| /* |
| * linux/arch/arm/mach-at91rm9200/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> |
| |
| 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, struct pt_regs *regs) |
| { |
| 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(regs); |
| 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 = SA_SHIRQ | SA_INTERRUPT | SA_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); |
| |
| /* 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, |
| }; |
| |