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 --- Changes with regard to rev1:
* use TIMER_FREQ directly instead of recalculating it with rounding errors
cpu/arm920t/ep93xx/timer.c | 70 ++++++++++++++++--------------------------- 1 files changed, 26 insertions(+), 44 deletions(-)
diff --git a/cpu/arm920t/ep93xx/timer.c b/cpu/arm920t/ep93xx/timer.c index 98c759c..b1a01a0 100644 --- a/cpu/arm920t/ep93xx/timer.c +++ b/cpu/arm920t/ep93xx/timer.c @@ -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); - - 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(); + const unsigned long target = get_ticks() + usecs_to_ticks(usec);
- 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();