[alsa-devel] ALSA SOC Driver (mxs-wm8753)

Mark Brown broonie at kernel.org
Mon Apr 29 22:41:41 CEST 2013

On Mon, Mar 04, 2013 at 06:25:05PM +0000, John Graham wrote:

You should CC maintainers on e-mails, often things just on the list get
lost in the noise.

> The problem now is that the I2S data lines don't look right - the line
> from codec to TX28 looks like a (more-or-less) square wave with the
> same period as the I2S clock, but only going from ~3.1 - ~3.5 V, as
> opposed to the 0 - ~3.3 V I expect. Furthermore, it's a pretty regular
> square wave - it doesn't have all the breaks you see on a working I2S
> data line.

My immediate thought here is that you're probably seeing some sort of
electrical problem if the logic levels aren't being hit - normally this
is because both ends of the link are driving simultaneously.  I'd check
the pin mux settings on the SoC, probably in arch/arm, to make sure that
everything on the SoC is in the correct mode then check that the CPU is
configured as a slave (which sounds like the intended configuration).
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