diff options
Diffstat (limited to 'arch/arm/cpu/arm920t/ep93xx/timer.c')
-rw-r--r-- | arch/arm/cpu/arm920t/ep93xx/timer.c | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/arch/arm/cpu/arm920t/ep93xx/timer.c b/arch/arm/cpu/arm920t/ep93xx/timer.c new file mode 100644 index 0000000000..4a0ce4da64 --- /dev/null +++ b/arch/arm/cpu/arm920t/ep93xx/timer.c @@ -0,0 +1,143 @@ +/* + * Cirrus Logic EP93xx timer support. + * + * Copyright (C) 2009, 2010 Matthias Kaehlcke <matthias@kaehlcke.net> + * + * Copyright (C) 2004, 2005 + * Cory T. Tusar, Videon Central, Inc., <ctusar@videon-central.com> + * + * Based on the original intr.c Cirrus Logic EP93xx Rev D. interrupt support, + * author unknown. + * + * See file CREDITS for list of people who contributed to this project. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY + * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +#include <common.h> +#include <linux/types.h> +#include <asm/arch/ep93xx.h> +#include <asm/io.h> +#include <div64.h> + +#define TIMER_CLKSEL (1 << 3) +#define TIMER_ENABLE (1 << 7) + +#define TIMER_FREQ 508469 /* ticks / second */ +#define TIMER_MAX_VAL 0xFFFFFFFF + +static struct ep93xx_timer +{ + unsigned long long ticks; + unsigned long last_read; +} timer; + +static inline unsigned long long usecs_to_ticks(unsigned long usecs) +{ + unsigned long long ticks = (unsigned long long)usecs * TIMER_FREQ; + do_div(ticks, 1000 * 1000); + + return ticks; +} + +static inline void read_timer(void) +{ + 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; + + timer.last_read = now; +} + +/* + * Get the number of ticks (in CONFIG_SYS_HZ resolution) + */ +unsigned long long get_ticks(void) +{ + unsigned long long sys_ticks; + + read_timer(); + + sys_ticks = timer.ticks * CONFIG_SYS_HZ; + do_div(sys_ticks, TIMER_FREQ); + + return sys_ticks; +} + +unsigned long get_timer_masked(void) +{ + return get_ticks(); +} + +unsigned long get_timer(unsigned long base) +{ + return get_timer_masked() - base; +} + +void reset_timer_masked(void) +{ + read_timer(); + timer.ticks = 0; +} + +void reset_timer(void) +{ + reset_timer_masked(); +} + +void __udelay(unsigned long usec) +{ + unsigned long long target; + + read_timer(); + + target = timer.ticks + usecs_to_ticks(usec); + + while (timer.ticks < target) + read_timer(); +} + +int timer_init(void) +{ + struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE; + + /* use timer 3 with 508KHz and free running, not enabled now */ + writel(TIMER_CLKSEL, &timer_regs->timer3.control); + + /* set initial timer value */ + writel(TIMER_MAX_VAL, &timer_regs->timer3.load); + + /* Enable the timer */ + writel(TIMER_ENABLE | TIMER_CLKSEL, + &timer_regs->timer3.control); + + reset_timer_masked(); + + return 0; +} + +/* + * This function is derived from PowerPC code (timebase clock frequency). + * On ARM it returns the number of timer ticks per second. + */ +unsigned long get_tbclk(void) +{ + return CONFIG_SYS_HZ; +} |