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/config.h>
  14 #include <linux/kernel.h>
  15 #include <linux/init.h>
  16 #include <linux/delay.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/time.h>
  19 #include <linux/signal.h>
  20 #include <linux/errno.h>
  21 #include <linux/sched.h>
  22
  23 #include <asm/system.h>
  24 #include <asm/hardware.h>
  25 #include <asm/io.h>
  26 #include <asm/leds.h>
  27 #include <asm/irq.h>
  28 #include <asm/mach/irq.h>
  29 #include <asm/mach/time.h>
  30 #include <asm/arch/pxa-regs.h>
  31
  32
  33 static inline unsigned long pxa_get_rtc_time(void)
  34 {
  35         return RCNR;
  36 }
  37
  38 static int pxa_set_rtc(void)
  39 {
  40         unsigned long current_time = xtime.tv_sec;
  41
  42         if (RTSR & RTSR_ALE) {
  43                 /* make sure not to forward the clock over an alarm */
  44                 unsigned long alarm = RTAR;
  45                 if (current_time >= alarm && alarm >= RCNR)
  46                         return -ERESTARTSYS;
  47         }
  48         RCNR = current_time;
  49         return 0;
  50 }
  51
  52 /* IRQs are disabled before entering here from do_gettimeofday() */
  53 static unsigned long pxa_gettimeoffset (void)
  54 {
  55         long ticks_to_match, elapsed, usec;
  56
  57         /* Get ticks before next timer match */
  58         ticks_to_match = OSMR0 - OSCR;
  59
  60         /* We need elapsed ticks since last match */
  61         elapsed = LATCH - ticks_to_match;
  62
  63         /* don't get fooled by the workaround in pxa_timer_interrupt() */
  64         if (elapsed <= 0)
  65                 return 0;
  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 pxa_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
  80 {
  81         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         /* Loop until we get ahead of the free running timer.
  93          * This ensures an exact clock tick count and time accuracy.
  94          * Since IRQs are disabled at this point, coherence between
  95          * lost_ticks(updated in do_timer()) and the match reg value is
  96          * ensured, hence we can use do_gettimeofday() from interrupt
  97          * handlers.
  98          *
  99          * HACK ALERT: it seems that the PXA timer regs aren't updated right
 100          * away in all cases when a write occurs.  We therefore compare with
 101          * 8 instead of 0 in the while() condition below to avoid missing a
 102          * match if OSCR has already reached the next OSMR value.
 103          * Experience has shown that up to 6 ticks are needed to work around
 104          * this problem, but let's use 8 to be conservative.  Note that this
 105          * affect things only when the timer IRQ has been delayed by nearly
 106          * exactly one tick period which should be a pretty rare event.
 107          */
 108         do {
 109                 timer_tick(regs);
 110                 OSSR = OSSR_M0;  /* Clear match on timer 0 */
 111                 next_match = (OSMR0 += LATCH);
 112         } while( (signed long)(next_match - OSCR) <= 8 );
 113
 114         write_sequnlock(&xtime_lock);
 115
 116         return IRQ_HANDLED;
 117 }
 118
 119 static struct irqaction pxa_timer_irq = {
 120         .name           = "PXA Timer Tick",
 121         .flags          = SA_INTERRUPT | SA_TIMER,
 122         .handler        = pxa_timer_interrupt,
 123 };
 124
 125 static void __init pxa_timer_init(void)
 126 {
 127         struct timespec tv;
 128
 129         set_rtc = pxa_set_rtc;
 130
 131         tv.tv_nsec = 0;
 132         tv.tv_sec = pxa_get_rtc_time();
 133         do_settimeofday(&tv);
 134
 135         OIER = 0;               /* disable any timer interrupts */
 136         OSCR = LATCH*2;         /* push OSCR out of the way */
 137         OSMR0 = LATCH;          /* set initial match */
 138         OSSR = 0xf;             /* clear status on all timers */
 139         setup_irq(IRQ_OST0, &pxa_timer_irq);
 140         OIER = OIER_E0;         /* enable match on timer 0 to cause interrupts */
 141         OSCR = 0;               /* initialize free-running timer */
 142 }
 143
 144 #ifdef CONFIG_NO_IDLE_HZ
 145 static int pxa_dyn_tick_enable_disable(void)
 146 {
 147         /* nothing to do */
 148         return 0;
 149 }
 150
 151 static void pxa_dyn_tick_reprogram(unsigned long ticks)
 152 {
 153         if (ticks > 1) {
 154                 initial_match = OSMR0;
 155                 OSMR0 = initial_match + ticks * LATCH;
 156                 match_posponed = 1;
 157         }
 158 }
 159
 160 static irqreturn_t
 161 pxa_dyn_tick_handler(int irq, void *dev_id, struct pt_regs *regs)
 162 {
 163         if (match_posponed) {
 164                 match_posponed = 0;
 165                 OSMR0 = initial_match;
 166                 if ( (signed long)(initial_match - OSCR) <= 8 )
 167                         return pxa_timer_interrupt(irq, dev_id, regs);
 168         }
 169         return IRQ_NONE;
 170 }
 171
 172 static struct dyn_tick_timer pxa_dyn_tick = {
 173         .enable         = pxa_dyn_tick_enable_disable,
 174         .disable        = pxa_dyn_tick_enable_disable,
 175         .reprogram      = pxa_dyn_tick_reprogram,
 176         .handler        = pxa_dyn_tick_handler,
 177 };
 178 #endif
 179
 180 #ifdef CONFIG_PM
 181 static unsigned long osmr[4], oier;
 182
 183 static void pxa_timer_suspend(void)
 184 {
 185         osmr[0] = OSMR0;
 186         osmr[1] = OSMR1;
 187         osmr[2] = OSMR2;
 188         osmr[3] = OSMR3;
 189         oier = OIER;
 190 }
 191
 192 static void pxa_timer_resume(void)
 193 {
 194         OSMR0 = osmr[0];
 195         OSMR1 = osmr[1];
 196         OSMR2 = osmr[2];
 197         OSMR3 = osmr[3];
 198         OIER = oier;
 199
 200         /*
 201          * OSMR0 is the system timer: make sure OSCR is sufficiently behind
 202          */
 203         OSCR = OSMR0 - LATCH;
 204 }
 205 #else
 206 #define pxa_timer_suspend NULL
 207 #define pxa_timer_resume NULL
 208 #endif
 209
 210 struct sys_timer pxa_timer = {
 211         .init           = pxa_timer_init,
 212         .suspend        = pxa_timer_suspend,
 213         .resume         = pxa_timer_resume,
 214         .offset         = pxa_gettimeoffset,
 215 #ifdef CONFIG_NO_IDLE_HZ
 216         .dyn_tick       = &pxa_dyn_tick,
 217 #endif
 218 };