[U-Boot] [PATCH] ep93xx timer: Fix get_ticks() and usecs_to_ticks()

[Matthias Kaehlcke]

ep93xx timer: Make get_ticks() consistent with get_tbclk(), returning
a value with CONFIG_SYS_HZ resolution. This fix obsoletes the function
clk_to_systicks(), leading to a simplification of the timer code. Further
a variable in usecs_to_ticks() is promoted to a 64-bit value, to avoid
overflows of intermediate values.

Signed-off-by: Matthias Kaehlcke <matthias at kaehlcke.net>
Tested-by: Alessandro Rubini <rubini-list at gnudd.com>

---
 cpu/arm920t/ep93xx/timer.c |   83 +++++++++++++++++++------------------------
 1 files changed, 37 insertions(+), 46 deletions(-)

diff --git a/cpu/arm920t/ep93xx/timer.c b/cpu/arm920t/ep93xx/timer.c
index b1a01a0..c4c1fb0 100644
--- a/cpu/arm920t/ep93xx/timer.c
+++ b/cpu/arm920t/ep93xx/timer.c
@@ -1,8 +1,7 @@
 /*
  * Cirrus Logic EP93xx timer support.
  *
- * Copyright (C) 2009, 2010
- * Matthias Kaehlcke <matthias at kaehlcke.net>
+ * Copyright (C) 2009, 2010 Matthias Kaehlcke <matthias at kaehlcke.net>
  *
  * Copyright (C) 2004, 2005
  * Cory T. Tusar, Videon Central, Inc., <ctusar at videon-central.com>
@@ -36,67 +35,55 @@
 #define TIMER_CLKSEL	(1 << 3)
 #define TIMER_ENABLE	(1 << 7)
 
-#define TIMER_FREQ			508469
+#define TIMER_FREQ			508469		/* ticks / second */
 #define TIMER_MAX_VAL			0xFFFFFFFF
 
 static struct ep93xx_timer
 {
 	unsigned long long ticks;
-	unsigned long last_update;
+	unsigned long last_read;
 } timer;
 
-static inline unsigned long clk_to_systicks(unsigned long long clk_ticks)
+static inline unsigned long long usecs_to_ticks(unsigned long usecs)
 {
-	unsigned long long sys_ticks = (clk_ticks * CONFIG_SYS_HZ);
-	do_div(sys_ticks, TIMER_FREQ);
-
-	return (unsigned long)sys_ticks;
-}
-
-static inline unsigned long usecs_to_ticks(unsigned long usecs)
-{
-	unsigned long ticks;
-
-	if (usecs >= 1000) {
-		ticks = usecs / 1000;
-		ticks *= TIMER_FREQ;
-		ticks /= 1000;
-	} else {
-		ticks = usecs * TIMER_FREQ;
-		ticks /= (1000 * 1000);
-	}
+	unsigned long long ticks = usecs * TIMER_FREQ;
+	do_div(ticks, 1000 * 1000);
 
 	return ticks;
 }
 
-static inline unsigned long read_timer(void)
+static inline void read_timer(void)
 {
-	struct timer_regs *timer = (struct timer_regs *)TIMER_BASE;
+	struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
+	const unsigned long now = TIMER_MAX_VAL - readl(&timer_regs->timer3.value);
+
+	if (now >= timer.last_read)
+		timer.ticks += now - timer.last_read;
+	else
+		/* an overflow occurred */
+		timer.ticks += TIMER_MAX_VAL - timer.last_read + now;
 
-	return TIMER_MAX_VAL - readl(&timer->timer3.value);
+	timer.last_read = now;
 }
 
 /*
- * timer without interrupts
+ * Get the number of ticks (in CONFIG_SYS_HZ resolution)
  */
 unsigned long long get_ticks(void)
 {
-	const unsigned long now = read_timer();
+	unsigned long long sys_ticks;
 
-	if (now >= timer.last_update)
-		timer.ticks += now - timer.last_update;
-	else
-		/* an overflow occurred */
-		timer.ticks += TIMER_MAX_VAL - timer.last_update + now;
+	read_timer();
 
-	timer.last_update = now;
+	sys_ticks = timer.ticks * CONFIG_SYS_HZ;
+	do_div(sys_ticks, TIMER_FREQ);
 
-	return timer.ticks;
+	return sys_ticks;
 }
 
 unsigned long get_timer_masked(void)
 {
-	return clk_to_systicks(get_ticks());
+	return get_ticks();
 }
 
 unsigned long get_timer(unsigned long base)
@@ -106,7 +93,7 @@ unsigned long get_timer(unsigned long base)
 
 void reset_timer_masked(void)
 {
-	timer.last_update = read_timer();
+	read_timer();
 	timer.ticks = 0;
 }
 
@@ -117,25 +104,29 @@ void reset_timer(void)
 
 void __udelay(unsigned long usec)
 {
-	const unsigned long target = get_ticks() + usecs_to_ticks(usec);
+	unsigned long long target;
+
+	read_timer();
+
+	target = timer.ticks + usecs_to_ticks(usec);
 
-	while (get_ticks() < target)
-		/* noop */;
+	while (timer.ticks < target)
+		read_timer();
 }
 
 int timer_init(void)
 {
-	struct timer_regs *timer = (struct timer_regs *)TIMER_BASE;
+	struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
 
-	/* use timer 3 with 508KHz and free running */
-	writel(TIMER_CLKSEL, &timer->timer3.control);
+	/* use timer 3 with 508KHz and free running, not enabled now */
+	writel(TIMER_CLKSEL, &timer_regs->timer3.control);
 
-	/* set initial timer value 3 */
-	writel(TIMER_MAX_VAL, &timer->timer3.load);
+	/* set initial timer value */
+	writel(TIMER_MAX_VAL, &timer_regs->timer3.load);
 
 	/* Enable the timer */
 	writel(TIMER_ENABLE | TIMER_CLKSEL,
-		&timer->timer3.control);
+		&timer_regs->timer3.control);
 
 	reset_timer_masked();
 
-- 
1.6.5