Ofono either crashed or busy looped with my Huawei E1552 3G modem
tried to deactivate GPRS context. The reason was that gcd->chat was
unreferenced already in setup_ppp() but the chat was still accessed
later in at_gprs_deactivate_primary().
To fix the problem, change the logic instead to suspend chat session
for PPP and resume when PPP has disconnected. Now it doesn't crash
Deactivation still doesn't work properly with Huawei E1552, and most
probably with other Huawei modems, because the modem hangs up the chat
line after PPP deactivation. This needs to be fixed separately. The
workaround is to reboot the modem, for example physically unplug and plug
it in again.
Patch has been applied, thanks.