[alsa-devel] [PATCH] ALSA: hda - hdmi: Fix channel map switch not taking effect

[Takashi Iwai]

At Tue, 15 Oct 2013 19:22:00 +0300,
Anssi Hannula wrote:
> 
> 15.10.2013 18:32, Takashi Iwai kirjoitti:
> > At Mon, 07 Oct 2013 15:09:15 +0200,
> > Takashi Iwai wrote:
> >>
> >> At Mon, 07 Oct 2013 15:45:09 +0300,
> >> Anssi Hannula wrote:
> >>>
> >>> Takashi Iwai kirjoitti 2013-10-07 13:43:
> >>>> At Mon, 07 Oct 2013 13:31:17 +0300,
> >>>> Anssi Hannula wrote:
> >>>>
> >>>> Takashi Iwai kirjoitti 2013-10-07 10:48:
> >>>>> At Wed,  2 Oct 2013 21:13:32 +0300,
> >>>>> Anssi Hannula wrote:
> >>>>>
> >>>>> Currently hdmi_setup_audio_infoframe() reprograms the HDA channel
> >>>>> mapping only when the infoframe is not up-to-date or the non-PCM flag
> >>>>> has changed.
> >>>>>
> >>>>> However, when just the channel map has been changed, the infoframe may
> >>>>> still be up-to-date and non-PCM flag may not have changed, so the new
> >>>>> channel map is not actually programmed into the HDA codec.
> >>>>>
> >>>>> Notably, this failing case is also always triggered when the device is
> >>>>> already in a prepared state and a new channel map is configured while
> >>>>> changing only the channel positions (for example, plain
> >>>>> "speaker-test -c2 -m FR,FL").
> >>>>>
> >>>>> Fix that by keeping track of the last programmed channel map and making
> >>>>> hdmi_setup_audio_infoframe() always update the hardware mapping if the
> >>>>> channel map has changed.
> >>>>>
> >>>>> Hmm, maybe it's easier (and safer) to remove the check and always call
> >>>>> hdmi_setup_channel_mapping()?  Of course, the drawback is the
> >>>>> unnecessary verbs, but it's not too much.
> >>>>
> >>>> Easier, yes. I don't really have that good of an idea how big of a 
> >>>> delay
> >>>> do 8 write verbs cause, so I'll rely on your judgment :)
> >>>>
> >>>> I guess I could replace the writes with read-and-write-if-differs 
> >>>> cycles
> >>>> when I add the set_slot ops for ATI/AMD, since it seems to be used for
> >>>> other similar cases (like channel count)?
> >>>>
> >>>> Well, this would result in more cost, as read requires a sync.
> >>>
> >>> Hmm, so why does e.g. converter channel count set-up use that, then?
> >>
> >> It can be optimized as well :)
> >>
> >>>> If any, we can use the cached write/update.  But this assumes that the
> >>>> hardware never clears the value by some operation internally.
> >>>
> >>> It should not, but better be safe than sorry here (at least for stable) 
> >>> :)
> >>>
> >>>>> Signed-off-by: Anssi Hannula <anssi.hannula at iki.fi>
> >>>>> Cc: <stable at vger.kernel.org>
> >>>>> ---
> >>>>>
> >>>>> BTW, is there some mechanism preventing hdmi_chmap_ctl_put() to be
> >>>>> called
> >>>>> at the same time with generic_hdmi_playback_pcm_prepare() that I didn't
> >>>>> see with a quick look?
> >>>>> Both of them call hdmi_setup_audio_infoframe() which is not
> >>>>> thread-safe.
> >>>>>
> >>>>> Yeah, we need to introduce a mutex there.
> >>>>
> >>>> I guess hdmi_present_sense() is the same, as it can also call
> >>>> hdmi_setup_audio_infoframe()?
> >>>>
> >>>> Hm, looking at the code, we have already pin_eld->lock in
> >>>> hdmi_present_sense().  This can be used in other places, too.
> >>>
> >>> Well, hdmi_setup_audio_infoframe() is non-threadsafe for other reasons 
> >>> than
> >>> eld as well (e.g. write verbs to hw), though, so it might be a bit 
> >>> confusing
> >>> as-is. Better move/rename the lock if we end up using it? Or not?
> >>
> >> Yeah, it'd make sense.
> >>
> >>>> (And pin_eld->monitor_present change at the beginning of
> >>>> hdmi_present_sense() should be protected in the mutex, too...)
> >>>>
> >>>> BTW, shouldn't hdmi_present_sense() call hdmi_setup_audio_infoframe()
> >>>> always
> >>>> when eld_changed is true? hdmi_setup_audio_infoframe() does not do its
> >>>> stuff if !monitor_present, so if one starts playback before plugging 
> >>>> in,
> >>>> the channel mappings etc will never be set even when plug-in happens
> >>>> (from what I can see, that is -  did not test yet).
> >>>>
> >>>> Well, there is such a call but currently specific to Haswell because
> >>>> it hasn't been tested for others.  Maybe we can simply get rid of
> >>>> is_haswell() check there.
> >>>
> >>> OK, will test later and provide a patch if it works as expected.
> >>
> >> Thanks.
> > 
> > [dropped stable from Cc]
> > 
> > Anssi, is the lock fix/cleanup patch ready?
> > 
> > I already have patche to extend mutex lock over other places and
> > move it into per_pin, but if you have already similar patches, I'll
> > take yours, hopefully together with other fixes.
> 
> Nope, haven't had the time to work on it yet (my excuse is that I was at
> XBMC DevCon last weekend :) ).
> 
> So feel free to apply yours and I'll work on top of that (at some point
> later this week I guess).

Anssi, do you have the merge-ready version of AMD HDMI fix patches?
Since 3.13 merge window will be opened soon, I'd like to merge such
big (and good) things now if possible.


Takashi