DoxyGen: remind users to enable trace before using PMU
Add some notes to remind users to enable trace via:
CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
before using PMU.
This is originally mentioned in
'Application Note
Armv8.1-M Performance Monitoring User Guide'
@@ -15,6 +15,9 @@ unsigned int l1_dcache_miss_count = 0;
unsigned int instructions_retired_count = 0;
// Enable the PMU
+// Note: Before using the PMU, software needs to ensure
+// that trace is enabled via the Debug Exception Monitor Control Register, DEMCR:
+// CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
ARM_PMU_Enable();
