Note to self: dr3 not supported on X270: solved
Fri, 12 Dec 2025 10:33:26 +0100
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The CPU with integrated GPU on my X270 is an

Intel(R) Core(TM) i5-6300U CPU @ 2.40GHz 2.13/3.00GHz

Intel HD Graphics 520 @ 1.00 GHz (Skylake gen 9)

It doesn't support DR3 in xorg's default configuration.

I had a deeper look and tried enabling GuC in the i915 module.
GuC=3 is rejected, but Guc=2 enables HuC.

1) edit /etc/modprobe.d/i915.conf
2) add: options i915 enable_guc=2
3) save, then run mkinitcpio
4) doas mkinitcpio -P
5) reboot

doas dmesg | grep -i -e 'huc'

HuC is enabled.

xdpyinfo | grep -i "DRI"

Both DRI2 and DRI 3 are now enabled, and mpv no longer sends 
warnings about DRI3

glxgears now runs sychronized to the 60hz vertical refresh rate:
300 frames in 5.0 seconds = 59.995 FPS

https://wiki.archlinux.org/title/Intel_graphics

I also set some xorg options to false to improve performance 
and compatibility - until I see a need to change these.

/etc/11/xorg.conf.d/10-intel.conf

Section "Device"
     Indentifier "Intel"
     Driver      "intel"
     BusID       "PCI:0:2:0"
     Option      "Accel"        "true"
     Option      "AccelMethod"  "SNA"
     Option      "DRI"          "3"
     Option      "TearFree"        "false"
     Option      "TripleBuffer"    "false"
     Option      "SwapbuffersWait" "false"
EndSection
 
Section "Module"
     Load        "dri3"
EndSection


Voila.

␌