tests-mbed_hal-sleep: add exception for STM LPTIM targets.

On some targets like STM family boards with LPTIM enabled an interrupt is triggered on counter rollover.
We need special handling for cases when next_match_timestamp < start_timestamp (interrupt is to be fired after rollover).
In such case after first wake-up we need to reset interrupt and go back to sleep waiting for the valid one.

Background:
There is an errata in LPTIM specification that explains that CMP Flag
condition is not an exact match (COUNTER = MATCH) but rather a
comparison (COUNTER >= MATCH).

As a consequence the interrupt is firing early than expected when
programing a timestamp after the 0xFFFF wrap-around.

In order to
work-around this issue, we implement the below work-around.
In case timestamp is after the work-around, let's decide to program the
CMP value to 0xFFFF, which is the wrap-around value. There would anyway be
a wake-up at the time of wrap-around to let the OS update the system time.
When the wrap-around interrupt happen, OS will check the current time and
program again the timestamp to the proper value.

Author: mprse

TESTS/mbed_hal/sleep/main.cpp

@@ -124,6 +124,16 @@ void deepsleep_lpticker_test()
 
         sleep();
 
+        /* On some targets like STM family boards with LPTIM enabled an interrupt is triggered on counter rollover.
+           We need special handling for cases when next_match_timestamp < start_timestamp (interrupt is to be fired after rollover).
+           In such case after first wake-up we need to reset interrupt and go back to sleep waiting for the valid one. */
+#if MBED_CONF_TARGET_LPTICKER_LPTIM
+        if ((next_match_timestamp < start_timestamp) && lp_ticker_read() < next_match_timestamp) {
+            lp_ticker_set_interrupt(next_match_timestamp);
+            sleep();
+        }
+#endif
+
         const timestamp_t wakeup_timestamp = lp_ticker_read();
 
         sprintf(info, "Delta ticks: %u, Ticker width: %u, Expected wake up tick: %d, Actual wake up tick: %d, delay ticks: %d, wake up after ticks: %d",