Dear community,
I'd like to measure the execution time of a computation routine on RM57L LaunchPad. I followed a PDF tutorial on "execution time measurement", used the PMU to measure the code. And I have several questions regarding the tutorial:
Q1: Could I set f_HCLK to be 330 MHz, that is, the maximum frequency?
/* -- Code Cycles / Run Time Calculations -- */
#if PMU_Cycle
cycles_PMU_code = cycles_PMU_measure - cycles_PMU_comp;
time_PMU_code = cycles_PMU_code / (f_HCLK * loop_count_max); // time_code [us], f_HCLK [MHz]
printf("Total time taken by CPU: %.2fus\n", time_PMU_code);
#endif //PMU_Cycle
I found a post related to the requirement, in which f_HCLK is only a third of the maximum frequency.
https://e2e.ti.com/support/microcontrollers/hercules/f/312/t/347072
Q2: A strange behavior of event counters: I'd like to start one selected event counter at one time,
_pmuInit_();
_pmuEnableCountersGlobal_();
_pmuResetCounters_();
_pmuSetCountEvent_(pmuCOUNTER0, PMU_CYCLE_COUNT);
_pmuStartCounters_(pmuCOUNTER0);
cycles_start = _pmuGetEventCount_(pmuCOUNTER0);
// RUN benchmark code...
_pmuStopCounters_(pmuCOUNTER0);
cycles_end = _pmuGetEventCount_(pmuCOUNTER0); // cycles_start and cycles_end are both 0!
Instead, if I start all 3 event counters at the same time, it works. Did I make a mistake in the code? I was totally lost.
Q3: In the tutorial, the event counter pmuCOUNTER0 is used to count the PMU cycles instead of PMU_CYCLE_COUNT. This method should have some benefits. For example, PMU_CYCLE_COUNT might go overflowed and reset to 0 automatically after some time?
From this perspective, pmuCOUNTER0 should better be reset each time when execution measurement starts. Correct?
volatile uint32 cycles_start, cycles_end;
/* NOTE: reset all 3 event counters 0-2 */
_pmuResetEventCounters_();
/* select CPU cycles (Event 0x11) to be counted */
_pmuSetCountEvent_(pmuCOUNTER0, PMU_CYCLE_COUNT);
_pmuStartCounters_(pmuCOUNTER0);
cycles_start = _pmuGetEventCount_(pmuCOUNTER0);
I'd like to reset only the specified event counter (pmuCOUNTER0) and keep other event counters going. Is this idea realizable in RM57? I couldn't find a function in "HL_sys_pmu.h" that resets specified event counters. Could I write an .asm file myself to do this task?
Do I have to configure the event counter once again after the reset? Must _pmuSetCountEvent_(pmuCOUNTER0, PMU_CYCLE_COUNT) be called directly after pmuResetEventCounters_(), in order to make the event counter pmuCOUNTER0 count the event "PMU cycles" after the reset?
Thanks in advance and best regards,
Honig
