imx-common: timer: fix 32-bit overflow

The i.MX6 common timer uses the 32-bit variable tbl (time base lower)
to record the overflow of the 32-bit counter. I.e. if the counter
overflows, the variable tbl does overflow, too.

To capture this overflow, use the variable tbu (time base upper), too.
Return the combined value of tbl and tbu.

lastinc is unused then, remove it.

Signed-off-by: Knut Wohlrab <knut.wohlrab@de.bosch.com>
Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Acked-by: Stefano Babic <sbabic@denx.de>

arch/arm/imx-common/timer.c

@@ -48,9 +48,6 @@ static struct mxc_gpt *cur_gpt = (struct mxc_gpt *)GPT1_BASE_ADDR;
 
 DECLARE_GLOBAL_DATA_PTR;
 
-#define timestamp (gd->arch.tbl)
-#define lastinc (gd->arch.lastinc)
-
 static inline unsigned long long tick_to_time(unsigned long long tick)
 {
 	tick *= CONFIG_SYS_HZ;
@@ -70,7 +67,6 @@ static inline unsigned long long us_to_tick(unsigned long long usec)
 int timer_init(void)
 {
 	int i;
-	ulong val;
 
 	/* setup GP Timer 1 */
 	__raw_writel(GPTCR_SWR, &cur_gpt->control);
@@ -85,9 +81,8 @@ int timer_init(void)
 	i = __raw_readl(&cur_gpt->control);
 	__raw_writel(i | GPTCR_CLKSOURCE_32 | GPTCR_TEN, &cur_gpt->control);
 
-	val = __raw_readl(&cur_gpt->counter);
-	lastinc = val / (MXC_CLK32 / CONFIG_SYS_HZ);
-	timestamp = 0;
+	gd->arch.tbl = __raw_readl(&cur_gpt->counter);
+	gd->arch.tbu = 0;
 
 	return 0;
 }
@@ -96,18 +91,11 @@ unsigned long long get_ticks(void)
 {
 	ulong now = __raw_readl(&cur_gpt->counter); /* current tick value */
 
-	if (now >= lastinc) {
-		/*
-		 * normal mode (non roll)
-		 * move stamp forward with absolut diff ticks
-		 */
-		timestamp += (now - lastinc);
-	} else {
-		/* we have rollover of incrementer */
-		timestamp += (0xFFFFFFFF - lastinc) + now;
-	}
-	lastinc = now;
-	return timestamp;
+	/* increment tbu if tbl has rolled over */
+	if (now < gd->arch.tbl)
+		gd->arch.tbu++;
+	gd->arch.tbl = now;
+	return (((unsigned long long)gd->arch.tbu) << 32) | gd->arch.tbl;
 }
 
 ulong get_timer_masked(void)