[alsa-devel] 2 speakers are assigned to the same DAC, this can't support 4.0/2.1 channles

[Takashi Iwai]

At Wed, 10 Jun 2015 12:19:58 +0800,
hwang4 wrote:
> 
> 
> 
> On 2015年06月09日 21:26, Hui Wang wrote:
> > On 06/09/2015 07:51 PM, Takashi Iwai wrote:
> >> At Tue, 09 Jun 2015 17:38:33 +0800,
> >> hwang4 wrote:
> >>> I am trying to enable the subwoofer speaker on a HP laptop, on this
> >>> machine, there are two speakers and one headphone, but the BIOS verb
> >>> only enabled one speaker(nid 0xd) and one headphone(nid 0xb), I need
> >>> to use quirk in the kernel driver to configure the second speaker
> >>> (subwoofer speaker, nid 0x10). Under current alsa driver, the
> >>> headphone will be assigned a dac (nid 0x13) and the 2 speakers will
> >>> be assigned a dac (nid 0x14), this assignment is not good since 2
> >>> speakers share the same dac, this means 2 speakers can't work
> >>> at the same time to support 4.0/2.1 channels.
> >>>
> >>> On another Dell machine with realtek codec, there are also 2 speakers,
> >>> 1 headphone and 2 dacs, on this machine, 1 speaker and 1 headphone are
> >>> assigned
> >>> 1 dac, and the other speaker is assigned another dac, so there is no
> >>> problem for this machine to support 4.0/2.1 channels.
> >>>
> >>> Through debugging, I found on Dell machine, the speaker nid only has
> >>> one connection to dac (hardwired), so when driver assign dac to it, the
> >>> map_single() can successfully assign the each dac to the 2 speakers
> >>> respectively.
> >>> But on that HP machine, the speaker has multiple connections for 
> >>> dac, the
> >>> map_single() can't work for this machine.
> >>>
> >>>
> >>> The alsa-info.txt for that HP machine is at
> >>> http://pastebin.ubuntu.com/11667947/
> >>> The alsa-info.txt for that Dell machine is at
> >>> http://pastebin.ubuntu.com/11667982/
> >>>
> >>> To fix this problem, I can use the quirk in the driver to make the
> >>> speaker have
> >>> only one connection for dac or do some change in the hda_generic.c like
> >>> below, in
> >>> your opinion, which one is better or probably you have a different idea
> >>> to fix this problem?
> >>>
> >>> diff --git a/sound/pci/hda/hda_generic.c b/sound/pci/hda/hda_generic.c
> >>> index ac0db16..8194ff1 100644
> >>> --- a/sound/pci/hda/hda_generic.c
> >>> +++ b/sound/pci/hda/hda_generic.c
> >>> @@ -1363,6 +1363,7 @@ static int try_assign_dacs(struct hda_codec
> >>> *codec, int num_outs,
> >>>                                   dac = try_dac(codec,
> >>> get_primary_out(codec, i), pin);
> >>>                           if (!dac)
> >>>                                   dac = try_dac(codec, dacs[0], pin);
> >>>                           if (!dac)
> >>>                                   dac = try_dac(codec,
> >>> get_primary_out(codec, i), pin);
> >>>                           if (dac) {
> >>> @@ -1762,6 +1763,12 @@ static int fill_and_eval_dacs(struct hda_codec
> >>> *codec,
> >>>                   if (err < 0)
> >>>                           return err;
> >>>                   badness += err;
> >>> +               /* if there are 2 speakers and both of them are 
> >>> assigned
> >>> to the same dac,
> >>> +                  we need to increase the badness for this situation,
> >>> because in this situation
> >>> +                  the 2 speakers can't work together to support 
> >>> 4.0/2.1
> >>> channels */
> >>> +               if (cfg->speaker_outs == 2 && err <
> >>> spec->extra_out_badness->no_dac &&
> >>> +                   spec->multiout.extra_out_nid[1] == 0)
> >>> +                       badness += spec->extra_out_badness->no_dac;
> >> This doesn't look like the correct place to add badness for the
> >> missing surround speaker.  This function is called for each path, so
> >> it's evaluated not only for speakers.
> >>
> >> A cleaner way would be to prepare a different badness table for the
> >> speaker, and increase the value for shared_surr.  An untested patch is
> >> below.
> > Got it, I will test it soon. Thanks.
> >
> Hi Takashi,
> 
> Your patch can fix the problem, it works very well.

OK, good to know.  I'd like to test a bit more via hda-emu whether
this gives any ill effects.  So far, this seems fixing a few other
machines, too, so it's a good thing to have in general.


Takashi