Comment 52 for bug 1265544

I debugged a bit further on the waking from sleep issue - it actually also happens when changing modes through xrandr so not really related to waking from S3, just turning off/on the display.

The display in the UX302LG/LA needs to be run at 24-bit apparently - the current intel-gfx code (including in drm-intel-nightly) is clamping to 18bpp due to the BIOS advertising such info in the VBT (the same behavior is seen with CSM and nonCSM mode).

If you remove the clamping, then everything works (display up at boot, modesetting works, waking from sleep works)
 - you don't really need commit c26fe8e5eb34c18aa9ab60fcf4c3150663a52306 BTW, just removing the clamping to run the pipe at 24bpp fixes all the blank screen issues.

This behavior was noted on other laptops as described in the intel-gfx bug:
https://bugzilla.kernel.org/show_bug.cgi?id=59841

As you can see in the bug description above, the temporary solution that's been merged in 3.12 was this hack:
https://bugzilla.kernel.org/attachment.cgi?id=111321&action=diff

Not entirely sure why that is not working for the UX302LG/LA yet (in fact I don't see dp_get_config called at all for some reason, so the hack does not go into effect).