On Sun, 10 Jan 2021 18:03:32 +0100, Lauri Kasanen wrote: > > On Sun, 10 Jan 2021 11:24:22 +0100 > Takashi Iwai <tiwai@xxxxxxx> wrote: > > > > At first there was no nextpos, and _pointer() always reported pos. This > > > didn't work, the core played through the audio at chipmunk speed. So > > > there must be more that I don't understand here. > > > > Try to set the periods_min=2 and the integer periods hw constraint at > > first, and change the pointer callback to return nextpos. Also, at > > the push function, set runtime->delay = period_size as well. > > When I do all this, it still causes the chipmunk speed. Several seconds > of audio gets played in 0.3s or so. Sorry if this is taking too much of > your time, I'm a bit lost here at what the alsa core is expecting. > > Printks show the following repeats: > start, period size 1024 > push, bool irq=0 > irq fired > push, bool irq=1 > pointer at 8192 > stop Hm, is the above about the result with the pointer callback returning pos, not nextpos? If so, > start, period size 1024 > push, bool irq=0 At this moment, nextpos is 1024, and it should take some time until > irq fired ... this IRQ is triggered; it must be the period time. Was the reported timing as expected? > push, bool irq=1 > pointer at 8192 If it's the first IRQ, isn't the nextpos 2048? > stop It's stopped likely because the position reported the driver is beyond the data size the application filled (XRUN). > It stops and starts again for some reason. This does not happen in the > current pos/nextpos implementation. > > > > - the DMA unit has errata if (start + len) & 0x3fff == 0x2000, this > > > must never happen > > > > Ditto. > > Can it really handle a constraint this complex? That'd be impressive. > It'd remove the memcpy need if so. The hw constraint can be just a function that filters the min/max value the driver may accept, so such a rule is possible. > > > - the audio IRQ is not a timer, it fires when the card's internal > > > buffers are empty and need immediate refill > > > > It's the current implementation, right? > > Yes, but I was wondering if a different setup would work better. The > alsa setup is a bit confusing to me still. The implementation became a bit complex due to the hardware restriction, yeah. thanks, Takashi
