On Sat, 31 Dec 2022 13:10:18 +0100, Jaroslav Kysela wrote: > > On 31. 12. 22 12:38, Ruud van Asseldonk wrote: > > Hi all, > > > > I bisected this and identified e4ea77f8e53f9accb9371fba34c189d0447ecce0 > > (ALSA: usb-audio: Always apply the hw constraints for implicit fb sync) > > as the first commit where it is no longer possible to change the sample > > rate. On the parent commit, my sample program successfully changes the > > sample rate from 44100 Hz to 96000 Hz, but on e4ea77f8e53f9, the second > > call to snd_pcm_hw_params fails. > > There is an easy workaround - call snd_pcm_hw_free() between the > params setup. This call ensure that the sync ep is freed. I can just > confirm that this > problem is only for USB hw with the implicit feedback (tested with 6.0.11 kernel). > > I will try to debug this when I find a little free time. Perhaps, > Takashi may have a straight idea, what's wrong. When only one stream > is used, this hw_params call should succeed, too. The patch like below might help (note: totally untested). My wild guess is that it's an internal stream start for the implicit fb case at prepare without actually starting a PCM stream, and it wasn't stopped properly before the second hw_params call. Takashi -- 8< -- --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -525,6 +525,8 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream, if (snd_usb_endpoint_compatible(chip, subs->data_endpoint, fmt, hw_params)) goto unlock; + if (stop_endpoints(subs, false)) + sync_pending_stops(subs); close_endpoints(chip, subs); }
