arch/arm/mach-pxa/time.c

   1 /*
   2  * arch/arm/mach-pxa/time.c
   3  *
   4  * Author:      Nicolas Pitre
   5  * Created:     Jun 15, 2001
   6  * Copyright:   MontaVista Software Inc.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/kernel.h>
  14 #include <linux/init.h>
  15 #include <linux/delay.h>
  16 #include <linux/interrupt.h>
  17 #include <linux/time.h>
  18 #include <linux/signal.h>
  19 #include <linux/errno.h>
  20 #include <linux/sched.h>
  21
  22 #include <asm/system.h>
  23 #include <asm/hardware.h>
  24 #include <asm/io.h>
  25 #include <asm/leds.h>
  26 #include <asm/irq.h>
  27 #include <asm/mach/irq.h>
  28 #include <asm/mach/time.h>
  29 #include <asm/arch/pxa-regs.h>
  30
  31
  32 static inline unsigned long pxa_get_rtc_time(void)
  33 {
  34         return RCNR;
  35 }
  36
  37 static int pxa_set_rtc(void)
  38 {
  39         unsigned long current_time = xtime.tv_sec;
  40
  41         if (RTSR & RTSR_ALE) {
  42                 /* make sure not to forward the clock over an alarm */
  43                 unsigned long alarm = RTAR;
  44                 if (current_time >= alarm && alarm >= RCNR)
  45                         return -ERESTARTSYS;
  46         }
  47         RCNR = current_time;
  48         return 0;
  49 }
  50
  51 /* IRQs are disabled before entering here from do_gettimeofday() */
  52 static unsigned long pxa_gettimeoffset (void)
  53 {
  54         long ticks_to_match, elapsed, usec;
  55
  56         /* Get ticks before next timer match */
  57         ticks_to_match = OSMR0 - OSCR;
  58
  59         /* We need elapsed ticks since last match */
  60         elapsed = LATCH - ticks_to_match;
  61
  62         /* don't get fooled by the workaround in pxa_timer_interrupt() */
  63         if (elapsed <= 0)
  64                 return 0;
  65
  66         /* Now convert them to usec */
  67         usec = (unsigned long)(elapsed * (tick_nsec / 1000))/LATCH;
  68
  69         return usec;
  70 }
  71
  72 #ifdef CONFIG_NO_IDLE_HZ
  73 static unsigned long initial_match;
  74 static int match_posponed;
  75 #endif
  76
  77 static irqreturn_t
  78 pxa_timer_interrupt(int irq, void *dev_id)
  79 {
  80         int next_match;
  81
  82         write_seqlock(&xtime_lock);
  83
  84 #ifdef CONFIG_NO_IDLE_HZ
  85         if (match_posponed) {
  86                 match_posponed = 0;
  87                 OSMR0 = initial_match;
  88         }
  89 #endif
  90
  91         /* Loop until we get ahead of the free running timer.
  92          * This ensures an exact clock tick count and time accuracy.
  93          * Since IRQs are disabled at this point, coherence between
  94          * lost_ticks(updated in do_timer()) and the match reg value is
  95          * ensured, hence we can use do_gettimeofday() from interrupt
  96          * handlers.
  97          *
  98          * HACK ALERT: it seems that the PXA timer regs aren't updated right
  99          * away in all cases when a write occurs.  We therefore compare with
 100          * 8 instead of 0 in the while() condition below to avoid missing a
 101          * match if OSCR has already reached the next OSMR value.
 102          * Experience has shown that up to 6 ticks are needed to work around
 103          * this problem, but let's use 8 to be conservative.  Note that this
 104          * affect things only when the timer IRQ has been delayed by nearly
 105          * exactly one tick period which should be a pretty rare event.
 106          */
 107         do {
 108                 timer_tick();
 109                 OSSR = OSSR_M0;  /* Clear match on timer 0 */
 110                 next_match = (OSMR0 += LATCH);
 111         } while( (signed long)(next_match - OSCR) <= 8 );
 112
 113         write_sequnlock(&xtime_lock);
 114
 115         return IRQ_HANDLED;
 116 }
 117
 118 static struct irqaction pxa_timer_irq = {
 119         .name           = "PXA Timer Tick",
 120         .flags          = IRQF_DISABLED | IRQF_TIMER,
 121         .handler        = pxa_timer_interrupt,
 122 };
 123
 124 static void __init pxa_timer_init(void)
 125 {
 126         struct timespec tv;
 127
 128         set_rtc = pxa_set_rtc;
 129
 130         tv.tv_nsec = 0;
 131         tv.tv_sec = pxa_get_rtc_time();
 132         do_settimeofday(&tv);
 133
 134         OIER = 0;               /* disable any timer interrupts */
 135         OSCR = LATCH*2;         /* push OSCR out of the way */
 136         OSMR0 = LATCH;          /* set initial match */
 137         OSSR = 0xf;             /* clear status on all timers */
 138         setup_irq(IRQ_OST0, &pxa_timer_irq);
 139         OIER = OIER_E0;         /* enable match on timer 0 to cause interrupts */
 140         OSCR = 0;               /* initialize free-running timer */
 141 }
 142
 143 #ifdef CONFIG_NO_IDLE_HZ
 144 static int pxa_dyn_tick_enable_disable(void)
 145 {
 146         /* nothing to do */
 147         return 0;
 148 }
 149
 150 static void pxa_dyn_tick_reprogram(unsigned long ticks)
 151 {
 152         if (ticks > 1) {
 153                 initial_match = OSMR0;
 154                 OSMR0 = initial_match + ticks * LATCH;
 155                 match_posponed = 1;
 156         }
 157 }
 158
 159 static irqreturn_t
 160 pxa_dyn_tick_handler(int irq, void *dev_id)
 161 {
 162         if (match_posponed) {
 163                 match_posponed = 0;
 164                 OSMR0 = initial_match;
 165                 if ( (signed long)(initial_match - OSCR) <= 8 )
 166                         return pxa_timer_interrupt(irq, dev_id);
 167         }
 168         return IRQ_NONE;
 169 }
 170
 171 static struct dyn_tick_timer pxa_dyn_tick = {
 172         .enable         = pxa_dyn_tick_enable_disable,
 173         .disable        = pxa_dyn_tick_enable_disable,
 174         .reprogram      = pxa_dyn_tick_reprogram,
 175         .handler        = pxa_dyn_tick_handler,
 176 };
 177 #endif
 178
 179 #ifdef CONFIG_PM
 180 static unsigned long osmr[4], oier;
 181
 182 static void pxa_timer_suspend(void)
 183 {
 184         osmr[0] = OSMR0;
 185         osmr[1] = OSMR1;
 186         osmr[2] = OSMR2;
 187         osmr[3] = OSMR3;
 188         oier = OIER;
 189 }
 190
 191 static void pxa_timer_resume(void)
 192 {
 193         OSMR0 = osmr[0];
 194         OSMR1 = osmr[1];
 195         OSMR2 = osmr[2];
 196         OSMR3 = osmr[3];
 197         OIER = oier;
 198
 199         /*
 200          * OSMR0 is the system timer: make sure OSCR is sufficiently behind
 201          */
 202         OSCR = OSMR0 - LATCH;
 203 }
 204 #else
 205 #define pxa_timer_suspend NULL
 206 #define pxa_timer_resume NULL
 207 #endif
 208
 209 struct sys_timer pxa_timer = {
 210         .init           = pxa_timer_init,
 211         .suspend        = pxa_timer_suspend,
 212         .resume         = pxa_timer_resume,
 213         .offset         = pxa_gettimeoffset,
 214 #ifdef CONFIG_NO_IDLE_HZ
 215         .dyn_tick       = &pxa_dyn_tick,
 216 #endif
 217 };