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hpet.c

#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/hpet.h>
#include <linux/init.h>
#include <linux/sysdev.h>
#include <linux/pm.h>
#include <linux/delay.h>

#include <asm/fixmap.h>
#include <asm/hpet.h>
#include <asm/i8253.h>
#include <asm/io.h>

#define HPET_MASK CLOCKSOURCE_MASK(32)
#define HPET_SHIFT      22

/* FSEC = 10^-15 NSEC = 10^-9 */
#define FSEC_PER_NSEC   1000000

/*
 * HPET address is set in acpi/boot.c, when an ACPI entry exists
 */
unsigned long hpet_address;
static void __iomem *hpet_virt_address;

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);
}

#ifdef CONFIG_X86_64

#include <asm/pgtable.h>

static inline void hpet_set_mapping(void)
{
      set_fixmap_nocache(FIX_HPET_BASE, hpet_address);
      __set_fixmap(VSYSCALL_HPET, hpet_address, PAGE_KERNEL_VSYSCALL_NOCACHE);
      hpet_virt_address = (void __iomem *)fix_to_virt(FIX_HPET_BASE);
}

static inline void hpet_clear_mapping(void)
{
      hpet_virt_address = NULL;
}

#else

static inline void hpet_set_mapping(void)
{
      hpet_virt_address = ioremap_nocache(hpet_address, HPET_MMAP_SIZE);
}

static inline void hpet_clear_mapping(void)
{
      iounmap(hpet_virt_address);
      hpet_virt_address = NULL;
}
#endif

/*
 * HPET command line enable / disable
 */
static int boot_hpet_disable;
int hpet_force_user;

static int __init hpet_setup(char* str)
{
      if (str) {
            if (!strncmp("disable", str, 7))
                  boot_hpet_disable = 1;
            if (!strncmp("force", str, 5))
                  hpet_force_user = 1;
      }
      return 1;
}
__setup("hpet=", hpet_setup);

static int __init disable_hpet(char *str)
{
      boot_hpet_disable = 1;
      return 1;
}
__setup("nohpet", disable_hpet);

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;
      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_legacy_set_mode(enum clock_event_mode mode,
                    struct clock_event_device *evt);
static int hpet_legacy_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_legacy_set_mode,
      .set_next_event = hpet_legacy_next_event,
      .shift            = 32,
      .irq        = 0,
      .rating           = 50,
};

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_resume_device(void)
{
      force_hpet_resume();
}

static void hpet_restart_counter(void)
{
      hpet_resume_device();
      hpet_start_counter();
}

static void hpet_enable_legacy_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_legacy_clockevent_register(void)
{
      uint64_t hpet_freq;

      /* Start HPET legacy interrupts */
      hpet_enable_legacy_int();

      /*
       * 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);

      /*
       * Start hpet with the boot cpu mask and make it
       * global after the IO_APIC has been initialized.
       */
      hpet_clockevent.cpumask = cpumask_of_cpu(smp_processor_id());
      clockevents_register_device(&hpet_clockevent);
      global_clock_event = &hpet_clockevent;
      printk(KERN_DEBUG "hpet clockevent registered\n");
}

static void hpet_legacy_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;

      case CLOCK_EVT_MODE_RESUME:
            hpet_enable_legacy_int();
            break;
      }
}

static int hpet_legacy_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) ? -ETIME : 0;
}

/*
 * Clock source related code
 */
static cycle_t read_hpet(void)
{
      return (cycle_t)hpet_readl(HPET_COUNTER);
}

#ifdef CONFIG_X86_64
static cycle_t __vsyscall_fn vread_hpet(void)
{
      return readl((const void __iomem *)fix_to_virt(VSYSCALL_HPET) + 0xf0);
}
#endif

static struct clocksource clocksource_hpet = {
      .name       = "hpet",
      .rating           = 250,
      .read       = read_hpet,
      .mask       = HPET_MASK,
      .shift            = HPET_SHIFT,
      .flags            = CLOCK_SOURCE_IS_CONTINUOUS,
      .resume           = hpet_restart_counter,
#ifdef CONFIG_X86_64
      .vread            = vread_hpet,
#endif
};

static int hpet_clocksource_register(void)
{
      u64 tmp, start, now;
      cycle_t t1;

      /* Start the counter */
      hpet_start_counter();

      /* Verify whether hpet counter works */
      t1 = read_hpet();
      rdtscll(start);

      /*
       * We don't know the TSC frequency yet, but waiting for
       * 200000 TSC cycles is safe:
       * 4 GHz == 50us
       * 1 GHz == 200us
       */
      do {
            rep_nop();
            rdtscll(now);
      } while ((now - start) < 200000UL);

      if (t1 == read_hpet()) {
            printk(KERN_WARNING
                   "HPET counter not counting. HPET disabled\n");
            return -ENODEV;
      }

      /* Initialize and register HPET clocksource
       *
       * hpet period is in femto seconds per cycle
       * so we need to convert this to ns/cyc units
       * approximated by mult/2^shift
       *
       *  fsec/cyc * 1nsec/1000000fsec = nsec/cyc = mult/2^shift
       *  fsec/cyc * 1ns/1000000fsec * 2^shift = mult
       *  fsec/cyc * 2^shift * 1nsec/1000000fsec = mult
       *  (fsec/cyc << shift)/1000000 = mult
       *  (hpet_period << shift)/FSEC_PER_NSEC = mult
       */
      tmp = (u64)hpet_period << HPET_SHIFT;
      do_div(tmp, FSEC_PER_NSEC);
      clocksource_hpet.mult = (u32)tmp;

      clocksource_register(&clocksource_hpet);

      return 0;
}

/*
 * Try to setup the HPET timer
 */
int __init hpet_enable(void)
{
      unsigned long id;

      if (!is_hpet_capable())
            return 0;

      hpet_set_mapping();

      /*
       * 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;

      /*
       * 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

      if (hpet_clocksource_register())
            goto out_nohpet;

      if (id & HPET_ID_LEGSUP) {
            hpet_legacy_clockevent_register();
            return 1;
      }
      return 0;

out_nohpet:
      hpet_clear_mapping();
      boot_hpet_disable = 1;
      return 0;
}

/*
 * Needs to be late, as the reserve_timer code calls kalloc !
 *
 * Not a problem on i386 as hpet_enable is called from late_time_init,
 * but on x86_64 it is necessary !
 */
static __init int hpet_late_init(void)
{
      if (boot_hpet_disable)
            return -ENODEV;

      if (!hpet_address) {
            if (!force_hpet_address)
                  return -ENODEV;

            hpet_address = force_hpet_address;
            hpet_enable();
            if (!hpet_virt_address)
                  return -ENODEV;
      }

      hpet_reserve_platform_timers(hpet_readl(HPET_ID));

      return 0;
}
fs_initcall(hpet_late_init);

void hpet_disable(void)
{
      if (is_hpet_capable()) {
            unsigned long cfg = hpet_readl(HPET_CFG);

            if (hpet_legacy_int_enabled) {
                  cfg &= ~HPET_CFG_LEGACY;
                  hpet_legacy_int_enabled = 0;
            }
            cfg &= ~HPET_CFG_ENABLE;
            hpet_writel(cfg, HPET_CFG);
      }
}

#ifdef CONFIG_HPET_EMULATE_RTC

/* HPET in LegacyReplacement Mode eats up RTC interrupt line. When, HPET
 * is enabled, we support RTC interrupt functionality in software.
 * RTC has 3 kinds of interrupts:
 * 1) Update Interrupt - generate an interrupt, every sec, when RTC clock
 *    is updated
 * 2) Alarm Interrupt - generate an interrupt at a specific time of day
 * 3) Periodic Interrupt - generate periodic interrupt, with frequencies
 *    2Hz-8192Hz (2Hz-64Hz for non-root user) (all freqs in powers of 2)
 * (1) and (2) above are implemented using polling at a frequency of
 * 64 Hz. The exact frequency is a tradeoff between accuracy and interrupt
 * overhead. (DEFAULT_RTC_INT_FREQ)
 * For (3), we use interrupts at 64Hz or user specified periodic
 * frequency, whichever is higher.
 */
#include <linux/mc146818rtc.h>
#include <linux/rtc.h>

#define DEFAULT_RTC_INT_FREQ  64
#define DEFAULT_RTC_SHIFT     6
#define RTC_NUM_INTS          1

static unsigned long hpet_rtc_flags;
static unsigned long hpet_prev_update_sec;
static struct rtc_time hpet_alarm_time;
static unsigned long hpet_pie_count;
static unsigned long hpet_t1_cmp;
static unsigned long hpet_default_delta;
static unsigned long hpet_pie_delta;
static unsigned long hpet_pie_limit;

/*
 * Timer 1 for RTC emulation. We use one shot mode, as periodic mode
 * is not supported by all HPET implementations for timer 1.
 *
 * hpet_rtc_timer_init() is called when the rtc is initialized.
 */
int hpet_rtc_timer_init(void)
{
      unsigned long cfg, cnt, delta, flags;

      if (!is_hpet_enabled())
            return 0;

      if (!hpet_default_delta) {
            uint64_t clc;

            clc = (uint64_t) hpet_clockevent.mult * NSEC_PER_SEC;
            clc >>= hpet_clockevent.shift + DEFAULT_RTC_SHIFT;
            hpet_default_delta = (unsigned long) clc;
      }

      if (!(hpet_rtc_flags & RTC_PIE) || hpet_pie_limit)
            delta = hpet_default_delta;
      else
            delta = hpet_pie_delta;

      local_irq_save(flags);

      cnt = delta + hpet_readl(HPET_COUNTER);
      hpet_writel(cnt, HPET_T1_CMP);
      hpet_t1_cmp = cnt;

      cfg = hpet_readl(HPET_T1_CFG);
      cfg &= ~HPET_TN_PERIODIC;
      cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
      hpet_writel(cfg, HPET_T1_CFG);

      local_irq_restore(flags);

      return 1;
}

/*
 * The functions below are called from rtc driver.
 * Return 0 if HPET is not being used.
 * Otherwise do the necessary changes and return 1.
 */
int hpet_mask_rtc_irq_bit(unsigned long bit_mask)
{
      if (!is_hpet_enabled())
            return 0;

      hpet_rtc_flags &= ~bit_mask;
      return 1;
}

int hpet_set_rtc_irq_bit(unsigned long bit_mask)
{
      unsigned long oldbits = hpet_rtc_flags;

      if (!is_hpet_enabled())
            return 0;

      hpet_rtc_flags |= bit_mask;

      if (!oldbits)
            hpet_rtc_timer_init();

      return 1;
}

int hpet_set_alarm_time(unsigned char hrs, unsigned char min,
                  unsigned char sec)
{
      if (!is_hpet_enabled())
            return 0;

      hpet_alarm_time.tm_hour = hrs;
      hpet_alarm_time.tm_min = min;
      hpet_alarm_time.tm_sec = sec;

      return 1;
}

int hpet_set_periodic_freq(unsigned long freq)
{
      uint64_t clc;

      if (!is_hpet_enabled())
            return 0;

      if (freq <= DEFAULT_RTC_INT_FREQ)
            hpet_pie_limit = DEFAULT_RTC_INT_FREQ / freq;
      else {
            clc = (uint64_t) hpet_clockevent.mult * NSEC_PER_SEC;
            do_div(clc, freq);
            clc >>= hpet_clockevent.shift;
            hpet_pie_delta = (unsigned long) clc;
      }
      return 1;
}

int hpet_rtc_dropped_irq(void)
{
      return is_hpet_enabled();
}

static void hpet_rtc_timer_reinit(void)
{
      unsigned long cfg, delta;
      int lost_ints = -1;

      if (unlikely(!hpet_rtc_flags)) {
            cfg = hpet_readl(HPET_T1_CFG);
            cfg &= ~HPET_TN_ENABLE;
            hpet_writel(cfg, HPET_T1_CFG);
            return;
      }

      if (!(hpet_rtc_flags & RTC_PIE) || hpet_pie_limit)
            delta = hpet_default_delta;
      else
            delta = hpet_pie_delta;

      /*
       * Increment the comparator value until we are ahead of the
       * current count.
       */
      do {
            hpet_t1_cmp += delta;
            hpet_writel(hpet_t1_cmp, HPET_T1_CMP);
            lost_ints++;
      } while ((long)(hpet_readl(HPET_COUNTER) - hpet_t1_cmp) > 0);

      if (lost_ints) {
            if (hpet_rtc_flags & RTC_PIE)
                  hpet_pie_count += lost_ints;
            if (printk_ratelimit())
                  printk(KERN_WARNING "rtc: lost %d interrupts\n",
                        lost_ints);
      }
}

irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id)
{
      struct rtc_time curr_time;
      unsigned long rtc_int_flag = 0;

      hpet_rtc_timer_reinit();

      if (hpet_rtc_flags & (RTC_UIE | RTC_AIE))
            rtc_get_rtc_time(&curr_time);

      if (hpet_rtc_flags & RTC_UIE &&
          curr_time.tm_sec != hpet_prev_update_sec) {
            rtc_int_flag = RTC_UF;
            hpet_prev_update_sec = curr_time.tm_sec;
      }

      if (hpet_rtc_flags & RTC_PIE &&
          ++hpet_pie_count >= hpet_pie_limit) {
            rtc_int_flag |= RTC_PF;
            hpet_pie_count = 0;
      }

      if (hpet_rtc_flags & RTC_AIE &&
          (curr_time.tm_sec == hpet_alarm_time.tm_sec) &&
          (curr_time.tm_min == hpet_alarm_time.tm_min) &&
          (curr_time.tm_hour == hpet_alarm_time.tm_hour))
                  rtc_int_flag |= RTC_AF;

      if (rtc_int_flag) {
            rtc_int_flag |= (RTC_IRQF | (RTC_NUM_INTS << 8));
            rtc_interrupt(rtc_int_flag, dev_id);
      }
      return IRQ_HANDLED;
}
#endif

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