hw/ptimer.c

   1 /*
   2  * General purpose implementation of a simple periodic countdown timer.
   3  *
   4  * Copyright (c) 2007 CodeSourcery.
   5  *
   6  * This code is licenced under the GNU LGPL.
   7  */
   8 #include "hw.h"
   9 #include "qemu-timer.h"
  10
  11
  12 struct ptimer_state
  13 {
  14     int enabled; /* 0 = disabled, 1 = periodic, 2 = oneshot.  */
  15     uint64_t limit;
  16     uint64_t delta;
  17     uint32_t period_frac;
  18     int64_t period;
  19     int64_t last_event;
  20     int64_t next_event;
  21     QEMUBH *bh;
  22     QEMUTimer *timer;
  23 };
  24
  25 /* Use a bottom-half routine to avoid reentrancy issues.  */
  26 static void ptimer_trigger(ptimer_state *s)
  27 {
  28     if (s->bh) {
  29         qemu_bh_schedule(s->bh);
  30     }
  31 }
  32
  33 static void ptimer_reload(ptimer_state *s)
  34 {
  35     if (s->delta == 0) {
  36         ptimer_trigger(s);
  37         s->delta = s->limit;
  38     }
  39     if (s->delta == 0 || s->period == 0) {
  40         fprintf(stderr, "Timer with period zero, disabling\n");
  41         s->enabled = 0;
  42         return;
  43     }
  44
  45     s->last_event = s->next_event;
  46     s->next_event = s->last_event + s->delta * s->period;
  47     if (s->period_frac) {
  48         s->next_event += ((int64_t)s->period_frac * s->delta) >> 32;
  49     }
  50     qemu_mod_timer(s->timer, s->next_event);
  51 }
  52
  53 static void ptimer_tick(void *opaque)
  54 {
  55     ptimer_state *s = (ptimer_state *)opaque;
  56     ptimer_trigger(s);
  57     s->delta = 0;
  58     if (s->enabled == 2) {
  59         s->enabled = 0;
  60     } else {
  61         ptimer_reload(s);
  62     }
  63 }
  64
  65 uint64_t ptimer_get_count(ptimer_state *s)
  66 {
  67     int64_t now;
  68     uint64_t counter;
  69
  70     if (s->enabled) {
  71         now = qemu_get_clock(vm_clock);
  72         /* Figure out the current counter value.  */
  73         if (now - s->next_event > 0
  74             || s->period == 0) {
  75             /* Prevent timer underflowing if it should already have
  76                triggered.  */
  77             counter = 0;
  78         } else {
  79             uint64_t rem;
  80             uint64_t div;
  81
  82             rem = s->next_event - now;
  83             div = s->period;
  84             counter = rem / div;
  85         }
  86     } else {
  87         counter = s->delta;
  88     }
  89     return counter;
  90 }
  91
  92 void ptimer_set_count(ptimer_state *s, uint64_t count)
  93 {
  94     s->delta = count;
  95     if (s->enabled) {
  96         s->next_event = qemu_get_clock(vm_clock);
  97         ptimer_reload(s);
  98     }
  99 }
 100
 101 void ptimer_run(ptimer_state *s, int oneshot)
 102 {
 103     if (s->enabled) {
 104         return;
 105     }
 106     if (s->period == 0) {
 107         fprintf(stderr, "Timer with period zero, disabling\n");
 108         return;
 109     }
 110     s->enabled = oneshot ? 2 : 1;
 111     s->next_event = qemu_get_clock(vm_clock);
 112     ptimer_reload(s);
 113 }
 114
 115 /* Pause a timer.  Note that this may cause it to "lose" time, even if it
 116    is immediately restarted.  */
 117 void ptimer_stop(ptimer_state *s)
 118 {
 119     if (!s->enabled)
 120         return;
 121
 122     s->delta = ptimer_get_count(s);
 123     qemu_del_timer(s->timer);
 124     s->enabled = 0;
 125 }
 126
 127 /* Set counter increment interval in nanoseconds.  */
 128 void ptimer_set_period(ptimer_state *s, int64_t period)
 129 {
 130     s->period = period;
 131     s->period_frac = 0;
 132     if (s->enabled) {
 133         s->next_event = qemu_get_clock(vm_clock);
 134         ptimer_reload(s);
 135     }
 136 }
 137
 138 /* Set counter frequency in Hz.  */
 139 void ptimer_set_freq(ptimer_state *s, uint32_t freq)
 140 {
 141     s->period = 1000000000ll / freq;
 142     s->period_frac = (1000000000ll << 32) / freq;
 143     if (s->enabled) {
 144         s->next_event = qemu_get_clock(vm_clock);
 145         ptimer_reload(s);
 146     }
 147 }
 148
 149 /* Set the initial countdown value.  If reload is nonzero then also set
 150    count = limit.  */
 151 void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload)
 152 {
 153     s->limit = limit;
 154     if (reload)
 155         s->delta = limit;
 156     if (s->enabled && reload) {
 157         s->next_event = qemu_get_clock(vm_clock);
 158         ptimer_reload(s);
 159     }
 160 }
 161
 162 void qemu_put_ptimer(QEMUFile *f, ptimer_state *s)
 163 {
 164     qemu_put_byte(f, s->enabled);
 165     qemu_put_be64s(f, &s->limit);
 166     qemu_put_be64s(f, &s->delta);
 167     qemu_put_be32s(f, &s->period_frac);
 168     qemu_put_be64s(f, &s->period);
 169     qemu_put_be64s(f, &s->last_event);
 170     qemu_put_be64s(f, &s->next_event);
 171     qemu_put_timer(f, s->timer);
 172 }
 173
 174 void qemu_get_ptimer(QEMUFile *f, ptimer_state *s)
 175 {
 176     s->enabled = qemu_get_byte(f);
 177     qemu_get_be64s(f, &s->limit);
 178     qemu_get_be64s(f, &s->delta);
 179     qemu_get_be32s(f, &s->period_frac);
 180     qemu_get_be64s(f, &s->period);
 181     qemu_get_be64s(f, &s->last_event);
 182     qemu_get_be64s(f, &s->next_event);
 183     qemu_get_timer(f, s->timer);
 184 }
 185
 186 ptimer_state *ptimer_init(QEMUBH *bh)
 187 {
 188     ptimer_state *s;
 189
 190     s = (ptimer_state *)qemu_mallocz(sizeof(ptimer_state));
 191     s->bh = bh;
 192     s->timer = qemu_new_timer(vm_clock, ptimer_tick, s);
 193     return s;
 194 }
 195