Fix lp code

Author: linlingao

targets/TARGET_TI/TARGET_CC32XX/TARGET_CC3220SF/lp_ticker.c

@@ -31,9 +31,6 @@
 
 #define RTC_BITS 48u
 #define RTC_FREQ 32768u
-#define RTC_COUNTER_MSK  0xFFFFFFFFFFFFULL
-/**< Macro for wrapping values to RTC capacity. */
-#define RTC_WRAP(val) (val & RTC_COUNTER_MSK)
 
 static bool         rtc_inited  = false;
 
@@ -46,11 +43,6 @@ const ticker_info_t* lp_ticker_get_info()
     return &info;
 }
 
-void PRCM_IRQHandler(void)
-{
-    lp_ticker_irq_handler();
-}
-
 void lp_ticker_init()
 {
     if (PRCMRTCInUseGet() == true)
@@ -59,7 +51,7 @@ void lp_ticker_init()
         return;
     }
     if (!rtc_inited) {
-        NVIC_SetVector(INT_PRCM_IRQn, (uint32_t)PRCM_IRQHandler);
+        NVIC_SetVector(INT_PRCM_IRQn, (uint32_t)lp_ticker_irq_handler);
         // Set priority to highest 0
         NVIC_SetPriority(INT_PRCM_IRQn, 0);
         NVIC_ClearPendingIRQ(INT_PRCM_IRQn);
@@ -83,24 +75,10 @@ void lp_ticker_free()
 void lp_ticker_set_interrupt(timestamp_t timestamp)
 {
     // timestamp is defined as 32b.
-    unsigned long long slowctr_now; // 64b counter
-
-    // The 32KHz clock is always running. Say, to generate interrupt after 1ms or 33 ticks, if the counter is N, we need to write
-    // N + 33 to the match register.
     core_util_critical_section_enter();
-    slowctr_now = PRCMSlowClkCtrFastGet();
-
-    /* COMPARE occurs when a SC register is N and the COUNTER value transitions from N-1 to N.
-     * If the COUNTER is N, writing N+2 to a CC register is guaranteed to trigger a
-     * COMPARE event at N+2.
-     */
-    if (slowctr_now == timestamp || (slowctr_now + 1) == timestamp)
-    {
-        timestamp += 2;
-    }
     // Clear pending interrupt
     PRCMIntStatus();
-    PRCMSlowClkCtrMatchSet(RTC_WRAP((slowctr_now + timestamp)));
+    PRCMSlowClkCtrMatchSet(timestamp);
     PRCMIntEnable(PRCM_INT_SLOW_CLK_CTR);
     core_util_critical_section_exit();
 }
@@ -124,8 +102,15 @@ void lp_ticker_clear_interrupt()
 
 timestamp_t lp_ticker_read()
 {
-    // Truncate to 32b. Is it okay?
-    return (timestamp_t)PRCMSlowClkCtrFastGet();
+    // Read forever until reaching two of the same
+    volatile unsigned long long read_previous, read_current;
+    do
+    {
+        read_previous = PRCMSlowClkCtrFastGet();
+        read_current = PRCMSlowClkCtrFastGet();
+    } while (read_previous != read_current);
+
+    return read_current;
 }
 
 #endif /* DEVICE_LPTICKER */