XPS 15, Linux no longer resumes from sleep w/ Bios 1.2.10

Same here, coupled with frequent reboots on resume.

You can revert to 1.2, which will solve the problem.

Sorry to hear about that.

Has anyone tried the same BIOS update on a Precision 5510 DE ? 

Sorry, wasn't clear.  That is on a 5510.

Same happening here. Have you tried to connect an external HDMI monitor? On my computer just the monitor was not showing anything.

Monkeypatch to resume without external monitor: If you can enter your session (typing the password and enter), and then pressing F12 (to pump up the brightness to full setting), your display might come back in full brightness and keep on that setting (until reboot!).

I've come back to BIOS 1.2.0 to fix this issue.

I'm having the same issues, it seems that something goes wrong with the brightness control upon resuming from suspend.  At times I will resume with an illuminated screen, but I won't be able to dim it until hitting the lowest brightness setting at which the backlight will turn off.  At other times, it resumes with the backlight completely off and I can sometimes turn it on by raising the brightness to maximum but not always.  More irritating is that since updating my BIOS (on a Precision 5510), the brightness hotkeys no longer consistently function.  While I can continue to adjust my brightness on the POST screen and bootloader, once the linux kernel loads, the keys stop seeming to produce any output.  I'm not sure how I can re-enable their functionality.  Has anyone else experienced this?

Edit:  The hotkeys seem to resume functioning if I reboot while disconnected from the ac adapter.

My brightness keys work (only after logging in) but my screen is always at full brightness when I turn it on or reboot (I never use suspend).

Hi vgough,

same problem here.

Just two questions:

- I've deleted my old copy of bios 1.2.0. Where I can find a copy of it?

- Your link to the optimization tips is broken, Could you help me to reach it in any way?

This page has lots of useful information for tuning Ubuntu on an XPS: 

http://wiki.yobi.be/wiki/Laptop_Dell_XPS_15

I found the older bios releases on dell's site here: http://downloads.dell.com/published/pages/xps-15-9550-laptop.html

Reverting back to version 1.2.0 fixed the backlight problems for me.

So, is this the right place to notify Dell about this issue? Is Dell aware of it?

I have no idea.  They've certainly never acknowledged it here.

The official channel for getting support with Precision systems (including those running Ubuntu) is through Dell ProSupport. You can reach out to them from http://www.dell.com/support/incidents-online/us/en/19/contactus/Dynamic

That said, I've escalated this regression to Canonical.

Won't help.  This also happens with kernel 4.7 running Arch.

Your link doesn't work.

Very disappointed that something reported in a support forum doesn't get tracked.  

To echo gregbunk, this appears to be a regression in the most recent BIOS update rather than in the OS (unless, of course, Canonical is involved with the BIOS which seems unlikely).  I've seen this same behavior in Gentoo using multiple kernel versions.