Tegra2: Add microsecond timer function

These functions provide access to the high resolution microsecond timer
and tidy up a global variable in the code.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/cpu/armv7/tegra2/timer.c b/arch/arm/cpu/armv7/tegra2/timer.c
index 0b9fa64..b12b12c 100644
--- a/arch/arm/cpu/armv7/tegra2/timer.c
+++ b/arch/arm/cpu/armv7/tegra2/timer.c
@@ -38,13 +38,12 @@
 #include <common.h>
 #include <asm/io.h>
 #include <asm/arch/tegra2.h>
+#include <asm/arch/timer.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
-struct timerus *timer_base = (struct timerus *)NV_PA_TMRUS_BASE;
-
 /* counter runs at 1MHz */
-#define TIMER_CLK	(1000000)
+#define TIMER_CLK	1000000
 #define TIMER_LOAD_VAL	0xffffffff
 
 /* timer without interrupts */
@@ -57,10 +56,10 @@
 void __udelay(unsigned long usec)
 {
 	long tmo = usec * (TIMER_CLK / 1000) / 1000;
-	unsigned long now, last = readl(&timer_base->cntr_1us);
+	unsigned long now, last = timer_get_us();
 
 	while (tmo > 0) {
-		now = readl(&timer_base->cntr_1us);
+		now = timer_get_us();
 		if (last > now) /* count up timer overflow */
 			tmo -= TIMER_LOAD_VAL - last + now;
 		else
@@ -74,7 +73,7 @@
 	ulong now;
 
 	/* current tick value */
-	now = readl(&timer_base->cntr_1us) / (TIMER_CLK / CONFIG_SYS_HZ);
+	now = timer_get_us() / (TIMER_CLK / CONFIG_SYS_HZ);
 
 	if (now >= gd->lastinc)	/* normal mode (non roll) */
 		/* move stamp forward with absolute diff ticks */
@@ -103,3 +102,10 @@
 {
 	return CONFIG_SYS_HZ;
 }
+
+unsigned long timer_get_us(void)
+{
+	struct timerus *timer_base = (struct timerus *)NV_PA_TMRUS_BASE;
+
+	return readl(&timer_base->cntr_1us);
+}