On Tue, 16 Jul 2019 05:57:51 +0200, Channaiah Vanitha (RBEI/ECF3) wrote: > > Hello Takashi-san, > > Can you please reply your feedback for below mail chain. > > Best regards, > Vanitha Channaiah > RBEI/ECF3 > > _____________________________________________ > From: Channaiah Vanitha (RBEI/ECF3) > Sent: Tuesday, June 18, 2019 4:44 AM > To: 'Takashi Iwai' <tiwai@xxxxxxx> > Cc: alsa-devel@xxxxxxxxxxxxxxxx; Wischer Timo (ADITG/ESS) <twischer@xxxxxxxxxxxxxx> > Subject: RE: [PATCH v2 4/6] pcm: direct: Round up of slave_app_ptr pointer if buffer size is less than 2 period size. > > > Hello Takashi-san, > > Firstly, very sorry for the late reply. > > > The current condition was chosen because otherwise it'll cause > > underrun errors. If the round down is needed for avoiding errors, it > > should be changed, yes. Otherwise, it needs a careful evaluation. > > > If buffer=2*period, the chance to slip the update is quite high unless you align the start. And the instability with 2xperiod is the very reason we've added this hack at the beginning. > > If this is the case, current condition would also solve under run errors for the condition buffer=2*period+1frame. > For, buffer=2*period+1frame, snd_pcm_wait() is waiting for more than a period and this could lead to xruns. > The chance to slip the condition is more in case of buffer=2*period-1frame. Because, after first write (one period write), avail is less than one period by 1 frame. It has to wait until next DMA interrupt. There is more chance of xruns. > In case of buffer=2*period, after first write (one period write) avail is still one period size and there is less chance of xruns. > > > In anyway, the description in the patch doesn't match with the change. > > Please update it to fit with the actual change if we still need to > > take this change inevitably. > > For buffer>=2*period, round down of slave pointers and for buffer=2*period-1frame, round up of slave pointers will avoid xruns. > Which otherwise causes snd_pcm_wait() to block for more than a period time and leads to xruns. Hmm, it's still not clear at all. Please repost the patch with a more elaborated and correct description that matches with the code change. thanks, Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
