1/* 2 * linux/arch/arm/mach-sa1100/time.c 3 * 4 * Copyright (C) 1998 Deborah Wallach. 5 * Twiddles (C) 1999 Hugo Fiennes <hugo@empeg.com> 6 * 7 * 2000/03/29 (C) Nicolas Pitre <nico@cam.org> 8 * Rewritten: big cleanup, much simpler, better HZ accuracy. 9 * 10 */ 11#include <linux/init.h> 12#include <linux/errno.h> 13#include <linux/interrupt.h> 14#include <linux/irq.h> 15#include <linux/timex.h> 16#include <linux/signal.h> 17 18#include <asm/mach/time.h> 19#include <asm/hardware.h> 20 21#define RTC_DEF_DIVIDER (32768 - 1) 22#define RTC_DEF_TRIM 0 23 24static unsigned long __init sa1100_get_rtc_time(void) 25{ 26 /* 27 * According to the manual we should be able to let RTTR be zero 28 * and then a default divisor for a 32.768KHz clock is used. 29 * Apparently this doesn't work, at least for my SA1110 rev 5. 30 * If the clock divider is uninitialized then reset it to the 31 * default value to get the 1Hz clock. 32 */ 33 if (RTTR == 0) { 34 RTTR = RTC_DEF_DIVIDER + (RTC_DEF_TRIM << 16); 35 printk(KERN_WARNING "Warning: uninitialized Real Time Clock\n"); 36 /* The current RTC value probably doesn't make sense either */ 37 RCNR = 0; 38 return 0; 39 } 40 return RCNR; 41} 42 43static int sa1100_set_rtc(void) 44{ 45 unsigned long current_time = xtime.tv_sec; 46 47 if (RTSR & RTSR_ALE) { 48 /* make sure not to forward the clock over an alarm */ 49 unsigned long alarm = RTAR; 50 if (current_time >= alarm && alarm >= RCNR) 51 return -ERESTARTSYS; 52 } 53 RCNR = current_time; 54 return 0; 55} 56 57/* IRQs are disabled before entering here from do_gettimeofday() */ 58static unsigned long sa1100_gettimeoffset (void) 59{ 60 unsigned long ticks_to_match, elapsed, usec; 61 62 /* Get ticks before next timer match */ 63 ticks_to_match = OSMR0 - OSCR; 64 65 /* We need elapsed ticks since last match */ 66 elapsed = LATCH - ticks_to_match; 67 68 /* Now convert them to usec */ 69 usec = (unsigned long)(elapsed * (tick_nsec / 1000))/LATCH; 70 71 return usec; 72} 73 74#ifdef CONFIG_NO_IDLE_HZ 75static unsigned long initial_match; 76static int match_posponed; 77#endif 78 79static irqreturn_t 80sa1100_timer_interrupt(int irq, void *dev_id) 81{ 82 unsigned int next_match; 83 84 write_seqlock(&xtime_lock); 85 86#ifdef CONFIG_NO_IDLE_HZ 87 if (match_posponed) { 88 match_posponed = 0; 89 OSMR0 = initial_match; 90 } 91#endif 92 93 /* 94 * Loop until we get ahead of the free running timer. 95 * This ensures an exact clock tick count and time accuracy. 96 * Since IRQs are disabled at this point, coherence between 97 * lost_ticks(updated in do_timer()) and the match reg value is 98 * ensured, hence we can use do_gettimeofday() from interrupt 99 * handlers. 100 */ 101 do { 102 timer_tick(); 103 OSSR = OSSR_M0; /* Clear match on timer 0 */ 104 next_match = (OSMR0 += LATCH); 105 } while ((signed long)(next_match - OSCR) <= 0); 106 107 write_sequnlock(&xtime_lock); 108 109 return IRQ_HANDLED; 110} 111 112static struct irqaction sa1100_timer_irq = { 113 .name = "SA11xx Timer Tick", 114 .flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL, 115 .handler = sa1100_timer_interrupt, 116}; 117 118static void __init sa1100_timer_init(void) 119{ 120 struct timespec tv; 121 unsigned long flags; 122 123 set_rtc = sa1100_set_rtc; 124 125 tv.tv_nsec = 0; 126 tv.tv_sec = sa1100_get_rtc_time(); 127 do_settimeofday(&tv); 128 129 OIER = 0; /* disable any timer interrupts */ 130 OSSR = 0xf; /* clear status on all timers */ 131 setup_irq(IRQ_OST0, &sa1100_timer_irq); 132 local_irq_save(flags); 133 OIER = OIER_E0; /* enable match on timer 0 to cause interrupts */ 134 OSMR0 = OSCR + LATCH; /* set initial match */ 135 local_irq_restore(flags); 136} 137 138#ifdef CONFIG_NO_IDLE_HZ 139static int sa1100_dyn_tick_enable_disable(void) 140{ 141 /* nothing to do */ 142 return 0; 143} 144 145static void sa1100_dyn_tick_reprogram(unsigned long ticks) 146{ 147 if (ticks > 1) { 148 initial_match = OSMR0; 149 OSMR0 = initial_match + ticks * LATCH; 150 match_posponed = 1; 151 } 152} 153 154static irqreturn_t 155sa1100_dyn_tick_handler(int irq, void *dev_id) 156{ 157 if (match_posponed) { 158 match_posponed = 0; 159 OSMR0 = initial_match; 160 if ((signed long)(initial_match - OSCR) <= 0) 161 return sa1100_timer_interrupt(irq, dev_id); 162 } 163 return IRQ_NONE; 164} 165 166static struct dyn_tick_timer sa1100_dyn_tick = { 167 .enable = sa1100_dyn_tick_enable_disable, 168 .disable = sa1100_dyn_tick_enable_disable, 169 .reprogram = sa1100_dyn_tick_reprogram, 170 .handler = sa1100_dyn_tick_handler, 171}; 172#endif 173 174#ifdef CONFIG_PM 175unsigned long osmr[4], oier; 176 177static void sa1100_timer_suspend(void) 178{ 179 osmr[0] = OSMR0; 180 osmr[1] = OSMR1; 181 osmr[2] = OSMR2; 182 osmr[3] = OSMR3; 183 oier = OIER; 184} 185 186static void sa1100_timer_resume(void) 187{ 188 OSSR = 0x0f; 189 OSMR0 = osmr[0]; 190 OSMR1 = osmr[1]; 191 OSMR2 = osmr[2]; 192 OSMR3 = osmr[3]; 193 OIER = oier; 194 195 /* 196 * OSMR0 is the system timer: make sure OSCR is sufficiently behind 197 */ 198 OSCR = OSMR0 - LATCH; 199} 200#else 201#define sa1100_timer_suspend NULL 202#define sa1100_timer_resume NULL 203#endif 204 205struct sys_timer sa1100_timer = { 206 .init = sa1100_timer_init, 207 .suspend = sa1100_timer_suspend, 208 .resume = sa1100_timer_resume, 209 .offset = sa1100_gettimeoffset, 210#ifdef CONFIG_NO_IDLE_HZ 211 .dyn_tick = &sa1100_dyn_tick, 212#endif 213}; 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