[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 <matth...@kaehlcke.net>
Tested-by: Alessandro Rubini <rubini-l...@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 <matth...@kaehlcke.net>
+ * Copyright (C) 2009, 2010 Matthias Kaehlcke <matth...@kaehlcke.net>
  *
  * Copyright (C) 2004, 2005
  * Cory T. Tusar, Videon Central, Inc., <ctu...@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

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