alsaucm (part of the alsa-utils package) to set up the sound card:
ALSA_CONFIG_UCM=/opt/alsa/ucm alsaucm -c rk3399-gru-sound set _verb HiFi
Note that the port will display as "Headphones" despite using the speakers. When paired with pulseaudio and pulseaudio-alsa, be aware that the full volume range is addressed through levels 0-9 of the Master volume control. Levels 10-100 provide no additional gain.
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