Comment 14 for bug 1465766

I have a similar issue on Debian 9 (Stretch) on a Lenovo X1 Carbon 6th Gen laptop.

DMI: LENOVO 20KHCTO1WW/20KHCTO1WW, BIOS N23ET63W (1.38 ) 04/20/2019

The built-in speaker volume is limited to about 20% even if the volume is set at 100%.

The sound card is a ALC285 handled by the snd_hda_intel driver.

On my kernel (4.9.0-9-amd64 #1 SMP Debian 4.9.168-1+deb9u2 (2019-05-13)), I managed to find this work-around which addresses the low volume issue:

Edit /etc/modprobe.d/alsa-base.conf

add the following line:

options snd-hda-intel model=nofixup

After modprobe -r/modprobe of the snd_hda_intel module (or reboot), the volume works fine.

Hopefully this can help others facing this open issue as well.

Here is the output of lspci -vvv for the sound card:

00:1f.3 Audio device: Intel Corporation Device 9d71 (rev 21) (prog-if 80)
 Subsystem: Lenovo Device 225c
 Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
 Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
 Latency: 64
 Interrupt: pin A routed to IRQ 125
 Region 0: Memory at 2ffb018000 (64-bit, non-prefetchable) [size=16K]
 Region 4: Memory at 2ffb000000 (64-bit, non-prefetchable) [size=64K]
 Capabilities: [50] Power Management version 3
  Flags: PMEClk- DSI- D1- D2- AuxCurrent=55mA PME(D0-,D1-,D2-,D3hot+,D3cold+)
  Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-
 Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit+
  Address: 00000000fee00278 Data: 0000
 Kernel driver in use: snd_hda_intel
 Kernel modules: snd_hda_intel, snd_soc_skl