LG C4 OLED - FRL training fails with "sink does not support FRL" #35

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1. xerrni commented on Apr 16, 2026

   

   xerrni

   on Apr 16, 2026

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   try: #23 (comment)

   This is my general fix for LG tv's. should work.

   👍React with 👍1Reacted by Michael Piepgras Neergaard
2. piepgras commented on Apr 21, 2026

   

   piepgras

   on Apr 21, 2026

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   try: #23 (comment)

   This is my general fix for LG tv's. should work.

   Gave it a quick whirl. No luck sadly, I'll look into it soon.
3. piepgras commented on Apr 21, 2026

   

   piepgras

   on Apr 21, 2026

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   Tried getting it to work.
   I manually applied all three changes (sink version retry, FLT_UPDATE quirk, and DFM-selected rate bypass) directly to link_frl_training.c, since the line numbers have shifted.

   After manually editing the source and confirming the changes compiled in, the kernel is missing critical modules for btrfs-based systems (btrfs, usbhid, overlay, crypto_lz4), maybe this is expected and I didn't do my homework. mkinitcpio fails and the initramfs is incomplete, so I can't fully boot to test.

   What I can confirm tho:
   manufacturer_id 0x6D1E is correctly detected for the LG C4
   The LG C4 reports as "LG TV SSCR2" with product_id 82CD
   I suppose the LG C4 must behave differently from the B9 used in @xerrni 's patch.. different webOS version (10.3.0-25), different panel generation.

   I'll keep cracking. Happy to provide additional info :)
4. xerrni commented on Apr 22, 2026

   

   xerrni

   on Apr 22, 2026

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   0005-FIX.patch

   AUR package already takes care of correctly creating kernel config. Do not manually create one.
   Just put my patch to correct place. I use btrfs and it works so it defenetly applies correct changes to kernel config file.

   https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=linux-mkopec-git#n122

   https://aur.archlinux.org/packages/linux-mkopec-git

   So to do it step by step once again:

   1. Install linux-mkopec-git package: yay -Suy linux-mkopec-git or using other aur helper.
      This step will create /etc/linux-mkopec-git/ directory and required config files:

   l -R /etc/linux-mkopec-git/
   /etc/linux-mkopec-git/:
   total 20K
   drwxr-xr-x 1 root root   38 kwi  8 15:09 .
   drwxr-xr-x 1 root root 4,9K kwi 22 11:40 ..
   -rw-r--r-- 1 root root  126 kwi  8 15:02 config
   drwxr-xr-x 1 root root  328 kwi  8 15:09 patches
   -rw-r--r-- 1 root root  546 kwi  8 15:02 remote
   
   /etc/linux-mkopec-git/patches:
   total 40K
   drwxr-xr-x 1 root   root    328 kwi  8 15:09 .
   drwxr-xr-x 1 root   root     38 kwi  8 15:09 ..
   -rw-r--r-- 1 USER USER 3,3K kwi  8 15:01 0005-FIX.patch
   -rw-r--r-- 1 root   root    357 kwi  8 14:51 patches
   

   2. download patch file 0005-FIX.patch
   3. Place it in /etc/linux-mkopec-git/patches directory as show above
   4. edit /etc/linux-mkopec-git/config file:

   # List here the patches' filename to be applied in the correct order.
   # All patches need to be placed in this directory and have the .patch name
   # extension.
   #
   # PATCHES=(
   #   '0001-foo.patch'
   #   '0002-bar.patch'
   #   ...
   # )
   
   PATCHES=(
   '0005-FIX.patch'
   )

   5. Rebuild kernel with this patch
      yay -S linux-mkopec-git linux-mkopec-git-headers --rebuild

   6. Make sure that you boot to correct kernel -- edit your boot configuration file, I use systemd-boot,

   my config:
   /boot/loader/entries/arch_amd.conf

   title Arch Linux amd 120HZ version
   linux //vmlinuz-linux-mkopec-git
   initrd /amd-ucode.img
   initrd /initramfs-linux-mkopec-git.img

   If you still insist on Your manual way, link to config file from aur repo:

   https://aur.archlinux.org/cgit/aur.git/tree/config?h=linux-mkopec-git

   It has btrfs turned on https://aur.archlinux.org/cgit/aur.git/tree/config?h=linux-mkopec-git#n11062
   Remember that its not advised to change kernel config by hand, rather use tool included in kernel source code, by executing make menuconfig Why ? because of e.g. dependencies.
5. xerrni commented on Apr 22, 2026

   

   xerrni

   on Apr 22, 2026

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   FIY I worked with grok to create this patch, feel free to do use is as base conversation. but remember one thing, he does not understand how to create good patches, so It's best to just get his diff and create patch by hand, how to do so:

   # navigate to linux source e.g.
   pushd ~/.cache/yay/linux-mkopec-git/src/linux-mkopec
   # apply diff changes by hand - time consuming but ensures that it will work since grok is unable to create good .diff .patch file
   
   git add -u
   git commit -m "my patch"
   git format-patch -n HEAD^ # this creates real patch that will be usable
   git checkout HEAD~1 # get rid of your changes
   cp ./0001-my_path_sth.patch /etc/linux-mkopec-git/patches/0005-FIX.patch
   yay -S linux-mkopec-git linux-mkopec-git-headers --rebuild
   systemctl reboot
6. piepgras commented on Apr 22, 2026

   

   piepgras

   on Apr 22, 2026

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   There we go! 2160p@144hz, 10b 4L12 hdr10 with vrr.

   Haven't done any testing yet, i seem to have some flickering, but that just might be hyprland and my current config.

   Thanks for the assist @xerrni !
7. xerrni commented on Apr 23, 2026

   

   xerrni

   on Apr 23, 2026

   Last edited by xerrni

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   My pleasure, that's what GNU/Linux community is for.
   Test for couple days and report back. Also did You just apply my patch or did you change sth, write about it so other people could also benefit from that.

   also watch for logs using:

   sudo dmesg --follow
   # or
   sudo dmesg --follow-new

   We need to create robust solution that could be upstream-ed, so anyone could benefit.

   FIY I tested on kde and some full screen games.

   👍React with 👍1Reacted by Daniel
8. piepgras commented on Apr 29, 2026

   

   piepgras

   on Apr 29, 2026

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   Been running great since we got it working, 0 issues I've noticed, my first reboot since the kernel switch was today.

   I applied the patch just like you said.

   Only issue I've encountered is that my secondary display needs to be disconnected at boot.
   As for VRR flickering, running games in fullscreen fixes it.

   Anything else I can do? Would very much like to see this go upstream :)

   Log from fresh boot:
   dmesg.log
9. jarrard commented on May 2, 2026

   

   jarrard

   on May 2, 2026

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   Sadly tried this patchset on my AMD NUC with 780M GPU and it causes display to be stuck at 60hz max.

   It did however get the colorspace correct at 10bit etc... but yeah looks like it just straight up looses the hz rates above that. Guessing DSC can't activate for some reason and its not dropping to 420 color to compensate.

   Shame. This is one area where Windows is just massively dominant in atm, being able to display any colorspace and settings on any screen, but under Linux I've hit so many issues getting the correct settings to work.
   Don't even get my started on Intel iGPU support under Linux, its even worse, lol