[alsa-devel] Please help in adding ams-delta support to ASoC
peter.ujfalusi at nokia.com
Tue Jun 9 09:12:41 CEST 2009
On Saturday 06 June 2009 20:42:12 ext Janusz Krzysztofik wrote:
> I'm not sure how that could happen, but I was wrong with some of those
> figures. After looking at the scope several more times I can only confirm
> that master clock really runs at 2MHz (0,5µs period). Frame sync is rather
> closer to 8kHz (~125µs period) than previously estimated 10kHz, with the
> same symmetric (50% fill) shape as before. But bit clock is very different
> from what I have seen before. It runs at 2MHz in 9µs long packets (18
> periods), those are repeated every half period of frame sync (~62µs /
> 16kHz), ie every frame sync edge, both rising and falling. There is also a
> signal present on codec data output: 4µs long packets (8 bits each?) every
> ~62µs (16 kHz).
I'm kind of bad at visualizing things, is it possible to put somewhere the
screenshoot of the scope showing at least one sample?
> Is it possible that the codec speeks I2S, with 8-bit word, 1 word per
> frame, 2 channels at 8kHz each? Or 1 channel at 16 kHz? From what I can
> read in modem documentation, this should rather be one 8-bit channel at
> 8kHz. Anyway, can the transmission format I have seen ont the oscilloscope
> be matched against any format that mcbsp can be set with current code?
I have been looking for clues around the net, and it seams that the codec in
question has stereo 16 bit format.
> I'm still far from understanding mcbsp, but I wonder what happens if the
> bit clock stops ater 18th bit while maybe mcbsp expects more. Perhaps this
> is the cause of dma interrupts not being generated?
Without actual OMAP1510 HW it is really hard to tell what can be the problem.
What I would do, if I had a HW:
1) See if the DMA actually was running and it is 'just' about the missing
@@ -193,11 +193,15 @@ static int omap_pcm_trigger(struct snd_pcm_substream
*substream, int cmd)
prtd->period_index = 0;
+ printk("omap_pcm_trigger START: DMA pointer at 0x%08x\n",
+ printk("omap_pcm_trigger STOP: DMA pointer at 0x%08x\n",
prtd->period_index = -1;
Than start a playback, and stop it with CTRL+C, see if the two pointers are
2) I would I think try to port the 2.6.28 pure ALSA version to the head of l-
o, with minimal (only the needed) changes and see if it is still working.
I know, this is a long shot, but at least we can be sure, that the problem is
in the ASoC McBSP/DMA integration or it is something else.
Meanwhile I'll try to locate one OMAP1510 based board to try to help with this
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