Reverse Prime issue

gee · 2017-04-09 07:52:36

Hello,

I have a RadeonHD 280X that I use for both audio and video hdmi output, but I recently moved from the radeon module to the amdgpu one to be able to use radv. Having done that I had to give up, among other things, on hdmi audio.

To workaround that problem, I am using my intel iGPU's HDMI to output the audio, which works okayish for my needs. I've followed the wiki on Reverse Prime to set it up. Unfortunately if I specify a correct driver for the intel device, either intel or modesetting, Plasma has some sort of issues and either doesn't start, or starts but with only the background image displayed and no panel or anything working. Specifying a wrong driver works around that but that seems dirty. Also, when I come back to my computer after a long time of no use, with the screen and the receiver off during that time, sometimes the audio doesn't work anymore and since I don't use the proper xorg driver I don't see my intel iGPU in xrandr and have no choice but to restart the machine.

All in all, how can best I fix the situation?

Thank you!

Lone_Wolf · 2017-04-09 12:02:20

This sounds like you want the radeon 280x to do the rendering, but use the intel card to do hdmi audio .

I don't know know how to achieve that, but all reverse prime does is allow your intel integrated card to use the outputs on the 280x .

Do your hdmi screens have sound inputs ?

gee · 2017-04-09 12:07:01

Lone_Wolf wrote:

This sounds like you want the radeon 280x to do the rendering, but use the intel card to do hdmi audio .

Correct, and that's what I get with my setup right now.
But having to put a wrong driver is a bit weird, and prevents me from fixing stuff later on...

Lone_Wolf wrote:

I don't know know how to achieve that, but all reverse prime does is allow your intel integrated card to use the outputs on the 280x .

To be fair, maybe I don't need it in my setup, that's just the only way I found it to work, but I have little experience with dual GPU setups.
Maybe I'm not even using it since I cannot use the xrandr line with a proper driver for both...

Lone_Wolf wrote:

Do your hdmi screens have sound inputs ?

I'm using a TV and an amp so yes
Alas my amp does not seem to support two hdmi at the same time, so my GPU is directly hooked to my TV and the iGPU is hooked to the receiver, that means no OSD anymore...

Thank you!

Last edited by gee (2017-04-09 12:08:14)

Lone_Wolf · 2017-04-09 12:55:02

How about a hardware based solution ?

I'm pretty sure the amdgpu kernel module has good Display Port support, and that also includes video and audio .

Maybe a Display Port to HDMI converter cable will work ?

https://www.startech.com/AV/Displayport … r~DP2HDMI2

EDIT :

Or you could try the linux-amd-staging kernel that has the DC/DAL code not yet accepted in linux-mainline .
It's available from lordheavy' unofficial mesa-git repo , https://wiki.archlinux.org/index.php/Un … s#mesa-git

Last edited by Lone_Wolf (2017-04-09 12:59:21)

gee · 2017-04-09 13:01:02

That may very well work, but I'm not really interested in a hardware based-solution though.
Are you sure that there is valid audio for SI cards for that purpose though?

Thanks!

Lone_Wolf · 2017-04-10 09:58:53

Are you sure that there is valid audio for SI cards for that purpose though?

Can't guarantee it will work, but those converters are relatively cheap.
There is another way though, check my edit in post #4.

gee · 2017-04-10 10:22:00

DC does not help me as it's not for SI cards.

The thing is my current setup somewhat works, I just have to restart the computer when I lose audio, which is annoying, but still fairly quick.
Earlier I was able to rmmod and modprobe back some modules to get the audio back, but it probably took longer to run these 2 commands ( well mostly the 1st one) than just restarting

Last edited by gee (2017-04-10 11:55:59)

Lone_Wolf · 2017-04-10 10:52:40

I'm almost certain DC/DAL are intended for cards using amdgpu kernel module , aka gcn cards.

check lspci -k , if it shows both radeon & amdgpu as kernel modules for your card you can choose between those 2.
NOTE : kernel modules are NOT the same as the modules listed in xorg log .

gee · 2017-04-10 11:53:25

I am only on amdgpu (both kernel and xorg), but DC is definitely not for GCN 1.0 cards, I'm not sure about 1.1, I think it's 1.2+ plus for now.
(I had a quick chat with Alex about that a few weeks ago when asking for status of audio support for GCN 1 cards and future implementation)

Arch Linux

#1 2017-04-09 07:52:36

Reverse Prime issue

#2 2017-04-09 12:02:20

Re: Reverse Prime issue

#3 2017-04-09 12:07:01

Re: Reverse Prime issue

#4 2017-04-09 12:55:02

Re: Reverse Prime issue

#5 2017-04-09 13:01:02

Re: Reverse Prime issue

#6 2017-04-10 09:58:53

Re: Reverse Prime issue

#7 2017-04-10 10:22:00

Re: Reverse Prime issue

#8 2017-04-10 10:52:40

Re: Reverse Prime issue

#9 2017-04-10 11:53:25

Re: Reverse Prime issue

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