On Tue, 18 May 2010 21:13:10 +0100 Liam Girdwood lrg@slimlogic.co.uk wrote:
I've also added a patch to remove the mcbsp DMA op mode sysfs set functionality. I think DMA op mode is very specific to the mcbsp client driver _only_ and shouldn't really be changed by userspace. Please let me know if you use this feature and I'll drop this patch.
I've used to say that the DMA op mode is more like use-case not machine specific but I'm not sure is my point valid onemore. I've used to think that low-latency processing would need accurate DMA pointer (op mode == element) while mp3 playback would need low power consumption (op mode == threshold).
Peter: what's the status today how well can we do low-latency processing with threshold mode? IRCC, with your FIFO delay query patches, can we estimate the DMA pointer position with enough accuracy?