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Time measurement using Performance Monitors Register on Cortex-A72

Chanh

Hi all,

I am writing the Bare Metal program on ARM Cortex-A72. I follow some examples to configure the Performance Monitors Registers to do timing measurement.

The initializing step is as below:

Set bit EN, ER, CR (bit 0, 2, 3) of PMUSERENR_EL0 to 1

Set bit E, C, P (bit 0, 1, 2) of PMCR_EL0 to 1

Set bit C (bit 31) of PMCNTENSET_EL0 to 1

After initalize, I read back the register value is:

  • PMUSERENR_EL0 : 0xD
  • PMCR_EL0 : 0x41023001
  • PMCNTENSET_EL0 : 0x80000000

However, when I read the counter by reading the register PMCCNTR_EL0, I always get 0.

May I know any wrong with the setting? Or can you suggest any way to resolve it? Thanks a lot for your help

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