On Thu, Oct 29, 2015 at 6:44 AM, Caleb Crome <caleb@xxxxxxxxx> wrote: > On Wed, Oct 28, 2015 at 9:53 PM, Nicolin Chen <nicoleotsuka@xxxxxxxxx> wrote: >> >> I am actually thinking about setting a watermark to a larger number. >> I forgot how the SDMA script handles this number. But if this burst >> size means the overall data count per transaction, it might indicate >> that each FIFO only gets half of the burst size due to dual FIFOs. >> >> Therefore, if setting watermark to 8, each FIFO has 7 (15 - 8) space >> left, the largest safe burst size could be 14 (7 * 2) actually. > > Oh, does this depend on the data size? I'm using 16-bit data, so I > guess the bursts are measured in 2 byte units? Does this mean that > the burst size should be dynamically adjusted depending on word size > (I guess done in hw_params)? > >> Nicolin Okay, so wm=8 and maxburst=14 definitely does not work at all,. wm=8, maxburst=8 works okay, but still not perfect. I just discovered some new information: With wm=8 and maxburst=8 (which is my best setting so far), I just captured a problem at the very start of playing a file, and restarted enough times to capture it starting wrong: Instead of the playback starting with (hex numbers: my ramp file has first nibble as channel, second nibble as frame) frame 0: 00, 10, 20, 30, 40, 50, 60, 70, 80, 90, a0, b0, c0, d0, e0, f0 frame 1: 01, 11, 21, 31, 41, 51, 61, 71, 81, 91, a1, b1, c1, d1, e1, f1 It started with: frame 0: 00, 00, 10, 20, 30, 40, 50, 60, 70, 80, 90, a0, b0, c0, d0, e0 frame 1: f0, 01, 11, 21, 31, 41, 51, 61, 71, 81, 91, a1, b1, c1, d1, e1 So, the transfer started wrong right out of the gate -- with an extra sample inserted at the beginning. Again, my setup is: 1) use scope to capture the TDM bus. Trigger on first data change 2) aplay myramp.wav 3) If okay, ctrl-c and goto 2. 4) The capture below shows everything off by 1 sample. The capture is here: https://drive.google.com/open?id=0B-KUa9Yf1o7iOXFtWXk2ZXdoUXc This test definitely reveals that there is a startup issue. Now for the $64,000 question: what to do with this knowledge? I'm quite unfamiliar with how the DMA works at all. I'll start poking around the DMA I guess. Thanks, -Caleb _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
