[Letux-kernel] Letux/Alpha 400: small progress with sound

[H. Nikolaus Schaller]

Hi Paul,

> Am 30.04.2021 um 00:20 schrieb Paul Boddie <paul at boddie.org.uk>:
> 
> Yes, this is very strange. Although there are device tree nodes in the 3.18 
> kernel files, I don't find the corresponding drivers. There is audio support 
> in the HDMI driver, but since I use a DVI monitor, I never tried to use the 
> audio on the CI20 since the cable won't be passing on any audio signal. But I 
> imagine that there must be HDMI audio support because there was some effort to 
> get video playback working with a special version of MPlayer, as I recall.

I have looked through the 3.18 kernel and there is an "old style sound board file":

sound/soc/jz4780/ci20.c

which is compatible = "ingenic,ci20-audio"

This defines two dai links. Apparently one which is called "headphones" and one
called "hdmi". Both seem to use the jz4780-i2s. Difference is in the codecs:

dw-hdmi-audio vs. jz4780-codec.

So the hdmi audio seems to be part of a more general ci20 audio driver than
"simple-audio-card". This raises another question: should we forward port
the ci20-audio.c driver or try to make simple-audio-card work?

Anyways the codec driver can be found in sound/soc/codecs/jz4780.c

So I will replace the attempt to modify the jz4770 driver to use the one
from the 3.18 kernel...

BR,
Nikolaus