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* High Precisition Event Timer emulation
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* Copyright (c) 2007 Alexander Graf
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* Copyright (c) 2008 IBM Corporation
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* Authors: Beth Kon <bkon@us.ibm.com>
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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* *****************************************************************
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* This driver attempts to emulate an HPET device in software.
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#include "qemu-timer.h"
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#include "hpet_emul.h"
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#define dprintf printf
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static HPETState *hpet_statep;
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uint32_t hpet_in_legacy_mode(void)
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return hpet_statep->config & HPET_CFG_LEGACY;
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static uint32_t timer_int_route(struct HPETTimer *timer)
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route = (timer->config & HPET_TN_INT_ROUTE_MASK) >> HPET_TN_INT_ROUTE_SHIFT;
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static uint32_t hpet_enabled(void)
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return hpet_statep->config & HPET_CFG_ENABLE;
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static uint32_t timer_is_periodic(HPETTimer *t)
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return t->config & HPET_TN_PERIODIC;
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static uint32_t timer_enabled(HPETTimer *t)
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return t->config & HPET_TN_ENABLE;
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static uint32_t hpet_time_after(uint64_t a, uint64_t b)
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return ((int32_t)(b) - (int32_t)(a) < 0);
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static uint32_t hpet_time_after64(uint64_t a, uint64_t b)
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return ((int64_t)(b) - (int64_t)(a) < 0);
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static uint64_t ticks_to_ns(uint64_t value)
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return (muldiv64(value, HPET_CLK_PERIOD, FS_PER_NS));
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static uint64_t ns_to_ticks(uint64_t value)
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return (muldiv64(value, FS_PER_NS, HPET_CLK_PERIOD));
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static uint64_t hpet_fixup_reg(uint64_t new, uint64_t old, uint64_t mask)
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static int activating_bit(uint64_t old, uint64_t new, uint64_t mask)
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return (!(old & mask) && (new & mask));
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static int deactivating_bit(uint64_t old, uint64_t new, uint64_t mask)
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return ((old & mask) && !(new & mask));
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static uint64_t hpet_get_ticks(void)
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ticks = ns_to_ticks(qemu_get_clock(vm_clock) + hpet_statep->hpet_offset);
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* calculate diff between comparator value and current ticks
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static inline uint64_t hpet_calculate_diff(HPETTimer *t, uint64_t current)
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if (t->config & HPET_TN_32BIT) {
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cmp = (uint32_t)t->cmp;
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diff = cmp - (uint32_t)current;
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diff = (int32_t)diff > 0 ? diff : (uint32_t)0;
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return (uint64_t)diff;
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diff = cmp - current;
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diff = (int64_t)diff > 0 ? diff : (uint64_t)0;
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static void update_irq(struct HPETTimer *timer)
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if (timer->tn <= 1 && hpet_in_legacy_mode()) {
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/* if LegacyReplacementRoute bit is set, HPET specification requires
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* timer0 be routed to IRQ0 in NON-APIC or IRQ2 in the I/O APIC,
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* timer1 be routed to IRQ8 in NON-APIC or IRQ8 in the I/O APIC.
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if (timer->tn == 0) {
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irq=timer->state->irqs[0];
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irq=timer->state->irqs[8];
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route=timer_int_route(timer);
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irq=timer->state->irqs[route];
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if (timer_enabled(timer) && hpet_enabled()) {
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static void hpet_save(QEMUFile *f, void *opaque)
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HPETState *s = opaque;
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qemu_put_be64s(f, &s->config);
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qemu_put_be64s(f, &s->isr);
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/* save current counter value */
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s->hpet_counter = hpet_get_ticks();
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qemu_put_be64s(f, &s->hpet_counter);
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for (i = 0; i < HPET_NUM_TIMERS; i++) {
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qemu_put_8s(f, &s->timer[i].tn);
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qemu_put_be64s(f, &s->timer[i].config);
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qemu_put_be64s(f, &s->timer[i].cmp);
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qemu_put_be64s(f, &s->timer[i].fsb);
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qemu_put_be64s(f, &s->timer[i].period);
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qemu_put_8s(f, &s->timer[i].wrap_flag);
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if (s->timer[i].qemu_timer) {
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qemu_put_timer(f, s->timer[i].qemu_timer);
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static int hpet_load(QEMUFile *f, void *opaque, int version_id)
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HPETState *s = opaque;
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qemu_get_be64s(f, &s->config);
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qemu_get_be64s(f, &s->isr);
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qemu_get_be64s(f, &s->hpet_counter);
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/* Recalculate the offset between the main counter and guest time */
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s->hpet_offset = ticks_to_ns(s->hpet_counter) - qemu_get_clock(vm_clock);
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for (i = 0; i < HPET_NUM_TIMERS; i++) {
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qemu_get_8s(f, &s->timer[i].tn);
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qemu_get_be64s(f, &s->timer[i].config);
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qemu_get_be64s(f, &s->timer[i].cmp);
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qemu_get_be64s(f, &s->timer[i].fsb);
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qemu_get_be64s(f, &s->timer[i].period);
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qemu_get_8s(f, &s->timer[i].wrap_flag);
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if (s->timer[i].qemu_timer) {
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qemu_get_timer(f, s->timer[i].qemu_timer);
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* timer expiration callback
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static void hpet_timer(void *opaque)
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HPETTimer *t = (HPETTimer*)opaque;
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uint64_t period = t->period;
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uint64_t cur_tick = hpet_get_ticks();
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if (timer_is_periodic(t) && period != 0) {
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if (t->config & HPET_TN_32BIT) {
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while (hpet_time_after(cur_tick, t->cmp))
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t->cmp = (uint32_t)(t->cmp + t->period);
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while (hpet_time_after64(cur_tick, t->cmp))
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diff = hpet_calculate_diff(t, cur_tick);
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qemu_mod_timer(t->qemu_timer, qemu_get_clock(vm_clock)
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+ (int64_t)ticks_to_ns(diff));
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} else if (t->config & HPET_TN_32BIT && !timer_is_periodic(t)) {
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diff = hpet_calculate_diff(t, cur_tick);
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qemu_mod_timer(t->qemu_timer, qemu_get_clock(vm_clock)
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+ (int64_t)ticks_to_ns(diff));
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static void hpet_set_timer(HPETTimer *t)
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uint32_t wrap_diff; /* how many ticks until we wrap? */
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uint64_t cur_tick = hpet_get_ticks();
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/* whenever new timer is being set up, make sure wrap_flag is 0 */
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diff = hpet_calculate_diff(t, cur_tick);
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/* hpet spec says in one-shot 32-bit mode, generate an interrupt when
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* counter wraps in addition to an interrupt with comparator match.
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if (t->config & HPET_TN_32BIT && !timer_is_periodic(t)) {
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wrap_diff = 0xffffffff - (uint32_t)cur_tick;
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if (wrap_diff < (uint32_t)diff) {
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qemu_mod_timer(t->qemu_timer, qemu_get_clock(vm_clock)
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+ (int64_t)ticks_to_ns(diff));
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static void hpet_del_timer(HPETTimer *t)
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qemu_del_timer(t->qemu_timer);
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static uint32_t hpet_ram_readb(void *opaque, target_phys_addr_t addr)
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printf("qemu: hpet_read b at %" PRIx64 "\n", addr);
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static uint32_t hpet_ram_readw(void *opaque, target_phys_addr_t addr)
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printf("qemu: hpet_read w at %" PRIx64 "\n", addr);
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static uint32_t hpet_ram_readl(void *opaque, target_phys_addr_t addr)
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HPETState *s = (HPETState *)opaque;
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uint64_t cur_tick, index;
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dprintf("qemu: Enter hpet_ram_readl at %" PRIx64 "\n", addr);
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/*address range of all TN regs*/
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if (index >= 0x100 && index <= 0x3ff) {
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uint8_t timer_id = (addr - 0x100) / 0x20;
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if (timer_id > HPET_NUM_TIMERS - 1) {
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printf("qemu: timer id out of range\n");
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HPETTimer *timer = &s->timer[timer_id];
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switch ((addr - 0x100) % 0x20) {
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return timer->config;
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case HPET_TN_CFG + 4: // Interrupt capabilities
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return timer->config >> 32;
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case HPET_TN_CMP: // comparator register
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case HPET_TN_CMP + 4:
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return timer->cmp >> 32;
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return timer->fsb >> 32;
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dprintf("qemu: invalid hpet_ram_readl\n");
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return s->capability;
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return s->capability >> 32;
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dprintf("qemu: invalid HPET_CFG + 4 hpet_ram_readl \n");
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cur_tick = hpet_get_ticks();
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cur_tick = s->hpet_counter;
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dprintf("qemu: reading counter = %" PRIx64 "\n", cur_tick);
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case HPET_COUNTER + 4:
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cur_tick = hpet_get_ticks();
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cur_tick = s->hpet_counter;
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dprintf("qemu: reading counter + 4 = %" PRIx64 "\n", cur_tick);
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return cur_tick >> 32;
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dprintf("qemu: invalid hpet_ram_readl\n");
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static void hpet_ram_writeb(void *opaque, target_phys_addr_t addr,
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printf("qemu: invalid hpet_write b at %" PRIx64 " = %#x\n",
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static void hpet_ram_writew(void *opaque, target_phys_addr_t addr,
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printf("qemu: invalid hpet_write w at %" PRIx64 " = %#x\n",
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static void hpet_ram_writel(void *opaque, target_phys_addr_t addr,
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HPETState *s = (HPETState *)opaque;
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uint64_t old_val, new_val, val, index;
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dprintf("qemu: Enter hpet_ram_writel at %" PRIx64 " = %#x\n", addr, value);
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old_val = hpet_ram_readl(opaque, addr);
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/*address range of all TN regs*/
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if (index >= 0x100 && index <= 0x3ff) {
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uint8_t timer_id = (addr - 0x100) / 0x20;
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dprintf("qemu: hpet_ram_writel timer_id = %#x \n", timer_id);
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HPETTimer *timer = &s->timer[timer_id];
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switch ((addr - 0x100) % 0x20) {
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dprintf("qemu: hpet_ram_writel HPET_TN_CFG\n");
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val = hpet_fixup_reg(new_val, old_val, HPET_TN_CFG_WRITE_MASK);
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timer->config = (timer->config & 0xffffffff00000000ULL) | val;
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if (new_val & HPET_TN_32BIT) {
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timer->cmp = (uint32_t)timer->cmp;
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timer->period = (uint32_t)timer->period;
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if (new_val & HPET_TIMER_TYPE_LEVEL) {
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printf("qemu: level-triggered hpet not supported\n");
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case HPET_TN_CFG + 4: // Interrupt capabilities
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dprintf("qemu: invalid HPET_TN_CFG+4 write\n");
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case HPET_TN_CMP: // comparator register
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dprintf("qemu: hpet_ram_writel HPET_TN_CMP \n");
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if (timer->config & HPET_TN_32BIT)
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new_val = (uint32_t)new_val;
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if (!timer_is_periodic(timer) ||
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(timer->config & HPET_TN_SETVAL))
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timer->cmp = (timer->cmp & 0xffffffff00000000ULL)
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if (timer_is_periodic(timer)) {
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* FIXME: Clamp period to reasonable min value?
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* Clamp period to reasonable max value
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new_val &= (timer->config & HPET_TN_32BIT ? ~0u : ~0ull) >> 1;
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timer->period = (timer->period & 0xffffffff00000000ULL)
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timer->config &= ~HPET_TN_SETVAL;
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hpet_set_timer(timer);
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case HPET_TN_CMP + 4: // comparator register high order
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dprintf("qemu: hpet_ram_writel HPET_TN_CMP + 4\n");
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if (!timer_is_periodic(timer) ||
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(timer->config & HPET_TN_SETVAL))
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timer->cmp = (timer->cmp & 0xffffffffULL)
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* FIXME: Clamp period to reasonable min value?
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* Clamp period to reasonable max value
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new_val &= (timer->config
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& HPET_TN_32BIT ? ~0u : ~0ull) >> 1;
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timer->period = (timer->period & 0xffffffffULL)
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timer->config &= ~HPET_TN_SETVAL;
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hpet_set_timer(timer);
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case HPET_TN_ROUTE + 4:
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dprintf("qemu: hpet_ram_writel HPET_TN_ROUTE + 4\n");
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dprintf("qemu: invalid hpet_ram_writel\n");
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val = hpet_fixup_reg(new_val, old_val, HPET_CFG_WRITE_MASK);
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s->config = (s->config & 0xffffffff00000000ULL) | val;
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if (activating_bit(old_val, new_val, HPET_CFG_ENABLE)) {
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/* Enable main counter and interrupt generation. */
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s->hpet_offset = ticks_to_ns(s->hpet_counter)
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- qemu_get_clock(vm_clock);
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for (i = 0; i < HPET_NUM_TIMERS; i++)
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if ((&s->timer[i])->cmp != ~0ULL)
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hpet_set_timer(&s->timer[i]);
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else if (deactivating_bit(old_val, new_val, HPET_CFG_ENABLE)) {
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/* Halt main counter and disable interrupt generation. */
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s->hpet_counter = hpet_get_ticks();
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for (i = 0; i < HPET_NUM_TIMERS; i++)
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hpet_del_timer(&s->timer[i]);
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/* i8254 and RTC are disabled when HPET is in legacy mode */
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if (activating_bit(old_val, new_val, HPET_CFG_LEGACY)) {
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} else if (deactivating_bit(old_val, new_val, HPET_CFG_LEGACY)) {
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dprintf("qemu: invalid HPET_CFG+4 write \n");
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/* FIXME: need to handle level-triggered interrupts */
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printf("qemu: Writing counter while HPET enabled!\n");
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s->hpet_counter = (s->hpet_counter & 0xffffffff00000000ULL)
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dprintf("qemu: HPET counter written. ctr = %#x -> %" PRIx64 "\n",
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value, s->hpet_counter);
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case HPET_COUNTER + 4:
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printf("qemu: Writing counter while HPET enabled!\n");
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s->hpet_counter = (s->hpet_counter & 0xffffffffULL)
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| (((uint64_t)value) << 32);
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dprintf("qemu: HPET counter + 4 written. ctr = %#x -> %" PRIx64 "\n",
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value, s->hpet_counter);
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dprintf("qemu: invalid hpet_ram_writel\n");
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static CPUReadMemoryFunc * const hpet_ram_read[] = {
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static CPUWriteMemoryFunc * const hpet_ram_write[] = {
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static void hpet_reset(void *opaque) {
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HPETState *s = opaque;
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static int count = 0;
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for (i=0; i<HPET_NUM_TIMERS; i++) {
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HPETTimer *timer = &s->timer[i];
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hpet_del_timer(timer);
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timer->config = HPET_TN_PERIODIC_CAP | HPET_TN_SIZE_CAP;
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/* advertise availability of ioapic inti2 */
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timer->config |= 0x00000004ULL << 32;
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timer->period = 0ULL;
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timer->wrap_flag = 0;
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s->hpet_counter = 0ULL;
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s->hpet_offset = 0ULL;
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/* 64-bit main counter; 3 timers supported; LegacyReplacementRoute. */
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s->capability = 0x8086a201ULL;
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s->capability |= ((HPET_CLK_PERIOD) << 32);
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/* we don't enable pit when hpet_reset is first called (by hpet_init)
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* because hpet is taking over for pit here. On subsequent invocations,
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* hpet_reset is called due to system reset. At this point control must
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* be returned to pit until SW reenables hpet.
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void hpet_init(qemu_irq *irq) {
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dprintf ("hpet_init\n");
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s = qemu_mallocz(sizeof(HPETState));
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for (i=0; i<HPET_NUM_TIMERS; i++) {
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HPETTimer *timer = &s->timer[i];
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timer->qemu_timer = qemu_new_timer(vm_clock, hpet_timer, timer);
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register_savevm("hpet", -1, 1, hpet_save, hpet_load, s);
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qemu_register_reset(hpet_reset, s);
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iomemtype = cpu_register_io_memory(hpet_ram_read,
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cpu_register_physical_memory(HPET_BASE, 0x400, iomemtype);