[PTL/HURACAN] SoundWire bus clash/parity isolated to link 3 causes speaker dropout — Dell XPS 14 DA14260, 4x CS35L57 + CS42L45

[vitillo]

Environment

• Laptop: Dell XPS 14 DA14260 ("HURACAN"), SKU 0DB9, board 0VRKYR, BIOS 1.8.2
• CPU: Intel Core Ultra X7 358H (Panther Lake)
• Audio PCI: 8086:e428 (subsys 1028:0db9), driver sof-audio-pci-intel-ptl
• OS: Omarchy 4.0.2
• Kernel: linux-ptl 7.1.8.arch1-2 (7.1.8-arch1-2-ptl)
• Firmware: sof-firmware 2025.12.2-1 (ADSPFW + booted 2.14.1.1),
  linux-firmware(-cirrus) 20260810-2, alsa-ucm-conf 1.2.16.1-1
• Userspace: pipewire 1:1.6.8-1, wireplumber 0.5.15-1

Topology: No SoundWire machine driver found for the ACPI-reported configuration → function-topology fallback:
sof-sdca-jack-id0 / sof-sdca-mic-id4 / sof-sdca-2amp-id2 /
sof-hdmi-pcm5-id5, all ABI 3:29:1 vs Kernel ABI 3:23:1.

Slaves (all Attached):

• link 0: sdw:0:0:01fa:4245:01 (CS42L45, sdca_class, devnum 6)
• link 2: sdw:0:2:01fa:3557:01:2 (devnum 2, tuning spkid1-l2u2) +
  sdw:0:2:01fa:3557:01:3 (devnum 1, tuning spkid0-l2u3)
• link 3: sdw:0:3:01fa:3557:01:0 (devnum 2, tuning spkid0-l3u0) +
  sdw:0:3:01fa:3557:01:1 (devnum 1, tuning spkid0-l3u1)
• All 4 amps: CS35L57 Rev B2 OTP1, fw:4.2.1, DSP v4.5.9,
  tuning Dell_Hurracan14.
• Aux devices present: soundwire_intel.link.0/.2/.3 (no link.1).
• Masters 0/2/3 report identical DisCo clocks: 4.8/9.6 MHz, row 50,
  col 4, 48 kHz, err_threshold 0, clk_stop_modes 0x3.

What's wrong?

Intermittent dropout of one speaker channel during normal desktop use.
PipeWire sink volumes/balance are unchanged (L/R 100%/0dB, balance 0.00,
no mute) before/during/after — this looks like a bus-level fault, not mixing.

Repro

No isolated trigger yet — happens roughly daily under normal desktop use.
Tighter dmesg -w ↔ audible-dropout correlation in progress
(journalctl -k -f | grep -iE "clash|parity" + speaker-test -c2 -D hw:0,2).

Log: 25/25 events on link.3 over 7 days, zero on link.2/link.0

12x control clash, 11x data clash, 2x parity:

Sep 02 21:20:47 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for data word
Sep 02 21:23:24 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 02 21:23:24 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for data word
Sep 02 21:24:22 hyperion kernel: soundwire_intel soundwire_intel.link.3: Parity error
Sep 02 21:24:22 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 02 21:24:22 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for data word
Sep 02 21:28:41 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 02 21:28:41 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for data word
Sep 02 21:29:38 hyperion kernel: soundwire_intel soundwire_intel.link.3: Parity error
Sep 02 21:29:38 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 02 21:30:31 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 02 21:30:31 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for data word
Sep 02 21:34:00 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 02 21:34:00 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for data word
Sep 03 12:59:58 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 03 13:01:17 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 03 13:04:54 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for data word
Sep 03 13:12:50 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 03 16:21:35 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 03 16:21:35 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for data word
Sep 03 16:26:12 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for data word
Sep 03 16:26:46 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 03 16:26:46 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for data word
Sep 03 16:45:14 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for control word
Sep 03 16:45:14 hyperion kernel: soundwire_intel soundwire_intel.link.3: Bus clash for data word

Notes / asks

• I checked drivers/soundwire/intel_auxdevice.c:sdw_master_read_intel_prop():
  SDW_MASTER_QUIRKS_CLEAR_INITIAL_{CLASH,PARITY} are already set
  unconditionally, so this is not the boot-time spurious-INT case from
  ~5.13 — these are runtime sdw_cdns_irq() reports, which only log.
• How should I distinguish slave-bonkers vs SI vs Master-timing/PM on PTL?
  Useful next captures: per-slave SCP_INT1 at fault time, error counting +
  bus reset, debugfs intel-registers/cdns-registers for link 2 vs 3,
  PM/clock-stop isolation?
• Happy to provide alsa-info (with dmesg), acpidump/DSDT, dyndbg
  (soundwire_bus, soundwire_cadence, soundwire_intel,
  snd_soc_sof_sdw), and dropout-correlated traces on request.