Re: [ISSUE] [CLOSED] Regression in Linux5.11? 4k resolution over displayport missing.

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Closed issue by adriangoransson on void-packages repository

https://github.com/void-linux/void-packages/issues/29394

Description:
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Hi! and apologies if this is nowhere near the correct forum to ask this (where might that be?). I noticed that upon upgrading to Linux5.11 from 5.10 that I could no longer use the maximum resolution of my external monitor. I can confirm that it does work on 5.9 and 5.10 (although for 5.10 it didn't once after a point upgrade so it seems a bit flaky).
### System

* xuname:
`Void 5.11.4_1 x86_64 GenuineIntel uptodate rFFF`
* packages: I don't know what may be the culprit so here's a bunch of them!
`linux5.11-5.11.4_1` (incl. headers)
`linux-firmware-intel-20210208_2`
`intel-media-driver-20.4.5_1`
`xf86-video-intel-2.99.917.20200515_1`
The same configuration works just fine on older kernels: `linux5.10-5.10.22_1` and `linux5.9-5.9.16_1`.
* /proc/cmdline if that is helpful
`BOOT_IMAGE=/boot/vmlinuz-5.11.4_1 root=/dev/mapper/void-root ro loglevel=4 init_on_free=1 rd.lvm.vg=void rd.luks.uuid=<uuid> resume=/dev/void/swap`

### Expected behavior
Using `xrandr`, the full resolution (3840x2160) of my external monitor should be visible.
This is how it looks on linux5.10-5.10.22_1.
```sh
xrandr
# snip
DP3 connected primary 3840x2160+0+0 (normal left inverted right x axis y axis) 600mm x 340mm
   3840x2160     60.00*+
   2560x1440     59.95  
   1920x1200     59.88  
   1920x1080     60.00    60.00    50.00    59.94    24.00    23.98  
   1920x1080i    60.00    50.00    59.94
# more output modes...
```

### Actual behavior
```sh
xrandr
# snip
DP3 connected (normal left inverted right x axis y axis)
   2560x1440     59.95  
   1920x1200     59.88  
   1920x1080     60.00    60.00    50.00    59.94    24.00    23.98  
   1920x1080i    60.00    50.00    59.94  
# more output modes...
```

### Steps to reproduce the behavior
Boot Linux5.11 and try to set the monitor resolution.
I have a laptop with a Intel Tiger Lake 1165G7 processor with integrated graphics. It is connected to a Dell P2715Q with Displayport over USB-C.