After a recent upgrade of the driver (and unfortunately I do not recall the old version) X always fail to start with the error both with the current and latest long term supported drivers:
[ 17.967] (EE) NVIDIA(0): DisplayPort validation failed for MetaMode "DFP-5:2560x1600"
Restarting slim (xdm manager) usually does not work either. however, if I power cycle the monitor it seems that I at times getting X going. I attached both a failed X session and on that works.
nvidia-bug-report.log.gz (87.6 KB)
ok-X.org.0.log (33.1 KB)
fail-X.org.0.log (12.4 KB)
As a workaround, try adding:
under the “Device” section of your xorg.conf for the card that’s driving that display and see if you’re able to avoid the error.
If you don’t have an /etc/X11/xorg.conf, copy and paste one the one nvidia-settings generates and add the line above accordingly.
This post has other ModeValidation options that might or might not help to fix the issue temporaily as well: https://devtalk.nvidia.com/default/topic/541455/fix-your-drivers-nvidia-hdmi-gt-165-mhz-broken-/ It’s a different issue, but perhaps you can get arround the mode validation failures by telling the driver not to autodetect a particular parameter.
Starting X with -logverbose 6 and passing the log would probably be more helpful for figuring out whats going on. The only time I have seen an error like that is when I was exceeding the pixelclock of a active DP → HDMI adapter and I was going beyond the hardware constraints (which I think it also mentioned in the log).
Funny enough the link above is my post and I doubt that
The “DisplayPort validation failed” message happens when the link between the GPU and the monitor couldn’t be trained at a sufficiently high bandwidth to handle the mode requested. Unlike the GPU’s pixel clock, the DP link is configured dynamically and is sensitive to signal integrity problems and things like loose connections or broken wires. There’s also a lot of flaky display hardware floating around; for example, I also have a monitor that sometimes starts refusing link training until it’s power-cycled.
Do you have a different DisplayPort cable you could try? Does it work more or less reliably when you hold one of the connectors at a certain angle?