tests: drivers: timer: nrf_grtc: Fix test_get_ticks

Test was occasionally failing when two types of current time
reading occurred at different system tick. In that case they
were of by one system tick and test was failing.

Signed-off-by: Krzysztof Chruściński <[email protected]>

Author: nordic-krch

tests/drivers/timer/nrf_grtc_timer/src/main.c

@@ -40,18 +40,37 @@ ZTEST(nrf_grtc_timer, test_get_ticks)
 
 	for (uint32_t i = 0; i < NUMBER_OF_TRIES; i++) {
 		/* Absolute timeout 1ms in the past */
-		t = Z_TIMEOUT_TICKS(Z_TICK_ABS(sys_clock_tick_get() - K_MSEC(1).ticks));
+		uint64_t curr_tick;
+		uint64_t curr_grtc_tick;
+		uint64_t curr_tick2;
 
-		exp_ticks = z_nrf_grtc_timer_read() - K_MSEC(1).ticks * CYC_PER_TICK;
+		do {
+			/* GRTC and system tick must be read during single system tick. */
+			curr_tick = sys_clock_tick_get();
+			curr_grtc_tick = z_nrf_grtc_timer_read();
+			curr_tick2 = sys_clock_tick_get();
+		} while (curr_tick != curr_tick2);
+
+		t = Z_TIMEOUT_TICKS(Z_TICK_ABS(curr_tick - K_MSEC(1).ticks));
+
+		exp_ticks = curr_grtc_tick - K_MSEC(1).ticks * CYC_PER_TICK;
 		ticks = z_nrf_grtc_timer_get_ticks(t);
+
 		zassert_true((ticks >= (exp_ticks - CYC_PER_TICK + 1)) &&
 				     (ticks <= (exp_ticks + GRTC_SLEW_TICKS)),
 			     "Unexpected result %" PRId64 " (expected: %" PRId64 ")", ticks,
 			     exp_ticks);
 
 		/* Absolute timeout 10ms in the future */
-		t = Z_TIMEOUT_TICKS(Z_TICK_ABS(sys_clock_tick_get() + K_MSEC(10).ticks));
-		exp_ticks = z_nrf_grtc_timer_read() + K_MSEC(10).ticks * CYC_PER_TICK;
+		do {
+			/* GRTC and system tick must be read during single system tick. */
+			curr_tick = sys_clock_tick_get();
+			curr_grtc_tick = z_nrf_grtc_timer_read();
+			curr_tick2 = sys_clock_tick_get();
+		} while (curr_tick != curr_tick2);
+
+		t = Z_TIMEOUT_TICKS(Z_TICK_ABS(curr_tick + K_MSEC(10).ticks));
+		exp_ticks = curr_grtc_tick + K_MSEC(10).ticks * CYC_PER_TICK;
 		ticks = z_nrf_grtc_timer_get_ticks(t);
 		zassert_true((ticks >= (exp_ticks - CYC_PER_TICK + 1)) &&
 				     (ticks <= (exp_ticks + GRTC_SLEW_TICKS)),