[RESOLVED] HDMI Stops working after unplug/replug

Hi all,

Running Debian Unstable and recently I’ve been having an issue where HDMI stops working if the monitor is unplugged then later plugged back in (or if the laptop is plugged into a different HDMI monitor). xrandr shows the relevant output as “disconnected” no matter what I do. Physically removing the HDMI expansion card and reinstalling it makes everything come good.

FYI I have the HDMI expansion card without the power saving mod (gen 2?). I’ve been meaning to do the mod, and have the right equipment, but just haven’t found the time. I haven’t explicitly tried upgrading the HDMI expansion card firmware (I believe you need to do the bodge wire mod first), but I have run fwupdmgr - my understanding is that this only updates e.g. UEFI and not expansion cards.

I’m thinking this is probably due to some update I’ve installed recently, perhaps some bug in a newer kernel? I plan to hunt around more, but just wondering if anyone is having the same issue.

Hi @Lauren ,

I see you’re running Debian Unstable, when in doubt always test this first with our current supported distros Ubuntu 22.04 Live and Fedora 39 Live, if it works there then yes it might have something to do with more bleeding edge packages.

Is yours an AMD board? Are you considering the full output of xrandr, or just the port the external monitor previously showed up on? If you unplug, use xrandr to disable the port (--off) even though it’s marked disconnected, and then replug, does that resolve it?

I had a possibly-similar issue (Gentoo, AMD), and wound up working around it with an EDID emulator to fake the monitor always being present, then telling the kernel to always use/assume the TV’s original EDID… but I would be very interested to know about cases where plugging/unplugging was working without issue.

Is yours an AMD board?

No, Intel 12th gen.

Are you considering the full output of xrandr , or just the port the external monitor previously showed up on?

The full output. All outputs show “disconnected” except the output for the internal display.

Looking at the Linux Kernel Mailing List it does seem that some work was being done on HDMI in the past few weeks. Most likely there was a bug at some point that has now been patched, and whenever Debian devs release a new kernel build the problem will magically resolve itself. In the meantime, regards what Loell said, yes, I’ll try to USB boot a supported Linux version to confirm that this isn’t hardware or firmware related. Obviously I don’t expect support from anyone for my decision to run an experimental distro version :grin: but just curious as to whether anyone else is doing the same and has come across the issue (and/or for visibility if someone else does have this problem in future).

This is resolved - as of today the HDMI expansion card no longer seems to stop responding when the cable is unplugged. I’m now on Linux 6.7.9, so most likely there was a regression in the Debian version of Linux 6.7.7 that has subsequently been fixed.

1 Like