I have witnessed unexpected reboots on WP7609 modules. The same module may unexpectedly reboot several times a day, then be stable for >3 days before unexpectedly rebooting again. Initially I assumed it was a custom application crashing, however all custom applications have been removed (AT!RMARESET, SPK rollback to R12, swiflash -r, clean FW install using downloaded SPK package) and the problem persists.
I have witnessed the issue on FW releases:
I have witnessed the issue on HW:
- Custom hardware w/ 3A 3.8V regulator.
- mangOH Red w/ 2.1A USB power supply.
I have tested the 3.8V rail to the module on the custom hardware, and see no voltage droop.
The issue only seems to happen when connected to LTE. Reboots have not been witnessed when connected to UMTS, however more testing is required to confirm.
The output from the serial console at the time of the crash is as follows:
[ 1931.348787] Fatal error on the modem.
[ 1931.351455] modem subsystem failure reason: lte_rrc_sib.c:1270:Assert extra_time < 2570000 failed: .
[ 1931.360853] M-Notify: General: 8
[ 1931.466459] Kernel panic - not syncing: subsys-restart: Resetting the SoC - modem crashed.
[ 1931.473750] CPU: 0 PID: 2683 Comm: kworker/0:2 Not tainted 3.18.122 #2
[ 1931.480220] Workqueue: events device_restart_work_hdlr
[ 1931.485352]  (unwind_backtrace) from  (show_stack+0x10/0x14)
[ 1931.493065]  (show_stack) from  (panic+0x90/0x1f4)
[ 1931.499920]  (panic) from  (device_restart_work_hdlr+0x38/0x3C)
[ 1931.507908]  (device_restart_work_hdlr) from  (process_one_work+0x198/0x2e4)
[ 1931.517019]  (process_one_work) from  (worker_thread+0x2e0/0x3bc)
[ 1931.525177]  (worker_thread) from  (kthread+0xc8/0xd4)
[ 1931.532387]  (kthread) from  (ret_from_fork+0x14/0x3c)
[ 1931.539590] cpr_panic_callback: apc_corner: [corner:2, fuse_corner:2] = 1062500 uV
[ 1931.547313] Rebooting in 5 seconds…
[ 1931.573549] Going down for restart now
[ 1931.577058] reboot: trigger wdog bite
[ 1931.580079] Causing a watchdog bite!
Is this a modem (firmware) instability issue? Is there a fix?