Comment 81 for bug 1295267

This might also work:

https://askubuntu.com/questions/511601/how-to-make-suspend-work-without-the-screen-staying-black-afterwards

Copy and paste solution in case of linkrot:

> This is actually a simple one:

> Add pm-suspend --quirk-dpms-on to the /var/cache/pm-utils/last_known_working.quirkdb file.

> Reboot and it should work flawlessly.