[alsa-devel] Driver code with mpc5200 pointer problem.

Jaroslav Kysela perex at perex.cz
Mon Apr 27 17:09:27 CEST 2009

On Mon, 27 Apr 2009, Jon Smirl wrote:

> I have fixed all of the other bugs. If I take out the position
> estimation code it fails.
> Jaroslav hasn't commented on this yet....

Appearently, FIFO is too big. I'm working on some changes to take account 
fifo_size to the jiffies based check. Please, set fifo_size correctly in 
your driver. USB drivers with big "URB FIFOs" should be changed as well, 


> On Sun, Apr 26, 2009 at 2:31 PM, Jaroslav Kysela <perex at perex.cz> wrote:
>> On Sun, 26 Apr 2009, Jon Smirl wrote:
>>> If I take this out I get these errors...
>>> ALSA sound/core/pcm_lib.c:264: PCM: hw_ptr skipping! [Q] (pos=11026,
>>> delta=5513, period=5513, jdelta=33/37/0)
>> It means that the period DMA operation is too quick in your case and does
>> not correspond to the timing specified by rate. It might be that the FIFO on
>> path is large or rate set to the codec is not correct. What's HZ value on
>> your system and FIFO size? There is HZ/100 margin in the check now.
> FIFO is 512 bytes, HZ is 300.
> The rate on the codec is correct and the music sounds right.

Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

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