[BEETLE] Fix Lp_Ticker read

MBED OS requires an lp_ticker_read function that returns a 32bit
value in microseconds. This can not be represented directly on
the Beetle Dual Timer Load register.

max_us_on_reg = (0xFFFFFFFF ticks)/DIVIDER_US

This patch introduces an intermediate layer that counts the timer wraps
around and returns the correct value of us to the MBED library.

Signed-off-by: Vincenzo Frascino <[email protected]>

Author: fvincenzo

hal/targets/cmsis/TARGET_ARM_SSG/TARGET_BEETLE/apb_dualtimer.c

@@ -228,6 +228,7 @@ void DualTimer_SetInterrupt_1(uint32_t timer, uint32_t time_us,
             timerenable_t mode)
 {
     uint32_t dualtimerControl = 0;
+    uint32_t load_time_us = 0;
     /* Verify if the Timer is enabled */
     if (DualTimer_isEnabled(timer) == 1) {
         /* Disable Timer */
@@ -237,9 +238,15 @@ void DualTimer_SetInterrupt_1(uint32_t timer, uint32_t time_us,
         (DualTimers[timer].dualtimer1)->TimerControl =
                                 CMSDK_DUALTIMER_CTRL_INTEN_Msk
                                 | dualtimerControl;
+
+        /* Check time us condition */
+        if(time_us == DUALTIMER_DEFAULT_RELOAD)
+            load_time_us = DUALTIMER_MAX_VALUE;
+        else
+            load_time_us = time_us * DUALTIMER_TICKS_US;
+
         /* Reload Value */
-        DualTimers[timer].dualtimer1Reload = (time_us)
-                                * DUALTIMER_TICKS_US;
+        DualTimers[timer].dualtimer1Reload = load_time_us;
         (DualTimers[timer].dualtimer1)->TimerLoad =
                                 DualTimers[timer].dualtimer1Reload;
         /* Enable Counter */
@@ -260,6 +267,7 @@ void DualTimer_SetInterrupt_2(uint32_t timer, uint32_t time_us,
             timerenable_t mode)
 {
     uint32_t dualtimerControl = 0;
+    uint32_t load_time_us = 0;
     /* Verify if the Timer is enabled */
     if (DualTimer_isEnabled(timer) == 1) {
         /* Disable Timer */
@@ -269,9 +277,15 @@ void DualTimer_SetInterrupt_2(uint32_t timer, uint32_t time_us,
         (DualTimers[timer].dualtimer2)->TimerControl =
                                 CMSDK_DUALTIMER_CTRL_INTEN_Msk
                                 | dualtimerControl;
+
+        /* Check time us condition */
+        if(time_us == DUALTIMER_DEFAULT_RELOAD)
+            load_time_us = DUALTIMER_MAX_VALUE;
+        else
+            load_time_us = time_us * DUALTIMER_TICKS_US;
+
         /* Reload Value */
-        DualTimers[timer].dualtimer2Reload = (time_us)
-                                * DUALTIMER_TICKS_US;
+        DualTimers[timer].dualtimer2Reload = load_time_us;
         (DualTimers[timer].dualtimer2)->TimerLoad =
                                 DualTimers[timer].dualtimer2Reload;
         /* Enable Counter */
@@ -358,3 +372,22 @@ uint32_t DualTimer_GetTicksUS(uint32_t timer)
     }
     return 0;
 }
+
+/*
+ * DualTimer_GetReloadValue(): returns the load value of the selected
+ * singletimer.
+ * timer: timer associated with the Ticks per us
+ * singletimer: selected singletimer
+ * @return: reload value of the selected singletimer - 0 if timer is disabled
+ */
+uint32_t DualTimer_GetReloadValue(uint32_t timer, uint32_t singletimer)
+{
+    /* Verify if the Timer is enabled */
+    if (DualTimer_isEnabled(timer) == 1) {
+        if (singletimer == SINGLETIMER1)
+            return DualTimers[timer].dualtimer1Reload / DUALTIMER_TICKS_US;
+        else
+            return DualTimers[timer].dualtimer2Reload / DUALTIMER_TICKS_US;
+    }
+    return 0;
+}

hal/targets/cmsis/TARGET_ARM_SSG/TARGET_BEETLE/apb_dualtimer.h

@@ -50,6 +50,9 @@ typedef uint8_t timerenable_t;
 #define DUALTIMER_ONESHOT_MASK  (3)
 #define DUALTIMER_ONESHOT       (1 << DUALTIMER_ONESHOT_MASK)
 
+/* Default reload */
+#define DUALTIMER_DEFAULT_RELOAD    0xFFFFFFFF
+
 /*
  * DualTimer_Enable(): Enables a hardware timer
  * timer: timer to be enabled
@@ -136,6 +139,15 @@ uint32_t DualTimer_GetIRQInfo(uint32_t dualtimer);
  */
 uint32_t DualTimer_GetTicksUS(uint32_t timer);
 
+/*
+ * DualTimer_GetReloadValue(): returns the load value of the selected
+ * singletimer.
+ * timer: timer associated with the Ticks per us
+ * singletimer: selected singletimer
+ * @return: reload value of the selected singletimer
+ */
+uint32_t DualTimer_GetReloadValue(uint32_t timer, uint32_t singletimer);
+
 #ifdef __cplusplus
 }
 #endif

hal/targets/hal/TARGET_ARM_SSG/TARGET_BEETLE/lp_ticker.c

@@ -25,8 +25,10 @@
 static uint32_t lp_ticker_initialized = 0;
 /* lp_ticker reload value */
 static uint32_t lp_ticker_reload = 0x0; /* Max Value */
-/* Store Overflow Count */
-static uint32_t lp_ticker_overflows_count = 0;
+/* Store Overflow Delta */
+static uint32_t lp_ticker_overflows_delta = 0;
+/* lp_ticker Overflow limit */
+static uint32_t lp_ticker_overflow_limit = 0;
 
 #if DEVICE_LOWPOWERTIMER
 /**
@@ -36,7 +38,13 @@ void __lp_ticker_irq_handler(void)
 {
     if (DualTimer_GetIRQInfo(DUALTIMER0) == SINGLETIMER2) {
         DualTimer_ClearInterrupt(DUALTIMER0);
-        lp_ticker_overflows_count++;
+        /*
+         * For each overflow event adds the timer max represented value to
+         * the delta. This allows the lp_ticker to keep track of the elapsed
+         * time:
+         * elapsed_time = (num_overflow * overflow_limit) + current_time
+         */
+        lp_ticker_overflows_delta += lp_ticker_overflow_limit;
     } else {
         lp_ticker_irq_handler();
     }
@@ -67,6 +75,20 @@ void lp_ticker_init(void)
     NVIC_SetVector((IRQn_Type)lp_ticker_irqn,
                 (uint32_t)__lp_ticker_irq_handler);
     NVIC_EnableIRQ((IRQn_Type)lp_ticker_irqn);
+
+    /* DualTimer set interrupt on SINGLETIMER2 */
+    DualTimer_SetInterrupt_2(DUALTIMER0, DUALTIMER_DEFAULT_RELOAD,
+                DUALTIMER_COUNT_32 | DUALTIMER_PERIODIC);
+
+    /*
+     * Set lp_ticker Overflow limit. The lp_ticker overflow limit is required
+     * to calculated the return value of the lp_ticker read function in us
+     * on 32bit.
+     * A 32bit us value cannot be represented directly in the Dual Timer Load
+     * register if it is greater than (0xFFFFFFFF ticks)/DUALTIMER_DIVIDER_US.
+     */
+    lp_ticker_overflow_limit = DualTimer_GetReloadValue(DUALTIMER0,
+                SINGLETIMER2);
 }
 
 /**
@@ -82,7 +104,7 @@ uint32_t lp_ticker_read(void)
         lp_ticker_init();
 
     /* Read Timer Value */
-    microseconds = DualTimer_Read_2(DUALTIMER0);
+    microseconds = lp_ticker_overflows_delta + DualTimer_Read_2(DUALTIMER0);
 
     return microseconds;
 }