Trying to get dual display on Lenovo Legion 5 Pro (6800H + RTX3060)

This is long, thanks for reading.

I have Gentoo Linux installed on a Legion 5 Pro (6800H + RTX3060). BIOS is configured for hybrid graphics.

It works great! AMDGPU driver works perfectly as the primary display. I have the RTX3060 passed through to a windows Virtual machine and it works great as well!

However, I’ve hit a snag. I want to run dual 4K Monitors on the AMDGPU. Configured as it is, the outputs from the laptop are dedicated like this:

HDMI + Back Left DP 1.4 = GTX 3060
Laptop Display + Front Left DP 1.4 = RDNA2 APU

I can’t seem to change them.

What I want is to run two external monitors from the APU and capture the HDMI output of the RTX 3060 and display it in a window. The latter works with Looking Glass, but I can’t get both DP 1.4 outputs to be controlled by the APU.

From what I’ve been reading, it may not be possible to control that port with the APU. Is that right?

There is another option. It would be cool if I could control two 4K-60 Monitors from the RTX 3060 in the Windows Virtual Machine, but for some reason, the HDMI output will only go to 4K-30 and there is no option to do YCrCb420 to double the frame rate in windows.

I was really looking forward to doing dual monitor output from the APU. Can that be made to work?

If not, is there a way to get windows to drive 4K-60 to both it’s DP 1.4 and its HDMI?

Thanks in advance.

Update: Apparently this LG monitor’s second HDMI connection cannot do 4K-60, it can only do 4K-30.

I have the 5800h + 3070 L5Pro. Assuming yours is similar (likely), there is only a MUX switch on the internal display. The external ports are wired directly to a particular GPU. On mine, both externals go to the 3070.

And, sadly, when you use the 3070 with two displays, there’s a known (1.5+ years now…NO RESPONSE FROM NVIDIA, SHAME) bug that causes X11 to basically consume an entire CPU core (and thus burn power, hurt performance, and shorten the life of your hardware).

Thanks. That means I can’t display to two externals, unless I used the nvidia GPU for X and the APU for Windows.

That stinks. I’ll have to figure out what I can do.

Any idea why I can’t get the 3060 to run two 4K displays at 60 Hz?