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 #include <linux/clocksource.h>
  18
  19 #include <asm/mach/time.h>
  20 #include <asm/hardware.h>
  21
  22 #define RTC_DEF_DIVIDER         (32768 - 1)
  23 #define RTC_DEF_TRIM            0
  24
  25 static int sa1100_set_rtc(void)
  26 {
  27         unsigned long current_time = xtime.tv_sec;
  28
  29         if (RTSR & RTSR_ALE) {
  30                 /* make sure not to forward the clock over an alarm */
  31                 unsigned long alarm = RTAR;
  32                 if (current_time >= alarm && alarm >= RCNR)
  33                         return -ERESTARTSYS;
  34         }
  35         RCNR = current_time;
  36         return 0;
  37 }
  38
  39 #ifdef CONFIG_NO_IDLE_HZ
  40 static unsigned long initial_match;
  41 static int match_posponed;
  42 #endif
  43
  44 static irqreturn_t
  45 sa1100_timer_interrupt(int irq, void *dev_id)
  46 {
  47         unsigned int next_match;
  48
  49 #ifdef CONFIG_NO_IDLE_HZ
  50         if (match_posponed) {
  51                 match_posponed = 0;
  52                 OSMR0 = initial_match;
  53         }
  54 #endif
  55
  56         /*
  57          * Loop until we get ahead of the free running timer.
  58          * This ensures an exact clock tick count and time accuracy.
  59          * Since IRQs are disabled at this point, coherence between
  60          * lost_ticks(updated in do_timer()) and the match reg value is
  61          * ensured, hence we can use do_gettimeofday() from interrupt
  62          * handlers.
  63          */
  64         do {
  65                 timer_tick();
  66                 OSSR = OSSR_M0;  /* Clear match on timer 0 */
  67                 next_match = (OSMR0 += LATCH);
  68         } while ((signed long)(next_match - OSCR) <= 0);
  69
  70         return IRQ_HANDLED;
  71 }
  72
  73 static struct irqaction sa1100_timer_irq = {
  74         .name           = "SA11xx Timer Tick",
  75         .flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
  76         .handler        = sa1100_timer_interrupt,
  77 };
  78
  79 static cycle_t sa1100_read_oscr(void)
  80 {
  81         return OSCR;
  82 }
  83
  84 static struct clocksource cksrc_sa1100_oscr = {
  85         .name           = "oscr",
  86         .rating         = 200,
  87         .read           = sa1100_read_oscr,
  88         .mask           = CLOCKSOURCE_MASK(32),
  89         .shift          = 20,
  90         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  91 };
  92
  93 static void __init sa1100_timer_init(void)
  94 {
  95         unsigned long flags;
  96
  97         set_rtc = sa1100_set_rtc;
  98
  99         OIER = 0;               /* disable any timer interrupts */
 100         OSSR = 0xf;             /* clear status on all timers */
 101         setup_irq(IRQ_OST0, &sa1100_timer_irq);
 102         local_irq_save(flags);
 103         OIER = OIER_E0;         /* enable match on timer 0 to cause interrupts */
 104         OSMR0 = OSCR + LATCH;   /* set initial match */
 105         local_irq_restore(flags);
 106
 107         cksrc_sa1100_oscr.mult =
 108                 clocksource_hz2mult(CLOCK_TICK_RATE, cksrc_sa1100_oscr.shift);
 109
 110         clocksource_register(&cksrc_sa1100_oscr);
 111 }
 112
 113 #ifdef CONFIG_NO_IDLE_HZ
 114 static int sa1100_dyn_tick_enable_disable(void)
 115 {
 116         /* nothing to do */
 117         return 0;
 118 }
 119
 120 static void sa1100_dyn_tick_reprogram(unsigned long ticks)
 121 {
 122         if (ticks > 1) {
 123                 initial_match = OSMR0;
 124                 OSMR0 = initial_match + ticks * LATCH;
 125                 match_posponed = 1;
 126         }
 127 }
 128
 129 static irqreturn_t
 130 sa1100_dyn_tick_handler(int irq, void *dev_id)
 131 {
 132         if (match_posponed) {
 133                 match_posponed = 0;
 134                 OSMR0 = initial_match;
 135                 if ((signed long)(initial_match - OSCR) <= 0)
 136                         return sa1100_timer_interrupt(irq, dev_id);
 137         }
 138         return IRQ_NONE;
 139 }
 140
 141 static struct dyn_tick_timer sa1100_dyn_tick = {
 142         .enable         = sa1100_dyn_tick_enable_disable,
 143         .disable        = sa1100_dyn_tick_enable_disable,
 144         .reprogram      = sa1100_dyn_tick_reprogram,
 145         .handler        = sa1100_dyn_tick_handler,
 146 };
 147 #endif
 148
 149 #ifdef CONFIG_PM
 150 unsigned long osmr[4], oier;
 151
 152 static void sa1100_timer_suspend(void)
 153 {
 154         osmr[0] = OSMR0;
 155         osmr[1] = OSMR1;
 156         osmr[2] = OSMR2;
 157         osmr[3] = OSMR3;
 158         oier = OIER;
 159 }
 160
 161 static void sa1100_timer_resume(void)
 162 {
 163         OSSR = 0x0f;
 164         OSMR0 = osmr[0];
 165         OSMR1 = osmr[1];
 166         OSMR2 = osmr[2];
 167         OSMR3 = osmr[3];
 168         OIER = oier;
 169
 170         /*
 171          * OSMR0 is the system timer: make sure OSCR is sufficiently behind
 172          */
 173         OSCR = OSMR0 - LATCH;
 174 }
 175 #else
 176 #define sa1100_timer_suspend NULL
 177 #define sa1100_timer_resume NULL
 178 #endif
 179
 180 struct sys_timer sa1100_timer = {
 181         .init           = sa1100_timer_init,
 182         .suspend        = sa1100_timer_suspend,
 183         .resume         = sa1100_timer_resume,
 184 #ifdef CONFIG_NO_IDLE_HZ
 185         .dyn_tick       = &sa1100_dyn_tick,
 186 #endif
 187 };