Re: tstile lockups - side note

[Martin Husemann <martin%duskware.de@localhost>]

This needs an audio exper to look at it:

The snapper interrupt spin mutex is passed out to the audio system
via snapper_get_locks().

Then in audiosetinfo() we do
(http://nxr.netbsd.org/xref/src/sys/dev/audio.c#3890):

                mutex_enter(sc->sc_intr_lock);
                init_error = audio_initbufs(sc);
                if (init_error) goto err;   
                if (sc->sc_pr.blksize != oldpblksize ||
                    sc->sc_rr.blksize != oldrblksize ||
                    sc->sc_pustream != oldpus ||
                    sc->sc_rustream != oldrus)
                        audio_calcwater(sc);
                if ((sc->sc_mode & AUMODE_PLAY) &&
                    pbus && !sc->sc_pbus)
                        init_error = audiostartp(sc);
                if (!init_error &&
                    (sc->sc_mode & AUMODE_RECORD) &&
                    rbus && !sc->sc_rbus)
                        init_error = audiostartr(sc);
        err:
                mutex_exit(sc->sc_intr_lock);

so audiostartr() is called with the devices interrupt lock held (which
is also asserted there). Then via hw_if->trigger_input we come to
snapper_trigger_input() -> snapper_set_rate() and then try to set
the volume via tas3004_write() - which does an iic transaction, and boom
we go. As Uebayashi-san mentions, this is a no go in interrupt context.

Now starting recording/playback should not need to do volume
adjustements. I suppose hw->commit_settings()
(http://nxr.netbsd.org/xref/src/sys/dev/audio.c#3878) should already do
that, and is called without the interrupt lock held.

Martin