[alsa-devel] trouble with alsa, wolfson, and TI OMAP35xx McBSP

Mark Brown broonie at opensource.wolfsonmicro.com
Thu Apr 23 14:05:52 CEST 2009

On Thu, Apr 23, 2009 at 02:52:24PM +0300, Peter Ujfalusi wrote:

> I have a theory, which needs to be checked for the startup switch in OMAP:
> I think what is happening, that the McBSP module got enabled earlier then the 
> DMA is started. This leads to and underrun situation in McBSP (no data in the 
> buffer), so McBSP will transmit _something_ when the start condition for the 
> I2S is met. When the DMA starting to push data to McBSP, than valid data will 
> be shifted out.
> McBSP is shifting word by word manner. So if the first word transmit need to 
> be done, when the buffer is empty, it starts to shift the word, than the data 
> arrives from the DMA,  the next word will be valid data -> you will have a 
> nice channel switch.

> Is this makes sense?

Sounds entirely plausible to me.

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