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 static irqreturn_t
  74 pxa_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
  75 {
  76         int next_match;
  77
  78         write_seqlock(&xtime_lock);
  79
  80         /* Loop until we get ahead of the free running timer.
  81          * This ensures an exact clock tick count and time accuracy.
  82          * IRQs are disabled inside the loop to ensure coherence between
  83          * lost_ticks (updated in do_timer()) and the match reg value, so we
  84          * can use do_gettimeofday() from interrupt handlers.
  85          *
  86          * HACK ALERT: it seems that the PXA timer regs aren't updated right
  87          * away in all cases when a write occurs.  We therefore compare with
  88          * 8 instead of 0 in the while() condition below to avoid missing a
  89          * match if OSCR has already reached the next OSMR value.
  90          * Experience has shown that up to 6 ticks are needed to work around
  91          * this problem, but let's use 8 to be conservative.  Note that this
  92          * affect things only when the timer IRQ has been delayed by nearly
  93          * exactly one tick period which should be a pretty rare event.
  94          */
  95         do {
  96                 timer_tick(regs);
  97                 OSSR = OSSR_M0;  /* Clear match on timer 0 */
  98                 next_match = (OSMR0 += LATCH);
  99         } while( (signed long)(next_match - OSCR) <= 8 );
 100
 101         write_sequnlock(&xtime_lock);
 102
 103         return IRQ_HANDLED;
 104 }
 105
 106 static struct irqaction pxa_timer_irq = {
 107         .name           = "PXA Timer Tick",
 108         .flags          = SA_INTERRUPT,
 109         .handler        = pxa_timer_interrupt
 110 };
 111
 112 static void __init pxa_timer_init(void)
 113 {
 114         struct timespec tv;
 115
 116         set_rtc = pxa_set_rtc;
 117
 118         tv.tv_nsec = 0;
 119         tv.tv_sec = pxa_get_rtc_time();
 120         do_settimeofday(&tv);
 121
 122         OSMR0 = 0;              /* set initial match at 0 */
 123         OSSR = 0xf;             /* clear status on all timers */
 124         setup_irq(IRQ_OST0, &pxa_timer_irq);
 125         OIER |= OIER_E0;        /* enable match on timer 0 to cause interrupts */
 126         OSCR = 0;               /* initialize free-running timer, force first match */
 127 }
 128
 129 #ifdef CONFIG_PM
 130 static unsigned long osmr[4], oier;
 131
 132 static void pxa_timer_suspend(void)
 133 {
 134         osmr[0] = OSMR0;
 135         osmr[1] = OSMR1;
 136         osmr[2] = OSMR2;
 137         osmr[3] = OSMR3;
 138         oier = OIER;
 139 }
 140
 141 static void pxa_timer_resume(void)
 142 {
 143         OSMR0 = osmr[0];
 144         OSMR1 = osmr[1];
 145         OSMR2 = osmr[2];
 146         OSMR3 = osmr[3];
 147         OIER = oier;
 148
 149         /*
 150          * OSMR0 is the system timer: make sure OSCR is sufficiently behind
 151          */
 152         OSCR = OSMR0 - LATCH;
 153 }
 154 #else
 155 #define pxa_timer_suspend NULL
 156 #define pxa_timer_resume NULL
 157 #endif
 158
 159 struct sys_timer pxa_timer = {
 160         .init           = pxa_timer_init,
 161         .suspend        = pxa_timer_suspend,
 162         .resume         = pxa_timer_resume,
 163         .offset         = pxa_gettimeoffset,
 164 };