Clearfog[Pro] TDM Interface use as SPDIF

Heisath · February 11, 2018

Hi,

the ClearfogPro has a so called TDM interface. This also contains a pin for spdif and i2s. I have been trying to get it to work for some time,

but unfortunately it is not included in the solidrun image nor is there any documentation on it from their side.

As far as I figured it out the TDM is for some external VoIP Cards, and I2S is a sound protocol between sounddevices.
So I would like to use SPDIF to stream some audio to my amplifier.

I checked in the function and hardware specs for the Armada 388 (88F6828) and the schematics of the clearfogpro and it seems that pin mpp51 is would be used for spdif.

This pin also does not collide with any other usages (according to pin map) and is currently not referenced in the device tree.

I attached the relevant parts of the pinlist etc to this post.

Has anyone got the spdif working or has an idea on how I might go on?

I assume there needs to be a device tree entry to configure the internal registers for spdif output and at the same time provide the armbian with a sound device for alsa...

Greetings,

count-doku

zador.blood.stained · February 12, 2018

There needs to be a compatible kernel driver for this audio interface first. Currently mainline has the driver and DT entries (link) for Armada 370 and it may be incompatible with 38x.

Looks like TDM and audio controller were supported in the old 3.10.x kernel: https://github.com/SolidRun/linux-marvell/blob/linux-3.10.y-clearfog/arch/arm/boot/dts/armada-38x.dtsi

and looks like 370 and 38x are not exactly compatible: https://github.com/SolidRun/linux-marvell/commits/linux-3.10.y-clearfog/sound/soc and especially https://github.com/SolidRun/linux-marvell/commit/cfb2ef2cc1c062699cd594018ab9aeecbf39f9bd#diff-84901b12477cc9f68341ae510d4bee2a