[alsa-devel] [PATCH 1/4] ASoC: Use network mode with 2 slots for 16-bit stereo in pxa-ssp/Zylonite

[pHilipp Zabel]

On Wed, Mar 4, 2009 at 9:45 PM, pHilipp Zabel <philipp.zabel at gmail.com> wrote:
> On Wed, Mar 4, 2009 at 2:34 AM, Daniel Mack <daniel at caiaq.de> wrote:
>> Hi Phillip,
>>
>> glad to see someone is wasting time with that issue, too :)
>>
>> On Tue, Mar 03, 2009 at 04:10:51PM +0100, Philipp Zabel wrote:
>>> For consistency with 24-bit and 32-bit modes, don't send 16-bit stereo
>>> in one 32-bit transfer. Use 2 slots instead on Zylonite. It should result
>>> in exactly the same behaviour.
>>> Now it is possible to use 16-bit single slot transfers in pxa-ssp, which
>>> are needed for Magician to get two frame clock pulses per sample
>>> (one for each channel).
>>
>> We've been fiddling around with these modes and registers for
>> another two days in a row now and figured out that literally all the
>> documentation about these registers is entirly bogus. In particular,
>> the network mode with the associated timeslots simply does not work at
>> all, according to our measurements.
>>
>> Hence the question: how does your I2S signal look like at the moment?
>> How many clocks do you measure in one frame cylce, how many of them are
>> actually filled with data? And which format does the userspace use to
>> send samples in?
>
> Unfortunately, I can't measure anything. I don't own an oscilloscope
> and I don't even know if there are useful test points on the phone's
> mainboard.
> Also, I've come to the conclusion that on Magician there has to be
> some kind of flip-flop between the PXA272's SSPFRMCLK and the codec's
> LRCLK input.
[...]

Unfortunately, this means that if I play sound for an odd number of
frame clocks, the next playback will have left and right channels
switched.
I checked this by measuring the number of frames sent with OSCR8.
Is there a way to force pxa-ssp to only ever stop playback after an
even number of frames?

regards
Philipp