+/*
+ * HPET address is set in acpi/boot.c, when an ACPI entry exists
+ */
+unsigned long hpet_address;
+static void __iomem * hpet_virt_address;
+
+static inline unsigned long hpet_readl(unsigned long a)
+{
+ return readl(hpet_virt_address + a);
+}
+
+static inline void hpet_writel(unsigned long d, unsigned long a)
+{
+ writel(d, hpet_virt_address + a);
+}
+
+/*
+ * HPET command line enable / disable
+ */
+static int boot_hpet_disable;
+
+static int __init hpet_setup(char* str)
+{
+ if (str) {
+ if (!strncmp("disable", str, 7))
+ boot_hpet_disable = 1;
+ }
+ return 1;
+}
+__setup("hpet=", hpet_setup);
+
+static inline int is_hpet_capable(void)
+{
+ return (!boot_hpet_disable && hpet_address);
+}
+
+/*
+ * HPET timer interrupt enable / disable
+ */
+static int hpet_legacy_int_enabled;
+
+/**
+ * is_hpet_enabled - check whether the hpet timer interrupt is enabled
+ */
+int is_hpet_enabled(void)
+{
+ return is_hpet_capable() && hpet_legacy_int_enabled;
+}
+
+/*
+ * When the hpet driver (/dev/hpet) is enabled, we need to reserve
+ * timer 0 and timer 1 in case of RTC emulation.
+ */
+#ifdef CONFIG_HPET
+static void hpet_reserve_platform_timers(unsigned long id)
+{
+ struct hpet __iomem *hpet = hpet_virt_address;
+ struct hpet_timer __iomem *timer = &hpet->hpet_timers[2];
+ unsigned int nrtimers, i;
+ struct hpet_data hd;
+
+ nrtimers = ((id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT) + 1;
+
+ memset(&hd, 0, sizeof (hd));
+ hd.hd_phys_address = hpet_address;
+ hd.hd_address = hpet_virt_address;
+ hd.hd_nirqs = nrtimers;
+ hd.hd_flags = HPET_DATA_PLATFORM;
+ hpet_reserve_timer(&hd, 0);
+
+#ifdef CONFIG_HPET_EMULATE_RTC
+ hpet_reserve_timer(&hd, 1);
+#endif
+
+ hd.hd_irq[0] = HPET_LEGACY_8254;
+ hd.hd_irq[1] = HPET_LEGACY_RTC;
+
+ for (i = 2; i < nrtimers; timer++, i++)
+ hd.hd_irq[i] = (timer->hpet_config & Tn_INT_ROUTE_CNF_MASK) >>
+ Tn_INT_ROUTE_CNF_SHIFT;
+
+ hpet_alloc(&hd);
+
+}
+#else
+static void hpet_reserve_platform_timers(unsigned long id) { }
+#endif
+
+/*
+ * Common hpet info
+ */
+static unsigned long hpet_period;
+
+static void hpet_set_mode(enum clock_event_mode mode,
+ struct clock_event_device *evt);
+static int hpet_next_event(unsigned long delta,
+ struct clock_event_device *evt);
+
+/*
+ * The hpet clock event device
+ */
+static struct clock_event_device hpet_clockevent = {
+ .name = "hpet",
+ .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+ .set_mode = hpet_set_mode,
+ .set_next_event = hpet_next_event,
+ .shift = 32,
+ .irq = 0,
+};
+
+static void hpet_start_counter(void)
+{
+ unsigned long cfg = hpet_readl(HPET_CFG);
+
+ cfg &= ~HPET_CFG_ENABLE;
+ hpet_writel(cfg, HPET_CFG);
+ hpet_writel(0, HPET_COUNTER);
+ hpet_writel(0, HPET_COUNTER + 4);
+ cfg |= HPET_CFG_ENABLE;
+ hpet_writel(cfg, HPET_CFG);
+}
+
+static void hpet_enable_int(void)
+{
+ unsigned long cfg = hpet_readl(HPET_CFG);
+
+ cfg |= HPET_CFG_LEGACY;
+ hpet_writel(cfg, HPET_CFG);
+ hpet_legacy_int_enabled = 1;
+}
+
+static void hpet_set_mode(enum clock_event_mode mode,
+ struct clock_event_device *evt)
+{
+ unsigned long cfg, cmp, now;
+ uint64_t delta;
+
+ switch(mode) {
+ case CLOCK_EVT_MODE_PERIODIC:
+ delta = ((uint64_t)(NSEC_PER_SEC/HZ)) * hpet_clockevent.mult;
+ delta >>= hpet_clockevent.shift;
+ now = hpet_readl(HPET_COUNTER);
+ cmp = now + (unsigned long) delta;
+ cfg = hpet_readl(HPET_T0_CFG);
+ cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC |
+ HPET_TN_SETVAL | HPET_TN_32BIT;
+ hpet_writel(cfg, HPET_T0_CFG);
+ /*
+ * The first write after writing TN_SETVAL to the
+ * config register sets the counter value, the second
+ * write sets the period.
+ */
+ hpet_writel(cmp, HPET_T0_CMP);
+ udelay(1);
+ hpet_writel((unsigned long) delta, HPET_T0_CMP);
+ break;
+
+ case CLOCK_EVT_MODE_ONESHOT:
+ cfg = hpet_readl(HPET_T0_CFG);
+ cfg &= ~HPET_TN_PERIODIC;
+ cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
+ hpet_writel(cfg, HPET_T0_CFG);
+ break;
+
+ case CLOCK_EVT_MODE_UNUSED:
+ case CLOCK_EVT_MODE_SHUTDOWN:
+ cfg = hpet_readl(HPET_T0_CFG);
+ cfg &= ~HPET_TN_ENABLE;
+ hpet_writel(cfg, HPET_T0_CFG);
+ break;
+ }
+}
+
+static int hpet_next_event(unsigned long delta,
+ struct clock_event_device *evt)
+{
+ unsigned long cnt;
+
+ cnt = hpet_readl(HPET_COUNTER);
+ cnt += delta;
+ hpet_writel(cnt, HPET_T0_CMP);
+
+ return ((long)(hpet_readl(HPET_COUNTER) - cnt ) > 0);
+}
+
+/*
+ * Try to setup the HPET timer
+ */
+int __init hpet_enable(void)
+{
+ unsigned long id;
+ uint64_t hpet_freq;
+
+ if (!is_hpet_capable())
+ return 0;
+
+ hpet_virt_address = ioremap_nocache(hpet_address, HPET_MMAP_SIZE);
+
+ /*
+ * Read the period and check for a sane value:
+ */
+ hpet_period = hpet_readl(HPET_PERIOD);
+ if (hpet_period < HPET_MIN_PERIOD || hpet_period > HPET_MAX_PERIOD)
+ goto out_nohpet;
+
+ /*
+ * The period is a femto seconds value. We need to calculate the
+ * scaled math multiplication factor for nanosecond to hpet tick
+ * conversion.
+ */
+ hpet_freq = 1000000000000000ULL;
+ do_div(hpet_freq, hpet_period);
+ hpet_clockevent.mult = div_sc((unsigned long) hpet_freq,
+ NSEC_PER_SEC, 32);
+ /* Calculate the min / max delta */
+ hpet_clockevent.max_delta_ns = clockevent_delta2ns(0x7FFFFFFF,
+ &hpet_clockevent);
+ hpet_clockevent.min_delta_ns = clockevent_delta2ns(0x30,
+ &hpet_clockevent);
+
+ /*
+ * Read the HPET ID register to retrieve the IRQ routing
+ * information and the number of channels
+ */
+ id = hpet_readl(HPET_ID);
+
+#ifdef CONFIG_HPET_EMULATE_RTC
+ /*
+ * The legacy routing mode needs at least two channels, tick timer
+ * and the rtc emulation channel.
+ */
+ if (!(id & HPET_ID_NUMBER))
+ goto out_nohpet;
+#endif
+
+ /* Start the counter */
+ hpet_start_counter();
+
+ if (id & HPET_ID_LEGSUP) {
+ hpet_enable_int();
+ hpet_reserve_platform_timers(id);
+ /*
+ * Start hpet with the boot cpu mask and make it
+ * global after the IO_APIC has been initialized.
+ */
+ hpet_clockevent.cpumask =cpumask_of_cpu(0);
+ clockevents_register_device(&hpet_clockevent);
+ global_clock_event = &hpet_clockevent;
+ return 1;
+ }
+ return 0;