Hi Sakamoto-san > > Power Down Release Command (PMVR, PMDAC, RSTN, PMDA1-PMDA6) > > which are located on PW_MGMT1 / PW_MGMT3 register must be > > write again after at least 5 LRCK cycle or later on each command. > > Otherwise, Playback volume will be 0dB. > > Basically, it should be > > > > 1. PowerDownRelease by Power Management1 <= call 1.x after 5LRCK > > 1.x Dummy write to Power Management1 > > 2. PowerDownRelease by Power Management3 <= call 2.x after 5LRCK > > 2.x Dummy write to Power Management3 > > > > To avoid too many dummy write, this patch is merging these. > > > > 1. PowerDownRelease by Power Management1 > > 2. PowerDownRelease by Power Management3 <= call after 5LRCK > > 2.x Dummy write to Power Management1/3 <= merge dummy write > > > > This patch adds dummy write when Playback Start timing. > > > > Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx> > > --- (snip) > Please add enough descriptions that kernel's timer functionality > cannot guarantee accuracy of expiration of timer for 5 phases of word > select clock on usual serial sound interface, and my (and Mark's) > concern about missing sound wave on analog part of hardware in the > beginning of playback. Without the information, users of this codec > driver will be puzzled in their hardware test. I can easily imagine > that. > > For example, 5 phases of word select clock can be calculated: > - 0.113379 msec at 44.1 kHz > - 0.104167 msec at 48.0 kHz > - 0.026042 msec at 192.0 kHz > > Kernel's timer service doesn't work by such accurate expiration > time. At the best, 1 msec or more. On the other hand, typical drivers > for any serial sound interface starts data transmission after a > callback of .trigger. > > Essentially, kernel's timer service is designed for 'rough' expiration > to release system resources, such as socket buffer for any internet > protocol. It surely guarantees timer expiration, but not for its > accuracy. > > But Mark Brown approved your idea under a certain compromise, due to > current design of ALSA SoC part. The part includes no guarantee of > timing to enable clocks on serial sound lines between .hw_params and > .trigger, in my understanding. Thank you for your comment, yes, it should be indicated log or comment. I noticed other approach in response to your remarks. I will try to use it. Best regards --- Kuninori Morimoto _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
