Is it possible for the nrf9160 to remove patches from the modem?

[Matt Gillespie]

We have two cases where the modem has downgraded itself from version1.3.2 to 1.3.1.

1. In the first case, due to water ingress, it appears that the reset pin has been toggled many times in rapid succession and on the next full boot, the modem has downgraded. Has it possibly erased some flash which was applied to1.3.1 (which it was originally programmed with) such as a jump table to the new patch for 1.3.2.?

2. In the second case we enabled GNSS in the modem and we received a reset where both the watchdog and system reset request flags were set. Is there some type of supervisor that could have decided to remove the patch to recover bricked devices? 

[Michal]

Hello,

I will look into it internally and get back to you, possibly not before the end of this week though.

Best regards,

Michal

[Michal]

Hello,

This can happen if the delta package is still available (i.e. hasn’t been erased after FOTA has been applied). If modem triggers reset which does not go through normal error handler then secure boot can think that FOTA update has failed and it will do the rollback operation. This is what most probably happened in these 2 cases.

There are two ways you can prevent it:

• erase the delta package once the FOTA is done OR

• by writing 1 to GPMEM3 in rpc_transport_ipc_rx_init() before nrf_modem_reset_clear() is called - Note: this is untested feature by us

Best regards,

Michal

[Matt Gillespie]

Thankyou for the answer. Can we call int nrf_modem_delta_dfu_erase(void); to erase the area once we have successfully booted after a modem upgrade?

[Michal]

According to the documentation, yes:

https://docs.nordicsemi.com/bundle/ncs-latest/page/nrfxlib/nrf_modem/doc/delta_dfu.html#erasing_the_scratch_area