Introduce common timer functions

Many platforms duplicate pretty much the same timer code yet they all have
a 32-bit freerunning counter register. Create a common implementation that
minimally requires 2 or 3 defines to add timer support:

CONFIG_SYS_TIMER_RATE - Clock rate of the timer counter
CONFIG_SYS_TIMER_COUNTER - Address of 32-bit counter
CONFIG_SYS_TIMER_COUNTS_DOWN - Define if counter counts down

All functions are weak or ifdef'ed so they can still be overriden by any
platform.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>

include/asm-generic/global_data.h

@@ -72,6 +72,8 @@ typedef struct global_data {
 #if defined(CONFIG_SYS_I2C)
 	int		cur_i2c_bus;	/* current used i2c bus */
 #endif
+	unsigned long timebase_h;
+	unsigned long timebase_l;
 	struct arch_global_data arch;	/* architecture-specific data */
 } gd_t;
 #endif

lib/time.c

@@ -7,6 +7,8 @@
 
 #include <common.h>
 #include <watchdog.h>
+#include <div64.h>
+#include <asm/io.h>
 
 #if CONFIG_SYS_HZ != 1000
 #warning "CONFIG_SYS_HZ must be 1000 and should not be defined by platforms"
@@ -16,6 +18,77 @@
 # define CONFIG_WD_PERIOD	(10 * 1000 * 1000)	/* 10 seconds default*/
 #endif
 
+DECLARE_GLOBAL_DATA_PTR;
+
+#ifdef CONFIG_SYS_TIMER_RATE
+ulong notrace get_tbclk(void)
+{
+	return CONFIG_SYS_TIMER_RATE;
+}
+#endif
+
+#ifdef CONFIG_SYS_TIMER_COUNTER
+unsigned long notrace timer_read_counter(void)
+{
+#ifdef CONFIG_SYS_TIMER_COUNTS_DOWN
+	return ~readl(CONFIG_SYS_TIMER_COUNTER);
+#else
+	return readl(CONFIG_SYS_TIMER_COUNTER);
+#endif
+}
+#else
+extern unsigned long timer_read_counter(void);
+#endif
+
+unsigned long long __weak notrace get_ticks(void)
+{
+	unsigned long now = timer_read_counter();
+
+	/* increment tbu if tbl has rolled over */
+	if (now < gd->timebase_l)
+		gd->timebase_h++;
+	gd->timebase_l = now;
+	return ((unsigned long long)gd->timebase_h << 32) | gd->timebase_l;
+}
+
+static unsigned long long notrace tick_to_time(unsigned long long tick)
+{
+	unsigned int div = get_tbclk();
+
+	tick *= CONFIG_SYS_HZ;
+	do_div(tick, div);
+	return tick;
+}
+
+ulong __weak get_timer(ulong base)
+{
+	return tick_to_time(get_ticks()) - base;
+}
+
+unsigned long __weak notrace timer_get_us(void)
+{
+	return tick_to_time(get_ticks() * 1000);
+}
+static unsigned long long usec_to_tick(unsigned long usec)
+{
+	unsigned long long tick = usec * get_tbclk();
+	usec *= get_tbclk();
+	do_div(tick, 1000000);
+	return tick;
+}
+
+void __weak __udelay(unsigned long usec)
+{
+	unsigned long long tmp;
+	ulong tmo;
+
+	tmo = usec_to_tick(usec);
+	tmp = get_ticks() + tmo;	/* get current timestamp */
+
+	while (get_ticks() < tmp)	/* loop till event */
+		 /*NOP*/;
+}
+
 /* ------------------------------------------------------------------------- */
 
 void udelay(unsigned long usec)