I have a desktop machine with Gigabyte GA-770TA-UD3 motherboard, and up until now I’ve been unable to suspend it in Linux. It would suspend, then immediately wake up. If I ran, e.g., ‘pm-suspend’ from the command line, I would see this in /var/log/messages:

[   92.192894] PM: Syncing filesystems … done.
[   92.268839] PM: Preparing system for mem sleep
[   92.268847] Freezing user space processes … (elapsed 4.87 seconds) done.
[   97.140091] Freezing remaining freezable tasks … (elapsed 0.00 seconds) done.
[   97.140218] PM: Entering mem sleep
[   97.140228] Suspending console(s) (use no_console_suspend to debug)
[   97.140386] pm_op(): usb_dev_suspend+0x0/0x20 returns -2
[   97.140388] PM: Device usb8 failed to suspend: error -2
[   97.140390] PM: Some devices failed to suspend
[   97.140421] PM: resume of devices complete after 0.029 msecs
[   97.690227] PM: resume devices took 0.550 seconds
[   97.690247] PM: Finishing wakeup.
[   97.690250] Restarting tasks … done.

The motherboard has a usb3 hub in it – thanks to this post I figured out it was the xhci module that was holding up the suspend.  I did ‘sudo modprobe -r xhci’ and confirmed I could suspend.

To “solve” it permanently, I’ll put a file in /etc/pm/config.d with the line:

SUSPEND_MODULES=“xhci”

 Whee.

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