Lee Revell wrote: > On Wed, May 28, 2008 at 11:17 AM, Norbert van Bolhuis > <nvbolhuis@xxxxxxxxxxxx> wrote: >> probably this question is asked many times. >> >> Anyway, I hope the experts are willing to help me here. >> I simply don't know how to avoid the DMA overrun that I'm facing >> when playing a tone. > > Not calling snd_pcm_period_elapsed at the right time would cause the > behavior you see. This function wakes up any apps that are waiting > to send data to the sound device. > > Where can I find the source code for your driver? > > Lee > thanks for you answer. I'm a bit reluctant to send the full source code, the driver isn't finished and will go to a customer first. snd_pcm_period_elapsed is called many times and of course on every TX DMA irq, otherwise there wouldn't be calls to snd_pcm_update_hw_ptr_interrupt (see trace). I noticed that I don't suffer from underruns though, only when doing some printk's in the kernel the underruns occur. otherwise everything is fine (DMA keeps running)! The reason I suspected underrun was because whenever my DMA buffer wraps back to the start, the sound stops playing and i hear a lot of noise. When I started to investigate what was going on (with printk's), underruns occured. I still wonder what PCM substream->boundary is, it's defined as "pointer's wrap point". Does this mean it's the same as nr_of_frames_in_DMA_buffer ? -- This message has been scanned for viruses and is believed to be clean _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
