Hi,

I've read https://tf-m-user-guide.trustedfirmware.org/integration_guide/non-secure_cli... and https://tf-m-user-guide.trustedfirmware.org/design_docs/software/tfm_coopera... but I'm not sure that I understand the whole system.

For example, in this scenario:

1. NSPE is running a low-priority thread which has called into the PSA API. S partition is running to do the work. 2. NS interrupt occurs. 3. NS RTOS determines that a higher-priority thread should now run.

At step 2, the S context gets stored on the S stack. I guess at step 3 the NS RTOS ISR would manipulate the stack so that it "returns" to the higher-priority NS thread rather than to the secure partition? And then sometime later when it schedules in the low-priority thread, it will return to the interrupted S partition.

So the higher-priority thread can also make a PSA API call (provided the NS RTOS is notifying TF-M of the scheduling decisions it makes)?

Thanks,

Chris Brand

Cypress Semiconductor (Canada), Inc. An Infineon Technologies Company Sr Prin Software Engr CSCA CSS ICW SW PSW 1 Chris.Brand@infineon.commailto:Chris.Brand@infineon.com

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