From 5acf3fb770d7ea3c01d7532fa1d185729a5b2551 Mon Sep 17 00:00:00 2001
From: Atis Elsts <atis.elsts@gmail.com>
Date: Thu, 21 Aug 2014 18:09:54 +0200
Subject: [PATCH 1/2] Fix time accounting on msp430 Series 5 MCU based
 platforms (wismote)

See https://github.com/contiki-os/contiki/pull/727 for explanation
---
 cpu/msp430/f5xxx/clock.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/cpu/msp430/f5xxx/clock.c b/cpu/msp430/f5xxx/clock.c
index 3cda89232..b0047a9e6 100644
--- a/cpu/msp430/f5xxx/clock.c
+++ b/cpu/msp430/f5xxx/clock.c
@@ -41,12 +41,26 @@
 
 #define MAX_TICKS (~((clock_time_t)0) / 2)
 
+#define CLOCK_LT(a, b) ((int16_t)((a)-(b)) < 0)
+
 static volatile unsigned long seconds;
 
 static volatile clock_time_t count = 0;
 /* last_tar is used for calculating clock_fine, last_ccr might be better? */
 static volatile uint16_t last_tar = 0;
 /*---------------------------------------------------------------------------*/
+static inline uint16_t
+read_tar(void)
+{
+  /* Same as clock_counter(), but can be inlined */
+  uint16_t t1, t2;
+  do {
+    t1 = TA1R;
+    t2 = TA1R;
+  } while(t1 != t2);
+  return t1;
+}
+/*---------------------------------------------------------------------------*/
 ISR(TIMER1_A1, timera1)
 {
   ENERGEST_ON(ENERGEST_TYPE_IRQ);
@@ -59,8 +73,9 @@ ISR(TIMER1_A1, timera1)
      * Occurs when timer state is toggled between STOP and CONT. */
     while(TA1CTL & MC1 && TA1CCR1 - TA1R == 1);
 
+    last_tar = read_tar();
     /* Make sure interrupt time is future */
-    do {
+    while(!CLOCK_LT(last_tar, TA1CCR1)) {
       TA1CCR1 += INTERVAL;
       ++count;
 
@@ -76,9 +91,8 @@ ISR(TIMER1_A1, timera1)
         ++seconds;
         energest_flush();
       }
-    } while((TA1CCR1 - TA1R) > INTERVAL);
-
-    last_tar = TA1R;
+      last_tar = read_tar();
+    }
 
     if(etimer_pending() &&
        (etimer_next_expiration_time() - count - 1) > MAX_TICKS) {

From 0e9c0514851d800f7b91f15484d39571280bb334 Mon Sep 17 00:00:00 2001
From: Atis Elsts <atis.elsts@gmail.com>
Date: Thu, 21 Aug 2014 18:10:53 +0200
Subject: [PATCH 2/2] Fix time accounting on TI EXP5438 MSP430x5438a
 experimenters board

---
 platform/exp5438/clock.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/platform/exp5438/clock.c b/platform/exp5438/clock.c
index 7a0dcaf72..be8fcca47 100644
--- a/platform/exp5438/clock.c
+++ b/platform/exp5438/clock.c
@@ -43,12 +43,26 @@
 
 #define MAX_TICKS (~((clock_time_t)0) / 2)
 
+#define CLOCK_LT(a, b) ((int16_t)((a)-(b)) < 0)
+
 static volatile unsigned long seconds;
 
 static volatile clock_time_t count = 0;
 /* last_tar is used for calculating clock_fine, last_ccr might be better? */
 static unsigned short last_tar = 0;
 /*---------------------------------------------------------------------------*/
+static inline uint16_t
+read_tar(void)
+{
+  /* Same as clock_counter(), but can be inlined */
+  uint16_t t1, t2;
+  do {
+    t1 = TA1R;
+    t2 = TA1R;
+  } while(t1 != t2);
+  return t1;
+}
+/*---------------------------------------------------------------------------*/
 ISR(TIMER1_A1, timera1)
 {
   ENERGEST_ON(ENERGEST_TYPE_IRQ);
@@ -59,8 +73,9 @@ ISR(TIMER1_A1, timera1)
      * Occurrs when timer state is toggled between STOP and CONT. */
     while(TA1CTL & MC1 && TA1CCR1 - TA1R == 1);
 
+    last_tar = read_tar();
     /* Make sure interrupt time is future */
-    do {
+    while(!CLOCK_LT(last_tar, TA1CCR1)) {
       /*      TACTL &= ~MC1;*/
       TA1CCR1 += INTERVAL;
       /*      TACTL |= MC1;*/
@@ -78,9 +93,8 @@ ISR(TIMER1_A1, timera1)
         ++seconds;
         energest_flush();
       }
-    } while((TA1CCR1 - TA1R) > INTERVAL);
-
-    last_tar = TA1R;
+      last_tar = read_tar();
+    }
 
     if(etimer_pending() &&
        (etimer_next_expiration_time() - count - 1) > MAX_TICKS) {