Re: ASoC: tas2783-sdw: no stereo channel split for two mono amps -> mono output (AMD ACP SoundWire, ASUS ProArt PX13)

Hi Antoine,

Confirmed on a second machine: ASUS ProArt PX13 HN7306EAC (Ryzen AI MAX+
395), Ubuntu 26.04, 7.2-rc4 based kernel, same two TAS2783 at unique_id
0x8 / 0xB plus RT721 on SoundWire link 1.

Rather than judging by ear, I used the per-amp mixer controls, which
makes the result unambiguous. Both amps at full scale ('tas2783-1/-2 Amp
Volume' = 20, 'Speaker Volume' = 200), all four 'Left/Right Spk[2]
Switch' on:

  speaker-test -Dpipewire -c2 -s1 (left channel only)
    - audible
    - 'tas2783-2 Speaker Volume' = 0  -> complete silence
    - 'tas2783-1 Speaker Volume' = 0  -> no audible change

  speaker-test -Dpipewire -c2 -s2 (right channel only)
    - silent, with both amps unmuted at full scale

So exactly your picture: one amp (tas2783-2) renders audio and it renders
the *left* channel, the other amp contributes nothing, and the right
channel is never reproduced. Both amps do load their own per-address
blob here (1714-1-8.bin / 1714-1-B.bin, via the fallback naming path
after the 0x-prefixed names miss), so this is not a case of the wrong
configuration being downloaded.

On the "proper mechanism" question: a good part of the plumbing already
exists, and it does not need unique_id at all.

 - The machine layer already knows which amp is which. In
   sound/soc/sdw_utils/soc_sdw_ti_amp.c, asoc_sdw_ti_spk_rtd_init() maps
   the component name prefix to a speaker widget: tas2783-1 -> "Left
   Spk", tas2783-2 -> "Right Spk", tas2783-3/-4 -> "Left/Right Spk2".
   That is where the four 'Left/Right Spk[2] Switch' controls on this
   board come from.

 - asoc_sdw_hw_params() (sound/soc/sdw_utils/soc_sdw_utils.c) fills
   dai_link->ch_maps, but for playback it deliberately hands every codec
   the full mask ("Identical data will be sent to all codecs in
   playback"), leaving the per-amp channel selection to the amp itself.
   acp-sdw-legacy-mach, which drives this board, uses both.

So the driver could derive the channel from the same prefix index the
DAPM routing already uses, or from its entry in dai_link->ch_maps,
instead of hard-coding SoundWire addresses.

Which raises the question for TI: on TAS2783 is the channel selection
meant to come from the per-device .bin (in which case it is evidently
not taking effect on this board), or is the driver expected to program a
per-amp channel mask? Depending on the answer, either the firmware
description or tas_sdw_hw_params() needs fixing - and in the latter case
the amp's channel should come from the machine-level mapping rather than
from unique_id, which as you say is board-specific.

Happy to test patches on this hardware; I can also collect register
dumps from both amps if that helps.

Thanks,
Andrey