[Pinephone] [v20.05.1] Unable to pick up a call after suspend

Describe your issue

It appears that when resuming from a suspend, eg25-manager loses track of the modem and restarts it. When this happens when someone's calling the phone, this results in the call being hung up, and with a single ring on the PinePhone before a "missed call" notification shows up.

@a-wai on https://gitlab.com/mobian1/devices/eg25-manager/-/issues/5 has suggested that it might be because of ModemManager lacking proper support for suspend management when used with OpenRC, since the ** Message: 16:15:09.387: ModemManager object ‘/org/freedesktop/ModemManager1/Modem/1’ removed message (in the attached eg25-manager log) should've appeared before the device was suspended.

What's the expected behaviour?

Phone wakes up from suspend, rings and shows the "calling" dialog, allows the user to pick up the call.

What's the current behaviour?

Phone wakes up from suspend, and after a few seconds on the lock screen, the modem gets reset, hangs up the call (the caller receives the hangup signal - slightly faster beeps than the ring beeps) and subsequently rings for a short time.

How to reproduce your issue?

1. Wait for the phone to go into sleep, or issue: $ loginctl suspend
2. Call it from a separate device.
3. Observe as the screen turns on but nothing happens for a few second, and then you get a hang-up tone and the PinePhone rings once.

What device are you using?

pine64-pinephone v1.2a (UBPorts Edition), modem firmware EG25GGBR07A08M2G_01.002.01.002

On what postmarketOS version did you encounter the issue?

• edge (master branch)
• stable (v20.05 branch)

On what environment did you encounter the issue?

Phone environments

• Phosh
• Plasma Mobile
• Sxmo

Other

• No environment
• GNOME
• KDE Plasma
• Kodi
• MATE
• Shelli
• Sway
• Weston
• Xfce4
• fbkeyboard
• i3wm

How did you get postmarketOS image?

• from https://images.postmarketos.org
• I built it using pmbootstrap
• It was preinstalled on my device

What's the build date of the image? (in yyyy-mm-dd format)

Was able to reproduce the issue on a fresh image built yesterday, 2021-01-22.

Additional information

dmesg.log eg25manager.log