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 #include <linux/clocksource.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 #ifdef CONFIG_NO_IDLE_HZ
  53 static unsigned long initial_match;
  54 static int match_posponed;
  55 #endif
  56
  57 static irqreturn_t
  58 pxa_timer_interrupt(int irq, void *dev_id)
  59 {
  60         int next_match;
  61
  62         write_seqlock(&xtime_lock);
  63
  64 #ifdef CONFIG_NO_IDLE_HZ
  65         if (match_posponed) {
  66                 match_posponed = 0;
  67                 OSMR0 = initial_match;
  68         }
  69 #endif
  70
  71         /* Loop until we get ahead of the free running timer.
  72          * This ensures an exact clock tick count and time accuracy.
  73          * Since IRQs are disabled at this point, coherence between
  74          * lost_ticks(updated in do_timer()) and the match reg value is
  75          * ensured, hence we can use do_gettimeofday() from interrupt
  76          * handlers.
  77          *
  78          * HACK ALERT: it seems that the PXA timer regs aren't updated right
  79          * away in all cases when a write occurs.  We therefore compare with
  80          * 8 instead of 0 in the while() condition below to avoid missing a
  81          * match if OSCR has already reached the next OSMR value.
  82          * Experience has shown that up to 6 ticks are needed to work around
  83          * this problem, but let's use 8 to be conservative.  Note that this
  84          * affect things only when the timer IRQ has been delayed by nearly
  85          * exactly one tick period which should be a pretty rare event.
  86          */
  87         do {
  88                 timer_tick();
  89                 OSSR = OSSR_M0;  /* Clear match on timer 0 */
  90                 next_match = (OSMR0 += LATCH);
  91         } while( (signed long)(next_match - OSCR) <= 8 );
  92
  93         write_sequnlock(&xtime_lock);
  94
  95         return IRQ_HANDLED;
  96 }
  97
  98 static struct irqaction pxa_timer_irq = {
  99         .name           = "PXA Timer Tick",
 100         .flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
 101         .handler        = pxa_timer_interrupt,
 102 };
 103
 104 static cycle_t pxa_get_cycles(void)
 105 {
 106         return OSCR;
 107 }
 108
 109 static struct clocksource clocksource_pxa = {
 110         .name           = "pxa_timer",
 111         .rating         = 200,
 112         .read           = pxa_get_cycles,
 113         .mask           = CLOCKSOURCE_MASK(32),
 114         .shift          = 20,
 115         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 116 };
 117
 118 static void __init pxa_timer_init(void)
 119 {
 120         struct timespec tv;
 121         unsigned long flags;
 122
 123         set_rtc = pxa_set_rtc;
 124
 125         tv.tv_nsec = 0;
 126         tv.tv_sec = pxa_get_rtc_time();
 127         do_settimeofday(&tv);
 128
 129         OIER = 0;               /* disable any timer interrupts */
 130         OSSR = 0xf;             /* clear status on all timers */
 131         setup_irq(IRQ_OST0, &pxa_timer_irq);
 132         local_irq_save(flags);
 133         OIER = OIER_E0;         /* enable match on timer 0 to cause interrupts */
 134         OSMR0 = OSCR + LATCH;   /* set initial match */
 135         local_irq_restore(flags);
 136
 137         /*
 138          * OSCR runs continuously on PXA and is not written to,
 139          * so we can use it as clock source directly.
 140          */
 141         clocksource_pxa.mult =
 142                 clocksource_hz2mult(CLOCK_TICK_RATE, clocksource_pxa.shift);
 143         clocksource_register(&clocksource_pxa);
 144 }
 145
 146 #ifdef CONFIG_NO_IDLE_HZ
 147 static int pxa_dyn_tick_enable_disable(void)
 148 {
 149         /* nothing to do */
 150         return 0;
 151 }
 152
 153 static void pxa_dyn_tick_reprogram(unsigned long ticks)
 154 {
 155         if (ticks > 1) {
 156                 initial_match = OSMR0;
 157                 OSMR0 = initial_match + ticks * LATCH;
 158                 match_posponed = 1;
 159         }
 160 }
 161
 162 static irqreturn_t
 163 pxa_dyn_tick_handler(int irq, void *dev_id)
 164 {
 165         if (match_posponed) {
 166                 match_posponed = 0;
 167                 OSMR0 = initial_match;
 168                 if ( (signed long)(initial_match - OSCR) <= 8 )
 169                         return pxa_timer_interrupt(irq, dev_id);
 170         }
 171         return IRQ_NONE;
 172 }
 173
 174 static struct dyn_tick_timer pxa_dyn_tick = {
 175         .enable         = pxa_dyn_tick_enable_disable,
 176         .disable        = pxa_dyn_tick_enable_disable,
 177         .reprogram      = pxa_dyn_tick_reprogram,
 178         .handler        = pxa_dyn_tick_handler,
 179 };
 180 #endif
 181
 182 #ifdef CONFIG_PM
 183 static unsigned long osmr[4], oier;
 184
 185 static void pxa_timer_suspend(void)
 186 {
 187         osmr[0] = OSMR0;
 188         osmr[1] = OSMR1;
 189         osmr[2] = OSMR2;
 190         osmr[3] = OSMR3;
 191         oier = OIER;
 192 }
 193
 194 static void pxa_timer_resume(void)
 195 {
 196         OSMR0 = osmr[0];
 197         OSMR1 = osmr[1];
 198         OSMR2 = osmr[2];
 199         OSMR3 = osmr[3];
 200         OIER = oier;
 201
 202         /*
 203          * OSMR0 is the system timer: make sure OSCR is sufficiently behind
 204          */
 205         OSCR = OSMR0 - LATCH;
 206 }
 207 #else
 208 #define pxa_timer_suspend NULL
 209 #define pxa_timer_resume NULL
 210 #endif
 211
 212 struct sys_timer pxa_timer = {
 213         .init           = pxa_timer_init,
 214         .suspend        = pxa_timer_suspend,
 215         .resume         = pxa_timer_resume,
 216 #ifdef CONFIG_NO_IDLE_HZ
 217         .dyn_tick       = &pxa_dyn_tick,
 218 #endif
 219 };