Fixes in Sys Timer test

Do not call sleep from the test thread, but let scheduler do it.
And also include the deep sleep latency in the computation of the allowed
delta for deep sleep test case.

Author: LMESTM

TESTS/mbedmicro-rtos-mbed/systimer/main.cpp

@@ -31,6 +31,14 @@ extern "C" {
 #define TEST_TICKS 42UL
 #define DELAY_DELTA_US 2500ULL
 
+/*  Use a specific delta value for deep sleep, as entry/exit adds up extra latency.
+ *  Use deep sleep latency if defined and add 1ms extra delta */
+#if defined MBED_CONF_TARGET_DEEP_SLEEP_LATENCY
+#define DEEP_SLEEP_DELAY_DELTA_US ((MBED_CONF_TARGET_DEEP_SLEEP_LATENCY * 1000ULL) + 1000ULL)
+#else
+#define DEEP_SLEEP_DELAY_DELTA_US 2500ULL
+#endif
+
 using namespace utest::v1;
 
 const us_timestamp_t DELAY_US = 1000000ULL * TEST_TICKS / OS_TICK_FREQ;
@@ -66,6 +74,11 @@ class SysTimerTest: public rtos::internal::SysTimer {
     {
         return _sem.try_acquire_for(millisec);
     }
+
+    void sem_acquire()
+    {
+        _sem.acquire();
+    }
 };
 
 timestamp_t mock_ticker_timestamp;
@@ -275,9 +288,8 @@ void test_sleep(void)
     st.schedule_tick(TEST_TICKS);
 
     TEST_ASSERT_FALSE_MESSAGE(sleep_manager_can_deep_sleep(), "Deep sleep should be disallowed");
-    while (!st.sem_try_acquire(0)) {
-        sleep();
-    }
+    st.sem_acquire();
+
     timer.stop();
     sleep_manager_unlock_deep_sleep();
 
@@ -305,20 +317,17 @@ void test_deepsleep(void)
      * so we'll use the wait_ms() function for now.
      */
     wait_ms(10);
-
     // Regular Timer might be disabled during deepsleep.
     LowPowerTimer lptimer;
     SysTimerTest st;
 
     lptimer.start();
     st.schedule_tick(TEST_TICKS);
     TEST_ASSERT_TRUE_MESSAGE(sleep_manager_can_deep_sleep_test_check(), "Deep sleep should be allowed");
-    while (!st.sem_try_acquire(0)) {
-        sleep();
-    }
+    st.sem_acquire();
     lptimer.stop();
 
-    TEST_ASSERT_UINT64_WITHIN(DELAY_DELTA_US, DELAY_US, lptimer.read_high_resolution_us());
+    TEST_ASSERT_UINT64_WITHIN(DEEP_SLEEP_DELAY_DELTA_US, DELAY_US, lptimer.read_high_resolution_us());
 }
 #endif
 #endif