At Tue, 2 Nov 2010 10:02:49 +0100 (CET), Jaroslav Kysela wrote: > > On Tue, 2 Nov 2010, Takashi Iwai wrote: > > > At Tue, 2 Nov 2010 09:26:48 +0100 (CET), > > Jaroslav Kysela wrote: > >> > >> On Tue, 2 Nov 2010, Takashi Iwai wrote: > >> > >>> At Tue, 2 Nov 2010 09:17:33 +0100 (CET), > >>> Jaroslav Kysela wrote: > >>>> > >>>> On Tue, 2 Nov 2010, Takashi Iwai wrote: > >>>> > >>>>> At Mon, 1 Nov 2010 17:12:53 -0500, > >>>>> Pierre-Louis Bossart wrote: > >>>>>> > >>>>>> Merged and cleaned patch based on earlier patches posted > >>>>>> on alsa-devel by Clemens Ladisch <clemens@xxxxxxxxxx> and > >>>>>> Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxx> > >>>>>> > >>>>>> This patch disables period interrupts which are not > >>>>>> needed when the application relies on a system timer > >>>>>> to wake-up and refill the ring buffer. The behavior of > >>>>>> the driver is left unchanged, and interrupts are only > >>>>>> disabled if the application requests this configuration. > >>>>>> The behavior in case of underruns is slightly different, > >>>>>> instead of being detected during the period interrupts the > >>>>>> underruns are detected when the application calls > >>>>>> snd_pcm_update_avail, which in turns forces a refresh of the > >>>>>> hw pointer and shows the buffer is empty. > >>>>> > >>>>> So, this silently assumes that the applications do call > >>>>> snd_pcm_update_avail() appropriately at the right timing? > >>>>> If so, any sense to check XRUN in the driver at all...? > >>>>> > >>>>> And, even more, any sense to report the incremental position by this > >>>>> approach? The only reliable information in this case is the offset in > >>>>> the ring buffer. The linear position as the current ALSA API provides > >>>>> isn't guaranteed without the period irq. > >>>> > >>>> We can detect the buffer size crossing using jiffies, but I agree, it's > >>>> something which should be added to the patch to not break hw_ptr in > >>>> case when the application does not call the update function in time. > >>>> We have both values in runtime->hw_ptr_jiffies and > >>>> runtime->hw_ptr_buffer_jiffies. > >>> > >>> But I thought this patch also disabled the jiffies check? > >> > >> These values are not related only to the debug jiffies check. I'm using > >> these values also to detect the double irq acks which were discovered > >> recently. > > > > Ah, OK, I overlooked it. > > > >>> I feel that some bottom-line check is needed if we keep the linear > >>> position over the buffer size even without the period irq. > >>> If the app doesn't care, OK fine, the driver shouldn't care, too. > >>> But then it doesn't make sense to keep the linear position, either. > >> > >> But if we can keep the linear position using the light-weight jiffies > >> check, it's probably OK to keep it rather than changing the hw_ptr > >> behaviour. > > > > Well, but the point of the patch is to avoid wakeups as much as > > possible. The jiffies-check adds an unconditional wakeup for each > > buffer size, thus it's against the purpose of the patch. > > I don't see any wakeup. The CPU is woken up. This is to be avoided. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel