NForce4 CK804: SPDIF passthrough not working

[apa]

It works: I have sound in the menus, from 2-channel/mp3 audio-tracks and from DD/DTS via passthrough to my receiver!

Solution (in OpenElec 4.2.0; settings on other distros would be similar):

1. Create custom asound.state in /storage/.config/ with the following contents: http://sprunge.us/SiHH
   This state-file will, among other things, unmute the appropriate mixer controls, set proper output formats, ...).
   
2. Load the above state file with the following command:
   
   Code:

   alsactl nrestore 0 -f /storage/.config/asound.state
   Rreplace the "0" with the card-number corresponding to CK804 on your system. You may want to add this command to a custom autostart.sh in /storage/.config/ so the state is restored on every boot:
   
   Code:

   #! /bin/sh
alsactl nrestore 0 -f /storage/.config/asound.state
3. Create intel8x0.conf in /storage/.config/modprobe.d/ with the following contents:
   
   Code:

   options snd-intel8x0 spdif_aclink=1
   
   I am told that this above setting depends on the specific motherboard, so this may not work for everyone: it does work on my ASUS A8N-SLI Deluxe!
   This was the final setting that solved the issue for me. I did try this setting before, but it seems that some sources on the Internet had this mis-written as "options snd-intel-8x0 spdif_aclink=1" (notice the extra dash).
   
4. In XBMC, select the SPDIF out as both the audio-device AND the passthrough device.
   
5. You'll need to reboot for these settings to have any effect.
   

If sound still doesn't work, check the front-panel audio connector on the board. It is located on the motherboard, above the blue PCI-E slot, and between the molex-connector and the back-panel audio jacks. If you don't have a front-panel audio connector attached to it, then there must be jumpers installed on either side of the 1-pin row. Failure to do so will disable the back-panel audio outputs!

There is also a timer bug on NForce4 boards (look for "acpi_use_timer_override" on Google). BIOS 1805 for the A8N-SLI Deluxe is said to fix the timer-bug (I am told other boards have been fixed through BIOS as well). If you flash that BIOS, you'll notice a message "MP-BIOS BUG 8254 timer not connected - use noapic option to boot" during boot. To resolve this issue, follow the following steps:

1. In a SSH window, issue the following command:
   
   Code:

   mount -o rw,remount /flash
   Then, do a "cd /flash".
   
2. Edit the file extlinux.conf you'll find there. It should initially look like this:
   
   Code:

   DEFAULT linux
PROMPT 0

LABEL linux
KERNEL /KERNEL
APPEND boot=LABEL=System disk=LABEL=Storage ssh quiet
   
   Append "acpi_use_timer_override" to the kernel boot parameters so the file ends up looking similar to this:
   
   
   Code:

   DEFAULT linux
PROMPT 0

LABEL linux
KERNEL /KERNEL
APPEND boot=LABEL=System disk=LABEL=Storage ssh quiet acpi_use_timer_override
3. You'll need to reboot for these settings to have any effect.
   

I want to thank the good people on the alsa-devel mailing list as well as fritsch on the #xbmc IRC channel for all their help!