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/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
  24 static 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 diviser 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
  43 static 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() */
  58 static 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
  75 static unsigned long initial_match;
  76 static int match_posponed;
  77 #endif
  78
  79 static irqreturn_t
  80 sa1100_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
 112 static struct irqaction sa1100_timer_irq = {
 113         .name           = "SA11xx Timer Tick",
 114         .flags          = IRQF_DISABLED | IRQF_TIMER,
 115         .handler        = sa1100_timer_interrupt,
 116 };
 117
 118 static void __init sa1100_timer_init(void)
 119 {
 120         struct timespec tv;
 121
 122         set_rtc = sa1100_set_rtc;
 123
 124         tv.tv_nsec = 0;
 125         tv.tv_sec = sa1100_get_rtc_time();
 126         do_settimeofday(&tv);
 127
 128         OIER = 0;               /* disable any timer interrupts */
 129         OSCR = LATCH*2;         /* push OSCR out of the way */
 130         OSMR0 = LATCH;          /* set initial match */
 131         OSSR = 0xf;             /* clear status on all timers */
 132         setup_irq(IRQ_OST0, &sa1100_timer_irq);
 133         OIER = OIER_E0;         /* enable match on timer 0 to cause interrupts */
 134         OSCR = 0;               /* initialize free-running timer */
 135 }
 136
 137 #ifdef CONFIG_NO_IDLE_HZ
 138 static int sa1100_dyn_tick_enable_disable(void)
 139 {
 140         /* nothing to do */
 141         return 0;
 142 }
 143
 144 static void sa1100_dyn_tick_reprogram(unsigned long ticks)
 145 {
 146         if (ticks > 1) {
 147                 initial_match = OSMR0;
 148                 OSMR0 = initial_match + ticks * LATCH;
 149                 match_posponed = 1;
 150         }
 151 }
 152
 153 static irqreturn_t
 154 sa1100_dyn_tick_handler(int irq, void *dev_id)
 155 {
 156         if (match_posponed) {
 157                 match_posponed = 0;
 158                 OSMR0 = initial_match;
 159                 if ((signed long)(initial_match - OSCR) <= 0)
 160                         return sa1100_timer_interrupt(irq, dev_id);
 161         }
 162         return IRQ_NONE;
 163 }
 164
 165 static struct dyn_tick_timer sa1100_dyn_tick = {
 166         .enable         = sa1100_dyn_tick_enable_disable,
 167         .disable        = sa1100_dyn_tick_enable_disable,
 168         .reprogram      = sa1100_dyn_tick_reprogram,
 169         .handler        = sa1100_dyn_tick_handler,
 170 };
 171 #endif
 172
 173 #ifdef CONFIG_PM
 174 unsigned long osmr[4], oier;
 175
 176 static void sa1100_timer_suspend(void)
 177 {
 178         osmr[0] = OSMR0;
 179         osmr[1] = OSMR1;
 180         osmr[2] = OSMR2;
 181         osmr[3] = OSMR3;
 182         oier = OIER;
 183 }
 184
 185 static void sa1100_timer_resume(void)
 186 {
 187         OSSR = 0x0f;
 188         OSMR0 = osmr[0];
 189         OSMR1 = osmr[1];
 190         OSMR2 = osmr[2];
 191         OSMR3 = osmr[3];
 192         OIER = oier;
 193
 194         /*
 195          * OSMR0 is the system timer: make sure OSCR is sufficiently behind
 196          */
 197         OSCR = OSMR0 - LATCH;
 198 }
 199 #else
 200 #define sa1100_timer_suspend NULL
 201 #define sa1100_timer_resume NULL
 202 #endif
 203
 204 struct sys_timer sa1100_timer = {
 205         .init           = sa1100_timer_init,
 206         .suspend        = sa1100_timer_suspend,
 207         .resume         = sa1100_timer_resume,
 208         .offset         = sa1100_gettimeoffset,
 209 #ifdef CONFIG_NO_IDLE_HZ
 210         .dyn_tick       = &sa1100_dyn_tick,
 211 #endif
 212 };