I am trying to write a driver for the Blackfin BF537 processor on a custom board that has two CS42448 CODECs connected to SPORT0. I am using TDM and there are 8 channels per frame on each data line (primary and secondary). My DMA buffer must interleave the data for the two data lines (for a total of 16 channels of data per frame). I have completed all of this and the driver will sometimes work properly but I am having underrun problems. I would like to use snd_async_add_pcm_handler as it is used in the /test/pcm.c example but it seems as though an underrun occurs at regular intervals causing the PCM prepare function to be called again (this results in a tone that sounds good but only for a short time before it stops and then starts again). There is plenty of time for the data to be transferred. I feel as though the driver is not calling snd_pcm_period_elapsed fast enough. At the moment, I call snd_pcm_period_elapsed from within a callback function that occurs every time a DMA period elapse occurs. I have been working on this for quite a while now. Is there someone who can look at the driver code for me or provide detailed information on when ALSA expects to have snd_pcm_period_elapsed get called to avoid an underrun? The other thing that is strange is that I have to explicitly set the period size for aplay to work. For example: aplay --period-size=1024 test.wav which gives me a period time of 21333 but when I use this period time with the /test/pcm.c sample that is provided the tone still does not sound right (although it does seem to improve) I am about ready to bypass ALSA entirely but I hate the idea of breaking from standards (not to mention having to rewrite an entire audio interface). Any help would be greatly appreciated! You can check out the driver here: http://www.alcorn.com/ftp/swap/ami_cs42448.zip Thank you, Adam Adam Rosenberg Software Engineer Alcorn McBride Inc. 3300 South Hiawassee Building 105 Orlando, FL 32835 (407) 296 - 5800 ext. 5490 _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
