Getting audio to work on ASUS Chromebook C302CA

This guide assumes you are using up-to-date ArchLinux

Note: on kernel >= 5.4.arch1-1, module snd-soc-skl needs to be manually built by setting CONFIG_SND_SOC_INTEL_SKYLAKE=m to get audio working.

Preparation

1. On an up-to-date ChromeOS, open the terminal and copy the firmware files to somewhere convenient to use. e.g.

   sudo mkdir /mnt/stateful_partition/cros-firmware-75.0.3770.19
   sudo cp -r /lib/firmware/ /mnt/stateful_partition/cros-firmware-75.0.3770.19/

2. Download this repo and extract the files

To get audio working (with pulseaudio)

1. Copy the firmware files from ChromeOS to /lib/firmware/intel in ArchLinux. Make sure the symlinks are pointing to the correct files

   sudo cp -r cros-firmware-75.0.3770.19/lib/firmware/intel /lib/firmware/intel

   Note: as of ChromeOS 75.0.3770.19, /lib/firmware/intel/dsp_fw_release.bin should point to dsp_fw_release_v969.bin.

2. Copy dfw_sst.bin to /lib/firmware/

   sudo cp dfw_sst.bin /lib/firmware/

3. Copy Google-Cave-1.0-Cave to /usr/share/alsa/ucm/

   sudo cp -r Google-Cave-1.0-Cave /usr/share/alsa/ucm/

4. Create a symbolic link for Google-Cave-1.0-Cave folder.

   sudo ln -s /usr/share/alsa/ucm/Google-Cave-1.0-Cave/ /usr/share/alsa/ucm/sklnau8825max

5. Blacklist snd_hda_intel module by putting the following in /etc/modprobe.d/c302ca-audio.conf

   blacklist snd_hda_intel
   

6. The following steps may reduce popping sound (YMMV)

   https://wiki.archlinux.org/index.php/PulseAudio/Troubleshooting#Glitches,_skips_or_crackling https://wiki.archlinux.org/index.php/PulseAudio/Troubleshooting#Pops_when_starting_and_stopping_playback

7. Reboot and audio should be working now

Note: You may need to repeat step 1 every time the package linux-firmware gets updated.

To switch between the speaker and the headphone automatically with jack detection

The following method is just a workaround because it only works with one user. Ideally pulseaudio should take care of this. (Need more research on alsa ucm)

1. Install the acpid package

2. Put the following in /etc/acpi/events/plugheadphone

   event=jack/headphone HEADPHONE plug
   action=sudo -u YOUR_USER_NAME XDG_RUNTIME_DIR=/run/user/YOUR_USER_ID pactl set-card-profile 0 Headphone
   

   and put the following in /etc/acpi/events/unplugheadphone

   event=jack/headphone HEADPHONE unplug
   action=sudo -u YOUR_USER_NAME XDG_RUNTIME_DIR=/run/user/YOUR_USER_ID pactl set-card-profile 0 Speaker
   

   replace YOUR_USER_NAME and YOUR_USER_ID accordingly.

3. Enable and start acpid service

   sudo systemctl enable --now acpid