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ep93xx: Refactoring of timer code

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ep93xx: Refactoring of the timer code, including the following changes

 * use a free running timer instead of a periodical one
 * use unsigned long long for total number of ticks
 * hold the timer state in a structure instead of separate variables
 * increment the timer counter instead of decrementing it
 * remove unused function udelay_masked()
 * remove unused function set_timer()

Signed-off-by: Matthias Kaehlcke <matthias@kaehlcke.net>
This commit is contained in:
Matthias Kaehlcke 2010-02-24 00:22:09 +01:00 committed by Tom Rix
parent d9f505e3cd
commit c7ad13a242
1 changed files with 26 additions and 44 deletions
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70
cpu/arm920t/ep93xx/timer.c
View file

@ -34,16 +34,18 @@
#include <div64.h>
#define TIMER_CLKSEL (1 << 3)
#define TIMER_MODE (1 << 6)
#define TIMER_ENABLE (1 << 7)
#define TIMER_FREQ 508469
#define TIMER_LOAD_VAL (TIMER_FREQ / CONFIG_SYS_HZ)
#define TIMER_FREQ 508469
#define TIMER_MAX_VAL 0xFFFFFFFF
static ulong timestamp;
static ulong lastdec;
static struct ep93xx_timer
{
unsigned long long ticks;
unsigned long last_update;
} timer;
static inline unsigned long clk_to_systicks(unsigned long clk_ticks)
static inline unsigned long clk_to_systicks(unsigned long long clk_ticks)
{
unsigned long long sys_ticks = (clk_ticks * CONFIG_SYS_HZ);
do_div(sys_ticks, TIMER_FREQ);
@ -57,10 +59,10 @@ static inline unsigned long usecs_to_ticks(unsigned long usecs)
if (usecs >= 1000) {
ticks = usecs / 1000;
ticks *= (TIMER_LOAD_VAL * CONFIG_SYS_HZ);
ticks *= TIMER_FREQ;
ticks /= 1000;
} else {
ticks = usecs * TIMER_LOAD_VAL * CONFIG_SYS_HZ;
ticks = usecs * TIMER_FREQ;
ticks /= (1000 * 1000);
}
@ -71,7 +73,7 @@ static inline unsigned long read_timer(void)
{
struct timer_regs *timer = (struct timer_regs *)TIMER_BASE;
return readl(&timer->timer3.value);
return TIMER_MAX_VAL - readl(&timer->timer3.value);
}
/*
@ -81,17 +83,15 @@ unsigned long long get_ticks(void)
{
const unsigned long now = read_timer();
if (lastdec >= now) {
/* normal mode */
timestamp += lastdec - now;
} else {
/* we have an overflow ... */
timestamp += lastdec + TIMER_LOAD_VAL - now;
}
if (now >= timer.last_update)
timer.ticks += now - timer.last_update;
else
/* an overflow occurred */
timer.ticks += TIMER_MAX_VAL - timer.last_update + now;
lastdec = now;
timer.last_update = now;
return timestamp;
return timer.ticks;
}
unsigned long get_timer_masked(void)
@ -106,8 +106,8 @@ unsigned long get_timer(unsigned long base)
void reset_timer_masked(void)
{
lastdec = read_timer();
timestamp = 0;
timer.last_update = read_timer();
timer.ticks = 0;
}
void reset_timer(void)
@ -115,28 +115,11 @@ void reset_timer(void)
reset_timer_masked();
}
void set_timer(unsigned long t)
{
timestamp = t;
}
void __udelay(unsigned long usec)
{
const unsigned long ticks = usecs_to_ticks(usec);
const unsigned long target = clk_to_systicks(ticks) + get_timer(0);
const unsigned long target = get_ticks() + usecs_to_ticks(usec);
while (get_timer_masked() < target)
/* noop */;
}
void udelay_masked(unsigned long usec)
{
const unsigned long ticks = usecs_to_ticks(usec);
const unsigned long target = clk_to_systicks(ticks) + get_timer(0);
reset_timer_masked();
while (get_timer_masked() < target)
while (get_ticks() < target)
/* noop */;
}
@ -147,12 +130,11 @@ int timer_init(void)
/* use timer 3 with 508KHz and free running */
writel(TIMER_CLKSEL, &timer->timer3.control);
/* auto load, manual update of Timer 3 */
lastdec = TIMER_LOAD_VAL;
writel(TIMER_LOAD_VAL, &timer->timer3.load);
/* set initial timer value 3 */
writel(TIMER_MAX_VAL, &timer->timer3.load);
/* Enable the timer and periodic mode */
writel(TIMER_ENABLE | TIMER_MODE | TIMER_CLKSEL,
/* Enable the timer */
writel(TIMER_ENABLE | TIMER_CLKSEL,
&timer->timer3.control);
reset_timer_masked();