[alsa-devel] Please help in adding ams-delta support to ASoC

Peter Ujfalusi peter.ujfalusi at nokia.com
Wed May 27 07:57:27 CEST 2009

On Tuesday 26 May 2009 16:17:23 ext Janusz Krzysztofik wrote:
> Hi,
> I am trying to add sound support for ams-delta omap machine, yet without
> much success.
> Three years ago, Mark Underwood created an omap-alsa compatible driver
> that basically worked[1]. It was derieved from similiar driver for aic23
> codec found on omap osk machine. It looks like Mark has never managed to
> finish his work. It's not clear for me if he has found that getting a
> working fullduplex sound is technically impossible on a voice modem
> codec, shared among modem and cpu, controlable only from modem side
> afaik, but I have decided to give it a try.
> Since Mark's initial work, omap-alsa framework has been depreciated in
> favour of soc-omap. API changes are so significant that Mark's code is
> rather not useable directly any more. However, I am trying to use it as
> a starting point, by comparing it against it's prototype osk/aic23 code.
> Following Mark, I am trying to derieve the new ams-delta sound driver
> from current asoc driver for omap osk9512. For codec part, I decided to
> base my work on much more simple ad73311 rather that tlv320aic23.
> Comparing Mark's code agaist it's osk/aic23 prototype, I can see the
> folowing significant changes:
> 1. rate tables/bitmaps found in hw_constraint_rates,
> snd_omap_alsa_playback and snd_omap_alsa_capture structures limited to
> 8kHz, 2. hardware related code found in codec_configure_dev(),
> codec_clock_on() and codec_clock_off() callback functions replaced with
> ams-delta hardware specific code that switches the codec DAI pins from
> modem chip to mcbsp cpu interface and back,
> 3. codec_set_samplerate() and all mixer related functions replaced with
> stubs.
> 4. the following McBSP register settings changes:
> +	.xcr2 = XPHASE | XWDLEN2(OMAP_MCBSP_WORD_16) | XFRLEN2(0),
> +	.srgr1 = CLKGDV(0),
> +       .srgr2 = GSYNC,
> -	.pcr0 = CLKXP | CLKRP,  /* mcbsp: slave */

Since I don't have the original osk/aic23 thing, this does not mean to much...
Just a bit confusing. The configuration suggest slave McBSP with NB_IF 
polarity, dual phase format, 16 bit words, 16*2 long frames, the FS pulse is 
probably a pulse... Suggesting kind of DSP mode, but with not so correct 
configuration, which happens to be working.

> I have found points 1. to 3. rather trivial to implement in new
> framework. Regarding point 4., it looks like detailed register settings
> are now done inside omap-mcbsp.c, based on machine specified format, so
> I have to find out what format should be specified for ams-delta. Please
> correct me if I am missing something.

Yes, that is correct. What you need for the point 4:
Interface format of the cx20442 codec (I2S, DSP_A, DSP_B, etc)
Clock polarities.
Does the codec provides the clocks (bit, frame sync) - codec master or slave

When you know these the soc/omap/arms-delta.c can configure the CPU dai with:
snd_soc_dai_set_fmt(cpu_dai, ...

> There was one more modification in Mark's code, addressing dma chaining
> problem on omap15xx hardware, but as far as I could see, the problem was
> already solved in the asoc omap framework.
> Initially, I based my work on ompenembedded provided linux-omap.git
> revision 90e758af52ba803cba233fabee81176d99589f09. The results were
> rather poor - total system hangup after first device access, with no
> single message. So I have switched to linux-2.6.30-rc5 and now I can
> safely access the device, however it does not work as expected. aplay
> and arecord wait forever, cat to/from /dev/dsp breaks with hardware
> error messgae.
> DMA interrput counters stay at 0.

This means that the McBSP module is not transmitting/receiving any data.
Which suggests that the clocking is not working in your setup. Check the slave 
master mode for the codec.
Also worth checking the PIN configuration for the McBSP1 module, just in case 
it is correct.

> However, codec
> switching that I do from machine->ops->startup/shutdown seems working,
> as modem stops producing any sounds while the alsa device is in use and
> gets back thereafter.
> First of all, I'd like to make sure if my problem is related to my code
> only. As I am new in these areas, I would like to ask you if the omap
> asoc framework is stable enough to relay on.

I believe that it is stable enough.

> If yes, could you please
> look at my dirty code (attached) an give me some hints? I can provide
> you with more information if necessary.

Given that it is still early morning, I could not find anything that would 
prevent it to be somehow working...

> Regards,
> Janusz


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