RK35xx vendor kernel: missing I2C DAC drivers

[drahnreb]

Creating a bug report/issue

• [X] I have searched the existing open and closed issues

Required Information

• DietPi version | cat /boot/dietpi/.version G_DIETPI_VERSION_CORE=9 G_DIETPI_VERSION_SUB=14 G_DIETPI_VERSION_RC=2 G_GITBRANCH='master' G_GITOWNER='MichaIng' G_LIVE_PATCH_STATUS[0]='applied'

• Distro version | echo $G_DISTRO_NAME $G_RASPBIAN bookworm

• Kernel version | uname -a Linux radxazero3w 6.1.115-vendor-rk35xx #1 SMP Tue Jun 3 13:10:51 UTC 2025 aarch64 GNU/Linux

• SBC model | echo $G_HW_MODEL_NAME or (EG: RPi3) Radxa ZERO 3 (aarch64)

• Power supply used | (EG: 5V 1A RAVpower) 5V

• SD card used | (EG: SanDisk ultra) eMMC

Additional Information (if applicable)

• Software title | (EG: Nextcloud) Want to install Pimoroni Audio Amp Shield DAC. https://pinout.xyz/pinout/audio_amp_shim

• Was the software title installed freshly or updated/migrated? Fresh.

• Can this issue be replicated on a fresh installation of DietPi? Yes.

Steps to reproduce

1. Connected Shim via soldering.

2. Compiled custom device tree overlay.

3. Build codec driver MAX98357a.

4. Added as user_overlay to dietpiEnv.txt (Details here)

5. Not working - initial pop of the speaker but no sound.

Expected behaviour

• Sound

Actual behaviour

zcat /proc/config.gz | grep MAX98357
# CONFIG_SND_SOC_MAX98357A is not set

we could try with another codec (should be ok, since pimoroni is referencing hifiberry), but:

zcat /proc/config.gz | grep PCM5102A
# CONFIG_SND_SOC_PCM5102A is not set

using a dts with dummy_codec also does not work.

[MichaIng]

We can enable the respective drivers, but no guarantee that it will work, at least not without fiddling with the device tree as well (we are currently trying to get a PCM51xxA running on the Orange Pi Zero 2W, with mainline kernel), and I can only guess that Armbian does not enable them intentionally.

Generally the config is here: https://github.com/armbian/build/blob/main/config/kernel/linux-rk35xx-vendor.config#L2036 We have a workflow on our repo which builds the kernel from our fork of the Armbain build system:

• https://github.com/MichaIng/DietPi/blob/master/.github/workflows/armbian.yml
• https://github.com/MichaIng/build

I am currently busy with a lot of other things, so would take a while before I can apply those changes and generate test builds myself. I do have a Radxa ZERO 3E, but no such HAT to test it myself either.

EDIT: Ah I see you succeeded compiling the driver? And with the device tree overlay it does work? That would be a good sign of course, no real reason to not enable the driver in this case.

[drahnreb]

@MichaIng thanks for the swift reply.

Yes, I succeeded compiling the driver. The dtoverlay seems to load fine.

root@radxazero3w:/boot# lsmod | grep max98357a
snd_soc_max98357a      16384  1

root@radxazero3w:/boot# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: PimoroniAmpSHIM [Pimoroni-Amp-SHIM], device 0: fe430000.i2s-HiFi HiFi-0 [fe430000.i2s-HiFi HiFi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

I could test a test build.

[MichaIng]

I am thinking about migrating this SBC to mainline Linux, which has the driver included as module. The issues like missing HDMI output seem to be solved, at least works well on my Radxa ZERO 3E.

Just in case you want to test:

apt install linux-{image,dtb}-current-rockchip64

EDIT: Ah wait, it has CONFIG_SND_SOC_PCM5102A=m and

CONFIG_SND_SOC_MAX9759=m
CONFIG_SND_SOC_MAX9867=m
CONFIG_SND_SOC_MAX98396=m
CONFIG_SND_SOC_MAX98520=m

But not CONFIG_SND_SOC_MAX98357A. So would at least need extending the compatible value in the device tree overlay and testing.