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lp_us_tickers test: fix `increment test` for slow boards 

Increment test proves that ticker counter is incremented by one.
This is done indirectly for high frequency counters where it is impossible to read 'value' and 'value + 1' in two successive ticker reads.
This check is done indirectly by counting ticker ticks elapsed during execution of N cycles of empty while loop. Unfortunately on slow boards with fast tickers like NRF51_DK(16 MHz CPU/1MHz hf ticker) it is possible that for the same N cycles measured number of elapsed ticks in two successive calls is greater than 1. This patch provides fix for such case - measure operation is repeated with the same number of cycles.
pull/7009/head
Przemyslaw Stekiel 2018-02-27 14:01:22 +01:00 committed by Bartek Szatkowski
parent a92ff94904
commit 0ecf58f51c
1 changed files with 23 additions and 4 deletions
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25
TESTS/mbed_hal/common_tickers/main.cpp
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@ -46,13 +46,15 @@ volatile int intFlag = 0;
const ticker_interface_t* intf;
unsigned int ticker_overflow_delta;
/* Auxiliary function to count ticker ticks elapsed during execution of N cycles of empty while loop.
* Parameter <step> is used to disable compiler optimisation. */
uint32_t count_ticks(uint32_t cycles, uint32_t step)
{
register uint32_t reg_cycles = cycles;
const ticker_info_t* p_ticker_info = intf->get_info();
const uint32_t max_count = ((1 << p_ticker_info->bits) - 1);
core_util_critical_section_enter();
const uint32_t start = intf->read();
@ -65,7 +67,10 @@ uint32_t count_ticks(uint32_t cycles, uint32_t step)
core_util_critical_section_exit();
return (stop - start);
/* Handle overflow - overflow protection may not work in this case. */
uint32_t diff = (start <= stop) ? (stop - start) : (uint32_t)(max_count - start + stop);
return (diff);
}
void ticker_event_handler_stub(const ticker_data_t * const ticker)
@ -302,9 +307,23 @@ void ticker_increment_test(void)
uint32_t next_tick_count = base_tick_count;
uint32_t inc_val = 0;
while (next_tick_count == base_tick_count) {
while (inc_val < 100) {
next_tick_count = count_ticks(NUM_OF_CYCLES + inc_val, 1);
if (next_tick_count == base_tick_count) {
/* Same tick count, so increase num of cycles. */
inc_val++;
} else {
/* It is possible that the difference between base and next
* tick count on some platforms is greater that 1, in this case we need
* to repeat counting with the same number of cycles.
* In cases if difference is exactly 1 we can exit the loop.
*/
if (next_tick_count - base_tick_count == 1 ||
base_tick_count - next_tick_count == 1) {
break;
}
}
}
/* Since we are here we know that next_tick_count != base_tick_count.