Screen flicker/tear on mux laptop

Graphics / Linux Linux
#1

So I have a lenovo legion y740, with an i7-9750h and a 2070 max-q. I am running KDE -plasma on X11. My laptop has a MUX switch that lets me switch between:

  1. Dedicated GPU mode (laptop runs only on the nvidia card for better performance, Intel igpu is turned off, allows me to use gsync)

  2. Hybrid mode (igpu + dgpu is turned on, helps in saving battery life)

Now With proprietary drivers installed. I have no problem running on hybrid mode, everything works fine But when I go to my bios and turn on dgpu mode, arch boots but the screen starts flickering, the second there is any gpu load - more the load, the greater is the flicker.

I had a look at https://wiki.archlinux.org/title/Hybrid_graphics And only the first part of the page offers any info about laptop that HAVE a MUX switch.

So far, here are the things that i have tried with both nvidia and nvidia-dkms drivers. I am currently using dkms.

  1. Forcing full composition pipeline in nvidia server settings and running a script that enables it on start. Screen flickering persists.

  2. Changing modeset to 1.

Both of these i followed from here:

  1. Blacklisting nouveau drivers. And that too, does nothing.

Note: Windows had a similar problem back in Sept. 2020 with the release of 456.38 but that was promptly fixed through a driver update.

#2

I have the same issue with a Lenovo Legion y740 laptop and a RTX 2070 max-q. Did you ever find a solution? Seems it’s a bug with the driver, the same bug that plagued the windows driver for a couple months. Hey Nvidia, can you port the fix from the windows driver over to Linux? It’s been almost a year.

#3

I am experiencing the same issue, with any driver after version 450.119 in any Linux distro. Linking my forum post here, I found the root cause to be the Nvidia driver identifying the connection between display and gpu as DP 1.4 instead of DP 1.2 and sending higher bitrate signal on it. (Check the screenshots linked in the post).

It would be great if any developers working on Nvidia Linux drivers could take notice.

Link to the forum post

#4

Opening this after months, and glad to see that we at least know whats causing it now. The next obvious questions are can we change that connection link in the driver by ourselves or, because drivers are closed source, how do we get this across to an nvidia dev. Because the chances they stumble across our posts and actually take notice is close to zero.