Dell Latitude 5480/5488: Resume failures related to AC/battery state

In our case, reboots then hang without AC, and only GRUB’s *Loading initramfs* is visible. Forcefully turning it off, and adding `maxcpus=1` to the Linux kernel command line in the GRUB menu, gets it to boot.

I have a similar problem on DELL Precision 7740 (laptop):
1) suspend
2) unplug the cord
3) try to resume : the computer does not resume, but the keyboard is lighted
4) hard reboot (by pressing the power button during several seconds)
5) at the next boot, the computer hangs just after the GRUB.

Tested on Kubuntu 18.04 (updated), and with several Kernel: 4.14, 4.15, 4.18, 5.3.

(also tested with the recent kernel 5.6-rc7 - there is the same problem)

Pinet, can you please file a new bug agains linux source package?

I have create a new bug report:
https://bugs.launchpad.net/dell-sputnik/+bug/1871491

A similar bug affects several Dell laptop models:
- Dell 5480/5488 :
https://bugs.launchpad.net/dell-sputnik/+bug/1866343
- Dell E5470 :
https://bugs.launchpad.net/dell-sputnik/+bug/1661741
(Note that the bug https://bugs.launchpad.net/dell-sputnik/+bug/1661741 is not fixed; it has been changed, by error, to fixed. Please, it will be nice if somebody can change the status to "confirmed")

We experienced this now too with a Dell Precision 3540 with dedicated AMD graphics card.

I created an issue against the Linux source package [1].

[1]: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1883065