1/* 2 * linux/arch/arm/mach-at91/at91rm9200_time.c 3 * 4 * Copyright (C) 2003 SAN People 5 * Copyright (C) 2003 ATMEL 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation; either version 2 of the License, or 10 * (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program; if not, write to the Free Software 19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 20 */ 21 22#include <linux/init.h> 23#include <linux/interrupt.h> 24#include <linux/irq.h> 25#include <linux/kernel.h> 26#include <linux/sched.h> 27#include <linux/time.h> 28 29#include <asm/hardware.h> 30#include <asm/io.h> 31#include <asm/mach/time.h> 32 33#include <asm/arch/at91_st.h> 34 35static unsigned long last_crtr; 36 37/* 38 * The ST_CRTR is updated asynchronously to the master clock. It is therefore 39 * necessary to read it twice (with the same value) to ensure accuracy. 40 */ 41static inline unsigned long read_CRTR(void) { 42 unsigned long x1, x2; 43 44 do { 45 x1 = at91_sys_read(AT91_ST_CRTR); 46 x2 = at91_sys_read(AT91_ST_CRTR); 47 } while (x1 != x2); 48 49 return x1; 50} 51 52/* 53 * Returns number of microseconds since last timer interrupt. Note that interrupts 54 * will have been disabled by do_gettimeofday() 55 * 'LATCH' is hwclock ticks (see CLOCK_TICK_RATE in timex.h) per jiffy. 56 * 'tick' is usecs per jiffy (linux/timex.h). 57 */ 58static unsigned long at91rm9200_gettimeoffset(void) 59{ 60 unsigned long elapsed; 61 62 elapsed = (read_CRTR() - last_crtr) & AT91_ST_ALMV; 63 64 return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH; 65} 66 67/* 68 * IRQ handler for the timer. 69 */ 70static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id) 71{ 72 if (at91_sys_read(AT91_ST_SR) & AT91_ST_PITS) { /* This is a shared interrupt */ 73 write_seqlock(&xtime_lock); 74 75 while (((read_CRTR() - last_crtr) & AT91_ST_ALMV) >= LATCH) { 76 timer_tick(); 77 last_crtr = (last_crtr + LATCH) & AT91_ST_ALMV; 78 } 79 80 write_sequnlock(&xtime_lock); 81 82 return IRQ_HANDLED; 83 } 84 else 85 return IRQ_NONE; /* not handled */ 86} 87 88static struct irqaction at91rm9200_timer_irq = { 89 .name = "at91_tick", 90 .flags = IRQF_SHARED | IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL, 91 .handler = at91rm9200_timer_interrupt 92}; 93 94void at91rm9200_timer_reset(void) 95{ 96 last_crtr = 0; 97 98 /* Real time counter incremented every 30.51758 microseconds */ 99 at91_sys_write(AT91_ST_RTMR, 1); 100 101 /* Set Period Interval timer */ 102 at91_sys_write(AT91_ST_PIMR, LATCH); 103 104 /* Clear any pending interrupts */ 105 (void) at91_sys_read(AT91_ST_SR); 106 107 /* Enable Period Interval Timer interrupt */ 108 at91_sys_write(AT91_ST_IER, AT91_ST_PITS); 109} 110 111/* 112 * Set up timer interrupt. 113 */ 114void __init at91rm9200_timer_init(void) 115{ 116 /* Disable all timer interrupts */ 117 at91_sys_write(AT91_ST_IDR, AT91_ST_PITS | AT91_ST_WDOVF | AT91_ST_RTTINC | AT91_ST_ALMS); 118 (void) at91_sys_read(AT91_ST_SR); /* Clear any pending interrupts */ 119 120 /* Make IRQs happen for the system timer */ 121 setup_irq(AT91_ID_SYS, &at91rm9200_timer_irq); 122 123 /* Change the kernel's 'tick' value to 10009 usec. (the default is 10000) */ 124 tick_usec = (LATCH * 1000000) / CLOCK_TICK_RATE; 125 126 /* Initialize and enable the timer interrupt */ 127 at91rm9200_timer_reset(); 128} 129 130#ifdef CONFIG_PM 131static void at91rm9200_timer_suspend(void) 132{ 133 /* disable Period Interval Timer interrupt */ 134 at91_sys_write(AT91_ST_IDR, AT91_ST_PITS); 135} 136#else 137#define at91rm9200_timer_suspend NULL 138#endif 139 140struct sys_timer at91rm9200_timer = { 141 .init = at91rm9200_timer_init, 142 .offset = at91rm9200_gettimeoffset, 143 .suspend = at91rm9200_timer_suspend, 144 .resume = at91rm9200_timer_reset, 145}; 146