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 int sa1100_set_rtc(void)
  25 {
  26         unsigned long current_time = xtime.tv_sec;
  27
  28         if (RTSR & RTSR_ALE) {
  29                 /* make sure not to forward the clock over an alarm */
  30                 unsigned long alarm = RTAR;
  31                 if (current_time >= alarm && alarm >= RCNR)
  32                         return -ERESTARTSYS;
  33         }
  34         RCNR = current_time;
  35         return 0;
  36 }
  37
  38 /* IRQs are disabled before entering here from do_gettimeofday() */
  39 static unsigned long sa1100_gettimeoffset (void)
  40 {
  41         unsigned long ticks_to_match, elapsed, usec;
  42
  43         /* Get ticks before next timer match */
  44         ticks_to_match = OSMR0 - OSCR;
  45
  46         /* We need elapsed ticks since last match */
  47         elapsed = LATCH - ticks_to_match;
  48
  49         /* Now convert them to usec */
  50         usec = (unsigned long)(elapsed * (tick_nsec / 1000))/LATCH;
  51
  52         return usec;
  53 }
  54
  55 #ifdef CONFIG_NO_IDLE_HZ
  56 static unsigned long initial_match;
  57 static int match_posponed;
  58 #endif
  59
  60 static irqreturn_t
  61 sa1100_timer_interrupt(int irq, void *dev_id)
  62 {
  63         unsigned int next_match;
  64
  65         write_seqlock(&xtime_lock);
  66
  67 #ifdef CONFIG_NO_IDLE_HZ
  68         if (match_posponed) {
  69                 match_posponed = 0;
  70                 OSMR0 = initial_match;
  71         }
  72 #endif
  73
  74         /*
  75          * Loop until we get ahead of the free running timer.
  76          * This ensures an exact clock tick count and time accuracy.
  77          * Since IRQs are disabled at this point, coherence between
  78          * lost_ticks(updated in do_timer()) and the match reg value is
  79          * ensured, hence we can use do_gettimeofday() from interrupt
  80          * handlers.
  81          */
  82         do {
  83                 timer_tick();
  84                 OSSR = OSSR_M0;  /* Clear match on timer 0 */
  85                 next_match = (OSMR0 += LATCH);
  86         } while ((signed long)(next_match - OSCR) <= 0);
  87
  88         write_sequnlock(&xtime_lock);
  89
  90         return IRQ_HANDLED;
  91 }
  92
  93 static struct irqaction sa1100_timer_irq = {
  94         .name           = "SA11xx Timer Tick",
  95         .flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
  96         .handler        = sa1100_timer_interrupt,
  97 };
  98
  99 static void __init sa1100_timer_init(void)
 100 {
 101         unsigned long flags;
 102
 103         set_rtc = sa1100_set_rtc;
 104
 105         OIER = 0;               /* disable any timer interrupts */
 106         OSSR = 0xf;             /* clear status on all timers */
 107         setup_irq(IRQ_OST0, &sa1100_timer_irq);
 108         local_irq_save(flags);
 109         OIER = OIER_E0;         /* enable match on timer 0 to cause interrupts */
 110         OSMR0 = OSCR + LATCH;   /* set initial match */
 111         local_irq_restore(flags);
 112 }
 113
 114 #ifdef CONFIG_NO_IDLE_HZ
 115 static int sa1100_dyn_tick_enable_disable(void)
 116 {
 117         /* nothing to do */
 118         return 0;
 119 }
 120
 121 static void sa1100_dyn_tick_reprogram(unsigned long ticks)
 122 {
 123         if (ticks > 1) {
 124                 initial_match = OSMR0;
 125                 OSMR0 = initial_match + ticks * LATCH;
 126                 match_posponed = 1;
 127         }
 128 }
 129
 130 static irqreturn_t
 131 sa1100_dyn_tick_handler(int irq, void *dev_id)
 132 {
 133         if (match_posponed) {
 134                 match_posponed = 0;
 135                 OSMR0 = initial_match;
 136                 if ((signed long)(initial_match - OSCR) <= 0)
 137                         return sa1100_timer_interrupt(irq, dev_id);
 138         }
 139         return IRQ_NONE;
 140 }
 141
 142 static struct dyn_tick_timer sa1100_dyn_tick = {
 143         .enable         = sa1100_dyn_tick_enable_disable,
 144         .disable        = sa1100_dyn_tick_enable_disable,
 145         .reprogram      = sa1100_dyn_tick_reprogram,
 146         .handler        = sa1100_dyn_tick_handler,
 147 };
 148 #endif
 149
 150 #ifdef CONFIG_PM
 151 unsigned long osmr[4], oier;
 152
 153 static void sa1100_timer_suspend(void)
 154 {
 155         osmr[0] = OSMR0;
 156         osmr[1] = OSMR1;
 157         osmr[2] = OSMR2;
 158         osmr[3] = OSMR3;
 159         oier = OIER;
 160 }
 161
 162 static void sa1100_timer_resume(void)
 163 {
 164         OSSR = 0x0f;
 165         OSMR0 = osmr[0];
 166         OSMR1 = osmr[1];
 167         OSMR2 = osmr[2];
 168         OSMR3 = osmr[3];
 169         OIER = oier;
 170
 171         /*
 172          * OSMR0 is the system timer: make sure OSCR is sufficiently behind
 173          */
 174         OSCR = OSMR0 - LATCH;
 175 }
 176 #else
 177 #define sa1100_timer_suspend NULL
 178 #define sa1100_timer_resume NULL
 179 #endif
 180
 181 struct sys_timer sa1100_timer = {
 182         .init           = sa1100_timer_init,
 183         .suspend        = sa1100_timer_suspend,
 184         .resume         = sa1100_timer_resume,
 185         .offset         = sa1100_gettimeoffset,
 186 #ifdef CONFIG_NO_IDLE_HZ
 187         .dyn_tick       = &sa1100_dyn_tick,
 188 #endif
 189 };