[BUG] sof-lnl-rt722-l0.tplg only exposes 2ch — 4-speaker Dell Lunar Lake systems missing half their speakers

[PythonTilk]

Describe the bug

On the Dell Inspiron 16 Plus 2-in-1 (Lunar Lake, RT722 SDCA), only 2 of 4 physical
speakers produce sound under Linux. The RT722 SmartAmp (SDCA function 4) is correctly
detected with 4 independent output clusters (0x21, 0x22, 0x23, 0x24) as reported by
ACPI, indicating a quad-speaker hardware configuration. However, the loaded topology
sof-lnl-rt722-l0.tplg only configures a 2-channel stereo speaker path
(hw:sofsoundwire,2, rt722 FU06 FU, values=2). The two additional speaker channels are
never initialized, leaving ~half the speakers silent.

All 4 speakers work correctly in Windows via the Waves MaxxAudio Pro DSP. No
sof-lnl-rt722-l0-4ch.tplg exists in sof-bin through v2025.12, unlike the cs42l43 codec
which has both sof-lnl-cs42l43-l0-2ch.tplg and sof-lnl-cs42l43-l0-4ch.tplg.

What was tried: Verified the SmartAmp ACPI device:23 status=15 (fully functional),
confirmed 4 SDCA clusters, checked all available LNL topology files in sof-bin — no 4ch
RT722 variant exists for LNL.

To Reproduce

1. Boot on affected hardware (Dell Inspiron 16 Plus 2-in-1, Lunar Lake, RT722)
2. Play audio through internal speakers
3. Physically touch/check each speaker — only 2 respond
4. Verify: amixer -c sofsoundwire cget name='rt722 FU06 Playback Volume' shows values=2
   (2-channel only)
5. Verify: pactl list sinks | grep -A3 Speaker shows audio.channels = "2"

Reproduction Rate

100% — persistent across all boots.

Expected behavior

All 4 speakers produce audio, requiring a sof-lnl-rt722-l0-4ch.tplg topology that
configures all 4 SmartAmp output clusters (analogous to the existing
sof-ptl-rt722-4ch.tplg for Panther Lake).

Impact

Significant annoyance — sound quality and volume are noticeably degraded compared to
Windows due to half the speaker array being inactive.

Environment

1. Kernel: 7.0.3-arch1-2 / SOF firmware: 2025.12.2 (DSP fw version: 2.14.1.1)
2. Topology: intel/sof-ipc4-tplg/sof-lnl-rt722-l0.tplg
3. Platform: Intel Lunar Lake-M (sof-audio-pci-intel-lnl, PCI 0000:00:1f.3)

Console output

kernel: acpi device:20: SDCA function UAJ (type 6) at 0x1
kernel: acpi device:21: SDCA function SmartMic (type 3) at 0x2
kernel: acpi device:22: SDCA function HID (type 10) at 0x3
kernel: acpi device:23: SDCA function SmartAmp (type 1) at 0x4
kernel: sof-audio-pci-intel-lnl 0000:00:1f.3: loading topology:
intel/sof-ipc4-tplg/sof-lnl-rt722-l0.tplg
kernel: sof-audio-pci-intel-lnl 0000:00:1f.3: Booted firmware version: 2.14.1.1

$ amixer -c sofsoundwire cget name='rt722 FU06 Playback Volume'
numid=5,iface=MIXER,name='rt722 FU06 Playback Volume'
; type=INTEGER,access=rw---R--,values=2,min=0,max=87,step=0
: values=60,60

$ cat /sys/bus/acpi/devices/device:23/status
15
$ ls /sys/bus/acpi/devices/device:23/mipi-sdca-cluster-id-*
Shows clusters: 0x11, 0x21, 0x22, 0x23, 0x24, 0x31, 0x41, 0x42, 0x51

[PythonTilk]

Update: topology is likely not the root cause

After further investigation, I compared the speaker parameters across all RT722
topology variants:

• sof-ptl-rt722 (2ch) and sof-ptl-rt722-4ch differ only in DMIC parameters (NUM_DMICS,
  PDM1_MIC_*). The speaker path is identical in both — same NUM_SDW_AMP_LINKS=1, same
  SDW_SPK_STREAM=Playback-SmartAmp, same SDW_AMP_FEEDBACK=false.

The "4ch" in existing topology variants refers to 4-channel microphone capture, not
4-channel speaker playback. A new topology file alone would not fix the speaker issue.

Revised hypothesis: The RT722 SDCA SmartAmp (function 4, ACPI device:23) has 4
independent output clusters (0x21–0x24), each with 2 channels. The snd_soc_rt722_sdca
driver may only be initializing/enabling 2 of the 4 amplifier stages. The fix likely
needs to be in the RT722 SDCA driver — specifically ensuring all 4 amp instances are
powered on and receiving signal from the stereo input stream.

Verified: PipeWire exposes only 2 ports (monitor_FL, monitor_FR) for the Speaker sink,
and aplay -L shows no surround/4.0 device — ruling out UCM hiding channels.

[shumingfan]

@PythonTilk The RT722 SPK function only supports 2 channels.
Could you provide the alsa-info?
We’d like to understand how that machine is supporting 4-channel speaker output.

[PythonTilk]

@shumingfan
https://alsa-project.org/db/?f=7b5412c08ac2398d716d96c5f9c74908e280cc9a
only 2-channel stereo is exposed. The machine has 4 physical speakers (2 tweeters + 2 woofers per side based on the Dell spec), but only one stereo output is visible in Linux.

[shumingfan]

@PythonTilk
I checked this model on the Dell website.
https://www.dell.com/en-us/shop/dell-laptops/dell-16-plus-2-in-1-laptop/spd/dell-db06250-2-in-1-laptop

It shows the following audio specification:

Audio and Speakers

Stereo speakers with Realtek ALC3329 Audio Controller, 2.5W x 2 = 5W total peak

Could you confirm again, or is there any information that tells you it has a 4-channel speaker?

[PythonTilk]

@shumingfan
thanks for checking. After investigating further, I can confirm you're right — the RT722 SPK function on this machine is 2-channel only. The audio quality gap with Windows is purely a DSP/tuning problem, not a channel configuration issue. Closing this — the RT722 is working as intended.
This was my bad i js assumend channels would equal speakers.