
. . . . . . . . . . . . . . . . . . . . . .   .'.'
http://dev.gentoo.org/~redhatter             :.'

I haven't lost my mind...
  ...it's backed up on a tape somewhere.