Lenovo 100w Gen 4 (ADL-N, ALC257, 17aa:3802): internal mic silent/noise, NHLT table not found #6005

System

• Machine: Lenovo 100w Gen 4 (DMI system version: Lenovo 100w Gen 4)
• CPU/platform: Intel Alder Lake-N (HDA controller 8086:54c8)
• Codec: Realtek ALC257, subsystem 17aa:3802
• OS: [Zorin OS version] (Ubuntu 24.04 base)
• Kernel: 7.0.0-38-generic
• firmware-sof-signed: [version from dpkg output]
• BIOS: [version / date], no newer BIOS available via fwupd

Problem

The internal microphone does not work at all on Linux. The speakers work.

Findings

1. dmesg with the SOF driver: "NHLT table not found" and
   "DMICs detected in NHLT tables: 0". There is no NHLT table in
   /sys/firmware/acpi/tables/. Firmware: ABI 3:22:1, Kernel ABI 3:23:1.
2. Codec pin config: Node 0x12 "Internal Mic", Pin Default 0x90a60130
   ([Fixed] Mic at Int, Conn = Digital). Node 0x19 is the external
   jack mic.
3. Default boot (legacy snd_hda_intel, snd_intel_dspcfg left at default):
   only "HDA Analog" capture device. Recording with arecord -D hw:0,0
   gives noise only; playback of a recording made while speaking
   contains only noise. All ALSA controls are unmuted and at maximum
   (Capture 100%, Internal Mic Boost 3/3).
4. With snd_intel_dspcfg.dsp_driver=3 (SOF): same ALC257 analog path
   (hw:0,0), noise only. Measured with sox, trimming the first 0.5 s:
   silence RMS 0.017452 vs speech RMS 0.017455 (no difference).
5. SOF + dmic_num=2 (forced via modprobe option): DMIC and DMIC16kHz
   capture devices appear (hw:0,6, hw:0,7, topology
   sof-hda-generic-2ch.tplg), but the recorded value is a constant
   -0.001526 both in silence and when speaking, so the DMIC path
   delivers no data.
6. The 3.5 mm jack is untested / [tested with headset: result].

Expected

Internal microphone works, or the machine is added to a quirk/DMI table
with the correct DMIC configuration.

Question

Since the firmware does not provide an NHLT table, is there a known
DMIC configuration (number of mics, PDM pins) or a quirk for this
machine? I can test patches, module parameters or an injected NHLT.

Attached

• alsa-info.txt
• dmesg-audio.txt