4K @ 60Hz over HDMI 2.0 not working with AMDGPU-DAL

Submitted by Dillon Dixon

Assigned to Default DRI bug account

Link to original bug (#98333)

Description

So this is regarding AMDGPU DAL as it currently exists in https://cgit.freedesktop.org/~agd5f/linux/log/?h=amd-staging-4.7, which from my understanding contains the most up-to-date public-facing iteration of the DAL patch.

So I have an HDMI 2.0 4K 60 Hz monitor (Vizio D40u-D1) as my main display connected to an XFX RX 480. I'm using a kernel compiled from the branch listed above.

Now the issue I'm having is that I'm stuck at 30 Hz. The RX 480 is capable of driving this monitor at 60 Hz @ 4K, which works under Windows. Trying to switch to 60 Hz either results in no signal, or just 30 Hz again.

I had the same issue in the past with the proprietary Linux Nvidia drivers on a 960 GTX I used to own, and after several months, the devs there were able to figure out what the issue is, describe it in a forum post, and get a fix in. See here: https://devtalk.nvidia.com/default/topic/939971/linux/4k-60hz-works-in-windows-not-in-linux/

So what I'm hoping is that a similar fix would work in DAL.

I can provide logs on request (not sure to log right now).

Thanks!