Can't suspend Debian machine: wakes up immediately after sleep (“PM: Device usb1 failed to suspend async”)

Question

Since I installed the latest Debian updates yesterday (udev, systemd, ...) I can't put my Debian 9/KDE machine to sleep. It wakes up immediately after suspending (systemctl suspend).

/var/log/syslog has the following:

..Stopping disk
parport_pc 00:01: disabled
e1000e: EEE TX LPI TIMER: 00000011
dpm_run_callback(): usb_dev_suspend+0x0/0x20 [usbcore] returns -16
PM: Device usb1 failed to suspend async: error -16
PM: Some devices failed to suspend, or early wake event detected
parport_pc 00:01: activated
..Starting disk
..
rtc_cmos 00:07: System wakeup disabled by ACPI

There were also some other messages at other tries such as a wlan-related "driver in IPS". But no matter what I try I always get the exact same message:

PM: Device usb1 failed to suspend async: error -16

What I tried so far

• Removing my wlan driver with sudo rmmod, sudo modprobe -r and sudo dkms remove. Couldn't put it to sleep after doing that. Also the module always gets loaded again after rebooting after "successfully" removing it (it's also not shown in lsmod anymore). I have reinstalled it with dkms now.
• Disconnecting all USB devices except of my keyboard to suspend the machine and disconnecting all USB devices except of my mouse to suspend the machine and immediately disconnecting the keyboard/mouse after suspending it.

Any other ideas what I should try? I find it strange that it displays that usb error even though all usb devices are disconnected.

Answer 1

The issue was an internal card reader which apparently was connected via usb as well.
This seems to be related to: https://bugzilla.kernel.org/show_bug.cgi?id=201997
Did not find out what "usb1" was. lsusb still shows the exact same devices as before.