>-----Original Message----- >From: Jaroslav Kysela [mailto:perex@xxxxxxxx] >Sent: Thursday, July 02, 2009 1:39 PM >To: Harsha, Priya >Cc: alsa-devel@xxxxxxxxxxxxxxxx; tiwai@xxxxxxx >Subject: Re: Help required with debugging > >On Thu, 2 Jul 2009, Harsha, Priya wrote: > >> Why is runtime->hw_ptr_jiffies updated in hw_ptr()? This should be only >> updated in the interrupt context right? > >The idea of hw_ptr_jiffies is to have a check if real-time clock in sync >with the DMA buffer position. If your hardware does block transfers and is >not able to return fine position in period set SNDRV_PCM_INFO_BATCH flag. Thanks a lot. Setting the runtime->hw.info = SNDRV_PCM_INFO_BATCH in the ops->prepare(), helps getting past the issue. Its true that the hardware is doing a batch transfer of period_size into the dma_buffer of ALSA. >But it's rather a workaround than a proper fix, because timestamps are >updated but the ring buffer position is not moved (which brokes the idea >to have a relation between the ring buffer position and the real-time >clock). Actually the firmware does not update the timestamp till the period size is reached, i.e., the firmware increments the timestamp with period_size and transfers the same to the dma_buffer. > >I think that this sort of drivers might require to implement the >SNDRV_PCM_POS_KEEP return value in case when position does not change from >last read to notify midlevel PCM code that they're not able to handle fine >pointer resolution. I don't find this return value in the ALSA code, can you help me with more details of what needs to be returned and where. > >Also, hardware with large FIFOs should update properly runtime->delay >value now. I am not finding a field called delay in runtime structure. Where can I find it...and is there a documentation/comment on what this value needs to hold? > > Jaroslav > >----- >Jaroslav Kysela <perex@xxxxxxxx> >Linux Kernel Sound Maintainer >ALSA Project, Red Hat, Inc. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
