How long does it take to wake up from from WFI once an interrupt occurs?
What system parameters does the answer depend on?
What's turned off in the CPU (and elsewhere) while WFI is underway?
I'm using NXP i.MXRT1050 (Cortex M7) and I'm experiencing what seems to be longer than expected wake up time.
Now, that's some more info ;-)
4.7ms is a lot. I'd try to do a measurement with systick timer as well. The delay might be related to the external interrupt. Do you "simply" use WFI or do you also enter WAIT mode?
One idea is, that it is related to PLL locking, but the data sheet states it is below 2250 cycles of the 24MHz reference clock (edit: ~100us).
Anyway, interesting that NXP does not give any hint how long it takes to leave the different power-saving modes :(