k_busy_wait vs Trustzone

[Nico_ID]

Dear All,

I'm willing to set up a project based on the nRF9160, using the Trustzone. Thus, I have two firmwares, two zephyrs that will run in Secure and Non Secure memories as defined by SPU configuration. My problem appears when in both firmwares I have to use the "k_busy_wait" or "k_sleep".

In fact, Zephyr during it's early initialization phases, has to configure the RTC and CLOCK peripherals. So when the Secure Firmware starts first, no problem. I can use the mentioned delay functions. Before switching to Non Secure Firmware, I must configure those two peripherals as Non Secure (in SPU config) for the Non Secure Zephyr initialization to succeed. If I don't it crashes as the RTC and CLOCK peripherals won't be configurable.
So I do configure them a Non Secure, but my issue is that if I call back a Secure service from Non Secure (using veneers), a Secure service that use "k_sleep" or "k_busy_wait", it will crash as the RTC / CLOCK peripheral has changed its state to Non Sec in SPU.

How should I manage such issue ?
I tried the configure the RTC / CLOCK with SPU_PERIPHID_PERM_SECUREMAPPING_Split but it does not work neither.

Any hint ?

Thanks.

[Nico_ID]

EDIT : 

I just realized that SECUREMAPPING field in SPU PERIPHID[n].PERM is read only !

So the RTC/CLOCK can't be shared among both Zephyrs.

I have to find a way to start the second Zephyr without RTC/CLOCK to keep that feature in Secure.

[Håkon Alseth]

That is true. The kernel will use RTC1 (see here) as the clock source, and it does not have an option to select the RTC instance at this time. I've had a chat with the developers, and they are aware of this scenario, and will look into it in the future.

 

Kind regards,

Håkon