arch/arm/mach-sa1100/time.c

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