diff options
Diffstat (limited to 'arch/arm/mach-at91/at91rm9200_time.c')
| -rw-r--r-- | arch/arm/mach-at91/at91rm9200_time.c | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/arch/arm/mach-at91/at91rm9200_time.c b/arch/arm/mach-at91/at91rm9200_time.c new file mode 100644 index 00000000000..949199a244c --- /dev/null +++ b/arch/arm/mach-at91/at91rm9200_time.c @@ -0,0 +1,146 @@ +/* + * linux/arch/arm/mach-at91/at91rm9200_time.c + * + * Copyright (C) 2003 SAN People + * Copyright (C) 2003 ATMEL + * + * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#include <linux/init.h> +#include <linux/interrupt.h> +#include <linux/irq.h> +#include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/time.h> + +#include <asm/hardware.h> +#include <asm/io.h> +#include <asm/mach/time.h> + +#include <asm/arch/at91_st.h> + +static unsigned long last_crtr; + +/* + * The ST_CRTR is updated asynchronously to the master clock. It is therefore + * necessary to read it twice (with the same value) to ensure accuracy. + */ +static inline unsigned long read_CRTR(void) { + unsigned long x1, x2; + + do { + x1 = at91_sys_read(AT91_ST_CRTR); + x2 = at91_sys_read(AT91_ST_CRTR); + } while (x1 != x2); + + return x1; +} + +/* + * Returns number of microseconds since last timer interrupt. Note that interrupts + * will have been disabled by do_gettimeofday() + * 'LATCH' is hwclock ticks (see CLOCK_TICK_RATE in timex.h) per jiffy. + * 'tick' is usecs per jiffy (linux/timex.h). + */ +static unsigned long at91rm9200_gettimeoffset(void) +{ + unsigned long elapsed; + + elapsed = (read_CRTR() - last_crtr) & AT91_ST_ALMV; + + return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH; +} + +/* + * IRQ handler for the timer. + */ +static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id) +{ + if (at91_sys_read(AT91_ST_SR) & AT91_ST_PITS) { /* This is a shared interrupt */ + write_seqlock(&xtime_lock); + + while (((read_CRTR() - last_crtr) & AT91_ST_ALMV) >= LATCH) { + timer_tick(); + last_crtr = (last_crtr + LATCH) & AT91_ST_ALMV; + } + + write_sequnlock(&xtime_lock); + + return IRQ_HANDLED; + } + else + return IRQ_NONE; /* not handled */ +} + +static struct irqaction at91rm9200_timer_irq = { + .name = "at91_tick", + .flags = IRQF_SHARED | IRQF_DISABLED | IRQF_TIMER, + .handler = at91rm9200_timer_interrupt +}; + +void at91rm9200_timer_reset(void) +{ + last_crtr = 0; + + /* Real time counter incremented every 30.51758 microseconds */ + at91_sys_write(AT91_ST_RTMR, 1); + + /* Set Period Interval timer */ + at91_sys_write(AT91_ST_PIMR, LATCH); + + /* Clear any pending interrupts */ + (void) at91_sys_read(AT91_ST_SR); + + /* Enable Period Interval Timer interrupt */ + at91_sys_write(AT91_ST_IER, AT91_ST_PITS); +} + +/* + * Set up timer interrupt. + */ +void __init at91rm9200_timer_init(void) +{ + /* Disable all timer interrupts */ + at91_sys_write(AT91_ST_IDR, AT91_ST_PITS | AT91_ST_WDOVF | AT91_ST_RTTINC | AT91_ST_ALMS); + (void) at91_sys_read(AT91_ST_SR); /* Clear any pending interrupts */ + + /* Make IRQs happen for the system timer */ + setup_irq(AT91_ID_SYS, &at91rm9200_timer_irq); + + /* Change the kernel's 'tick' value to 10009 usec. (the default is 10000) */ + tick_usec = (LATCH * 1000000) / CLOCK_TICK_RATE; + + /* Initialize and enable the timer interrupt */ + at91rm9200_timer_reset(); +} + +#ifdef CONFIG_PM +static void at91rm9200_timer_suspend(void) +{ + /* disable Period Interval Timer interrupt */ + at91_sys_write(AT91_ST_IDR, AT91_ST_PITS); +} +#else +#define at91rm9200_timer_suspend NULL +#endif + +struct sys_timer at91rm9200_timer = { + .init = at91rm9200_timer_init, + .offset = at91rm9200_gettimeoffset, + .suspend = at91rm9200_timer_suspend, + .resume = at91rm9200_timer_reset, +}; + |