hpet.c

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/*
 * Intel & MS High Precision Event Timer Implementation.
 *
 * Copyright (C) 2003 Intel Corporation
 *  Venki Pallipadi
 * (c) Copyright 2004 Hewlett-Packard Development Company, L.P.
 *  Bob Picco <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/major.h>
#include <linux/ioport.h>
#include <linux/fcntl.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/spinlock.h>
#include <linux/sysctl.h>
#include <linux/wait.h>
#include <linux/bcd.h>
#include <linux/seq_file.h>
#include <linux/bitops.h>
#include <linux/compat.h>
#include <linux/clocksource.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/io.h>

#include <asm/current.h>
#include <asm/irq.h>
#include <asm/div64.h>

#include <linux/acpi.h>
#include <acpi/acpi_bus.h>
#include <linux/hpet.h>

/*
 * The High Precision Event Timer driver.
 * This driver is closely modelled after the rtc.c driver.
 * http://www.intel.com/hardwaredesign/hpetspec_1.pdf
 */
#define HPET_USER_FREQ  (64)
#define HPET_DRIFT  (500)

#define HPET_RANGE_SIZE     1024    /* from HPET spec */


/* WARNING -- don't get confused.  These macros are never used
 * to write the (single) counter, and rarely to read it.
 * They're badly named; to fix, someday.
 */
#if BITS_PER_LONG == 64
#define write_counter(V, MC)    writeq(V, MC)
#define read_counter(MC)    readq(MC)
#else
#define write_counter(V, MC)    writel(V, MC)
#define read_counter(MC)    readl(MC)
#endif

static DEFINE_MUTEX(hpet_mutex); /* replaces BKL */
static u32 hpet_nhpet, hpet_max_freq = HPET_USER_FREQ;

/* This clocksource driver currently only works on ia64 */
#ifdef CONFIG_IA64
static void __iomem *hpet_mctr;

static cycle_t read_hpet(struct clocksource *cs)
{
    return (cycle_t)read_counter((void __iomem *)hpet_mctr);
}

static struct clocksource clocksource_hpet = {
    .name       = "hpet",
    .rating     = 250,
    .read       = read_hpet,
    .mask       = CLOCKSOURCE_MASK(64),
    .flags      = CLOCK_SOURCE_IS_CONTINUOUS,
};
static struct clocksource *hpet_clocksource;
#endif

/* A lock for concurrent access by app and isr hpet activity. */
static DEFINE_SPINLOCK(hpet_lock);

#define HPET_DEV_NAME   (7)

struct hpet_dev {
    struct hpets *hd_hpets;
    struct hpet __iomem *hd_hpet;
    struct hpet_timer __iomem *hd_timer;
    unsigned long hd_ireqfreq;
    unsigned long hd_irqdata;
    wait_queue_head_t hd_waitqueue;
    struct fasync_struct *hd_async_queue;
    unsigned int hd_flags;
    unsigned int hd_irq;
    unsigned int hd_hdwirq;
    char hd_name[HPET_DEV_NAME];
};

struct hpets {
    struct hpets *hp_next;
    struct hpet __iomem *hp_hpet;
    unsigned long hp_hpet_phys;
    struct clocksource *hp_clocksource;
    unsigned long long hp_tick_freq;
    unsigned long hp_delta;
    unsigned int hp_ntimer;
    unsigned int hp_which;
    struct hpet_dev hp_dev[1];
};

static struct hpets *hpets;

#define HPET_OPEN       0x0001
#define HPET_IE         0x0002  /* interrupt enabled */
#define HPET_PERIODIC       0x0004
#define HPET_SHARED_IRQ     0x0008


#ifndef readq
static inline unsigned long long readq(void __iomem *addr)
{
    return readl(addr) | (((unsigned long long)readl(addr + 4)) << 32LL);
}
#endif

#ifndef writeq
static inline void writeq(unsigned long long v, void __iomem *addr)
{
    writel(v & 0xffffffff, addr);
    writel(v >> 32, addr + 4);
}
#endif

static irqreturn_t hpet_interrupt(int irq, void *data)
{
    struct hpet_dev *devp;
    unsigned long isr;

    devp = data;
    isr = 1 << (devp - devp->hd_hpets->hp_dev);

    if ((devp->hd_flags & HPET_SHARED_IRQ) &&
        !(isr & readl(&devp->hd_hpet->hpet_isr)))
        return IRQ_NONE;

    spin_lock(&hpet_lock);
    devp->hd_irqdata++;

    /*
     * For non-periodic timers, increment the accumulator.
     * This has the effect of treating non-periodic like periodic.
     */
    if ((devp->hd_flags & (HPET_IE | HPET_PERIODIC)) == HPET_IE) {
        unsigned long m, t, mc, base, k;
        struct hpet __iomem *hpet = devp->hd_hpet;
        struct hpets *hpetp = devp->hd_hpets;

        t = devp->hd_ireqfreq;
        m = read_counter(&devp->hd_timer->hpet_compare);
        mc = read_counter(&hpet->hpet_mc);
        /* The time for the next interrupt would logically be t + m,
         * however, if we are very unlucky and the interrupt is delayed
         * for longer than t then we will completely miss the next
         * interrupt if we set t + m and an application will hang.
         * Therefore we need to make a more complex computation assuming
         * that there exists a k for which the following is true:
         * k * t + base < mc + delta
         * (k + 1) * t + base > mc + delta
         * where t is the interval in hpet ticks for the given freq,
         * base is the theoretical start value 0 < base < t,
         * mc is the main counter value at the time of the interrupt,
         * delta is the time it takes to write the a value to the
         * comparator.
         * k may then be computed as (mc - base + delta) / t .
         */
        base = mc % t;
        k = (mc - base + hpetp->hp_delta) / t;
        write_counter(t * (k + 1) + base,
                  &devp->hd_timer->hpet_compare);
    }

    if (devp->hd_flags & HPET_SHARED_IRQ)
        writel(isr, &devp->hd_hpet->hpet_isr);
    spin_unlock(&hpet_lock);

    wake_up_interruptible(&devp->hd_waitqueue);

    kill_fasync(&devp->hd_async_queue, SIGIO, POLL_IN);

    return IRQ_HANDLED;
}

static void hpet_timer_set_irq(struct hpet_dev *devp)
{
    unsigned long v;
    int irq, gsi;
    struct hpet_timer __iomem *timer;

    spin_lock_irq(&hpet_lock);
    if (devp->hd_hdwirq) {
        spin_unlock_irq(&hpet_lock);
        return;
    }

    timer = devp->hd_timer;

    /* we prefer level triggered mode */
    v = readl(&timer->hpet_config);
    if (!(v & Tn_INT_TYPE_CNF_MASK)) {
        v |= Tn_INT_TYPE_CNF_MASK;
        writel(v, &timer->hpet_config);
    }
    spin_unlock_irq(&hpet_lock);

    v = (readq(&timer->hpet_config) & Tn_INT_ROUTE_CAP_MASK) >>
                 Tn_INT_ROUTE_CAP_SHIFT;

    /*
     * In PIC mode, skip IRQ0-4, IRQ6-9, IRQ12-15 which is always used by
     * legacy device. In IO APIC mode, we skip all the legacy IRQS.
     */
    if (acpi_irq_model == ACPI_IRQ_MODEL_PIC)
        v &= ~0xf3df;
    else
        v &= ~0xffff;

    for_each_set_bit(irq, &v, HPET_MAX_IRQ) {
        if (irq >= nr_irqs) {
            irq = HPET_MAX_IRQ;
            break;
        }

        gsi = acpi_register_gsi(NULL, irq, ACPI_LEVEL_SENSITIVE,
                    ACPI_ACTIVE_LOW);
        if (gsi > 0)
            break;

        /* FIXME: Setup interrupt source table */
    }

    if (irq < HPET_MAX_IRQ) {
        spin_lock_irq(&hpet_lock);
        v = readl(&timer->hpet_config);
        v |= irq << Tn_INT_ROUTE_CNF_SHIFT;
        writel(v, &timer->hpet_config);
        devp->hd_hdwirq = gsi;
        spin_unlock_irq(&hpet_lock);
    }
    return;
}

static int hpet_open(struct inode *inode, struct file *file)
{
    struct hpet_dev *devp;
    struct hpets *hpetp;
    int i;

    if (file->f_mode & FMODE_WRITE)
        return -EINVAL;

    mutex_lock(&hpet_mutex);
    spin_lock_irq(&hpet_lock);

    for (devp = NULL, hpetp = hpets; hpetp && !devp; hpetp = hpetp->hp_next)
        for (i = 0; i < hpetp->hp_ntimer; i++)
            if (hpetp->hp_dev[i].hd_flags & HPET_OPEN)
                continue;
            else {
                devp = &hpetp->hp_dev[i];
                break;
            }

    if (!devp) {
        spin_unlock_irq(&hpet_lock);
        mutex_unlock(&hpet_mutex);
        return -EBUSY;
    }

    file->private_data = devp;
    devp->hd_irqdata = 0;
    devp->hd_flags |= HPET_OPEN;
    spin_unlock_irq(&hpet_lock);
    mutex_unlock(&hpet_mutex);

    hpet_timer_set_irq(devp);

    return 0;
}

static ssize_t
hpet_read(struct file *file, char __user *buf, size_t count, loff_t * ppos)
{
    DECLARE_WAITQUEUE(wait, current);
    unsigned long data;
    ssize_t retval;
    struct hpet_dev *devp;

    devp = file->private_data;
    if (!devp->hd_ireqfreq)
        return -EIO;

    if (count < sizeof(unsigned long))
        return -EINVAL;

    add_wait_queue(&devp->hd_waitqueue, &wait);

    for ( ; ; ) {
        set_current_state(TASK_INTERRUPTIBLE);

        spin_lock_irq(&hpet_lock);
        data = devp->hd_irqdata;
        devp->hd_irqdata = 0;
        spin_unlock_irq(&hpet_lock);

        if (data)
            break;
        else if (file->f_flags & O_NONBLOCK) {
            retval = -EAGAIN;
            goto out;
        } else if (signal_pending(current)) {
            retval = -ERESTARTSYS;
            goto out;
        }
        schedule();
    }

    retval = put_user(data, (unsigned long __user *)buf);
    if (!retval)
        retval = sizeof(unsigned long);
out:
    __set_current_state(TASK_RUNNING);
    remove_wait_queue(&devp->hd_waitqueue, &wait);

    return retval;
}

static unsigned int hpet_poll(struct file *file, poll_table * wait)
{
    unsigned long v;
    struct hpet_dev *devp;

    devp = file->private_data;

    if (!devp->hd_ireqfreq)
        return 0;

    poll_wait(file, &devp->hd_waitqueue, wait);

    spin_lock_irq(&hpet_lock);
    v = devp->hd_irqdata;
    spin_unlock_irq(&hpet_lock);

    if (v != 0)
        return POLLIN | POLLRDNORM;

    return 0;
}

static int hpet_mmap(struct file *file, struct vm_area_struct *vma)
{
#ifdef  CONFIG_HPET_MMAP
    struct hpet_dev *devp;
    unsigned long addr;

    if (((vma->vm_end - vma->vm_start) != PAGE_SIZE) || vma->vm_pgoff)
        return -EINVAL;

    devp = file->private_data;
    addr = devp->hd_hpets->hp_hpet_phys;

    if (addr & (PAGE_SIZE - 1))
        return -ENOSYS;

    vma->vm_flags |= VM_IO;
    vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

    if (io_remap_pfn_range(vma, vma->vm_start, addr >> PAGE_SHIFT,
                    PAGE_SIZE, vma->vm_page_prot)) {
        printk(KERN_ERR "%s: io_remap_pfn_range failed\n",
            __func__);
        return -EAGAIN;
    }

    return 0;
#else
    return -ENOSYS;
#endif
}

static int hpet_fasync(int fd, struct file *file, int on)
{
    struct hpet_dev *devp;

    devp = file->private_data;

    if (fasync_helper(fd, file, on, &devp->hd_async_queue) >= 0)
        return 0;
    else
        return -EIO;
}

static int hpet_release(struct inode *inode, struct file *file)
{
    struct hpet_dev *devp;
    struct hpet_timer __iomem *timer;
    int irq = 0;

    devp = file->private_data;
    timer = devp->hd_timer;

    spin_lock_irq(&hpet_lock);

    writeq((readq(&timer->hpet_config) & ~Tn_INT_ENB_CNF_MASK),
           &timer->hpet_config);

    irq = devp->hd_irq;
    devp->hd_irq = 0;

    devp->hd_ireqfreq = 0;

    if (devp->hd_flags & HPET_PERIODIC
        && readq(&timer->hpet_config) & Tn_TYPE_CNF_MASK) {
        unsigned long v;

        v = readq(&timer->hpet_config);
        v ^= Tn_TYPE_CNF_MASK;
        writeq(v, &timer->hpet_config);
    }

    devp->hd_flags &= ~(HPET_OPEN | HPET_IE | HPET_PERIODIC);
    spin_unlock_irq(&hpet_lock);

    if (irq)
        free_irq(irq, devp);

    file->private_data = NULL;
    return 0;
}

static int hpet_ioctl_ieon(struct hpet_dev *devp)
{
    struct hpet_timer __iomem *timer;
    struct hpet __iomem *hpet;
    struct hpets *hpetp;
    int irq;
    unsigned long g, v, t, m;
    unsigned long flags, isr;

    timer = devp->hd_timer;
    hpet = devp->hd_hpet;
    hpetp = devp->hd_hpets;

    if (!devp->hd_ireqfreq)
        return -EIO;

    spin_lock_irq(&hpet_lock);

    if (devp->hd_flags & HPET_IE) {
        spin_unlock_irq(&hpet_lock);
        return -EBUSY;
    }

    devp->hd_flags |= HPET_IE;

    if (readl(&timer->hpet_config) & Tn_INT_TYPE_CNF_MASK)
        devp->hd_flags |= HPET_SHARED_IRQ;
    spin_unlock_irq(&hpet_lock);

    irq = devp->hd_hdwirq;

    if (irq) {
        unsigned long irq_flags;

        if (devp->hd_flags & HPET_SHARED_IRQ) {
            /*
             * To prevent the interrupt handler from seeing an
             * unwanted interrupt status bit, program the timer
             * so that it will not fire in the near future ...
             */
            writel(readl(&timer->hpet_config) & ~Tn_TYPE_CNF_MASK,
                   &timer->hpet_config);
            write_counter(read_counter(&hpet->hpet_mc),
                      &timer->hpet_compare);
            /* ... and clear any left-over status. */
            isr = 1 << (devp - devp->hd_hpets->hp_dev);
            writel(isr, &hpet->hpet_isr);
        }

        sprintf(devp->hd_name, "hpet%d", (int)(devp - hpetp->hp_dev));
        irq_flags = devp->hd_flags & HPET_SHARED_IRQ
                        ? IRQF_SHARED : IRQF_DISABLED;
        if (request_irq(irq, hpet_interrupt, irq_flags,
                devp->hd_name, (void *)devp)) {
            printk(KERN_ERR "hpet: IRQ %d is not free\n", irq);
            irq = 0;
        }
    }

    if (irq == 0) {
        spin_lock_irq(&hpet_lock);
        devp->hd_flags ^= HPET_IE;
        spin_unlock_irq(&hpet_lock);
        return -EIO;
    }

    devp->hd_irq = irq;
    t = devp->hd_ireqfreq;
    v = readq(&timer->hpet_config);

    /* 64-bit comparators are not yet supported through the ioctls,
     * so force this into 32-bit mode if it supports both modes
     */
    g = v | Tn_32MODE_CNF_MASK | Tn_INT_ENB_CNF_MASK;

    if (devp->hd_flags & HPET_PERIODIC) {
        g |= Tn_TYPE_CNF_MASK;
        v |= Tn_TYPE_CNF_MASK | Tn_VAL_SET_CNF_MASK;
        writeq(v, &timer->hpet_config);
        local_irq_save(flags);

        /*
         * NOTE: First we modify the hidden accumulator
         * register supported by periodic-capable comparators.
         * We never want to modify the (single) counter; that
         * would affect all the comparators. The value written
         * is the counter value when the first interrupt is due.
         */
        m = read_counter(&hpet->hpet_mc);
        write_counter(t + m + hpetp->hp_delta, &timer->hpet_compare);
        /*
         * Then we modify the comparator, indicating the period
         * for subsequent interrupt.
         */
        write_counter(t, &timer->hpet_compare);
    } else {
        local_irq_save(flags);
        m = read_counter(&hpet->hpet_mc);
        write_counter(t + m + hpetp->hp_delta, &timer->hpet_compare);
    }

    if (devp->hd_flags & HPET_SHARED_IRQ) {
        isr = 1 << (devp - devp->hd_hpets->hp_dev);
        writel(isr, &hpet->hpet_isr);
    }
    writeq(g, &timer->hpet_config);
    local_irq_restore(flags);

    return 0;
}

/* converts Hz to number of timer ticks */
static inline unsigned long hpet_time_div(struct hpets *hpets,
                      unsigned long dis)
{
    unsigned long long m;

    m = hpets->hp_tick_freq + (dis >> 1);
    do_div(m, dis);
    return (unsigned long)m;
}

static int
hpet_ioctl_common(struct hpet_dev *devp, int cmd, unsigned long arg,
          struct hpet_info *info)
{
    struct hpet_timer __iomem *timer;
    struct hpet __iomem *hpet;
    struct hpets *hpetp;
    int err;
    unsigned long v;

    switch (cmd) {
    case HPET_IE_OFF:
    case HPET_INFO:
    case HPET_EPI:
    case HPET_DPI:
    case HPET_IRQFREQ:
        timer = devp->hd_timer;
        hpet = devp->hd_hpet;
        hpetp = devp->hd_hpets;
        break;
    case HPET_IE_ON:
        return hpet_ioctl_ieon(devp);
    default:
        return -EINVAL;
    }

    err = 0;

    switch (cmd) {
    case HPET_IE_OFF:
        if ((devp->hd_flags & HPET_IE) == 0)
            break;
        v = readq(&timer->hpet_config);
        v &= ~Tn_INT_ENB_CNF_MASK;
        writeq(v, &timer->hpet_config);
        if (devp->hd_irq) {
            free_irq(devp->hd_irq, devp);
            devp->hd_irq = 0;
        }
        devp->hd_flags ^= HPET_IE;
        break;
    case HPET_INFO:
        {
            memset(info, 0, sizeof(*info));
            if (devp->hd_ireqfreq)
                info->hi_ireqfreq =
                    hpet_time_div(hpetp, devp->hd_ireqfreq);
            info->hi_flags =
                readq(&timer->hpet_config) & Tn_PER_INT_CAP_MASK;
            info->hi_hpet = hpetp->hp_which;
            info->hi_timer = devp - hpetp->hp_dev;
            break;
        }
    case HPET_EPI:
        v = readq(&timer->hpet_config);
        if ((v & Tn_PER_INT_CAP_MASK) == 0) {
            err = -ENXIO;
            break;
        }
        devp->hd_flags |= HPET_PERIODIC;
        break;
    case HPET_DPI:
        v = readq(&timer->hpet_config);
        if ((v & Tn_PER_INT_CAP_MASK) == 0) {
            err = -ENXIO;
            break;
        }
        if (devp->hd_flags & HPET_PERIODIC &&
            readq(&timer->hpet_config) & Tn_TYPE_CNF_MASK) {
            v = readq(&timer->hpet_config);
            v ^= Tn_TYPE_CNF_MASK;
            writeq(v, &timer->hpet_config);
        }
        devp->hd_flags &= ~HPET_PERIODIC;
        break;
    case HPET_IRQFREQ:
        if ((arg > hpet_max_freq) &&
            !capable(CAP_SYS_RESOURCE)) {
            err = -EACCES;
            break;
        }

        if (!arg) {
            err = -EINVAL;
            break;
        }

        devp->hd_ireqfreq = hpet_time_div(hpetp, arg);
    }

    return err;
}

static long
hpet_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    struct hpet_info info;
    int err;

    mutex_lock(&hpet_mutex);
    err = hpet_ioctl_common(file->private_data, cmd, arg, &info);
    mutex_unlock(&hpet_mutex);

    if ((cmd == HPET_INFO) && !err &&
        (copy_to_user((void __user *)arg, &info, sizeof(info))))
        err = -EFAULT;

    return err;
}

#ifdef CONFIG_COMPAT
struct compat_hpet_info {
    compat_ulong_t hi_ireqfreq; /* Hz */
    compat_ulong_t hi_flags;    /* information */
    unsigned short hi_hpet;
    unsigned short hi_timer;
};

static long
hpet_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    struct hpet_info info;
    int err;

    mutex_lock(&hpet_mutex);
    err = hpet_ioctl_common(file->private_data, cmd, arg, &info);
    mutex_unlock(&hpet_mutex);

    if ((cmd == HPET_INFO) && !err) {
        struct compat_hpet_info __user *u = compat_ptr(arg);
        if (put_user(info.hi_ireqfreq, &u->hi_ireqfreq) ||
            put_user(info.hi_flags, &u->hi_flags) ||
            put_user(info.hi_hpet, &u->hi_hpet) ||
            put_user(info.hi_timer, &u->hi_timer))
            err = -EFAULT;
    }

    return err;
}
#endif

static const struct file_operations hpet_fops = {
    .owner = THIS_MODULE,
    .llseek = no_llseek,
    .read = hpet_read,
    .poll = hpet_poll,
    .unlocked_ioctl = hpet_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl = hpet_compat_ioctl,
#endif
    .open = hpet_open,
    .release = hpet_release,
    .fasync = hpet_fasync,
    .mmap = hpet_mmap,
};

static int hpet_is_known(struct hpet_data *hdp)
{
    struct hpets *hpetp;

    for (hpetp = hpets; hpetp; hpetp = hpetp->hp_next)
        if (hpetp->hp_hpet_phys == hdp->hd_phys_address)
            return 1;

    return 0;
}

static ctl_table hpet_table[] = {
    {
     .procname = "max-user-freq",
     .data = &hpet_max_freq,
     .maxlen = sizeof(int),
     .mode = 0644,
     .proc_handler = proc_dointvec,
     },
    {}
};

static ctl_table hpet_root[] = {
    {
     .procname = "hpet",
     .maxlen = 0,
     .mode = 0555,
     .child = hpet_table,
     },
    {}
};

static ctl_table dev_root[] = {
    {
     .procname = "dev",
     .maxlen = 0,
     .mode = 0555,
     .child = hpet_root,
     },
    {}
};

static struct ctl_table_header *sysctl_header;

/*
 * Adjustment for when arming the timer with
 * initial conditions.  That is, main counter
 * ticks expired before interrupts are enabled.
 */
#define TICK_CALIBRATE  (1000UL)

static unsigned long __hpet_calibrate(struct hpets *hpetp)
{
    struct hpet_timer __iomem *timer = NULL;
    unsigned long t, m, count, i, flags, start;
    struct hpet_dev *devp;
    int j;
    struct hpet __iomem *hpet;

    for (j = 0, devp = hpetp->hp_dev; j < hpetp->hp_ntimer; j++, devp++)
        if ((devp->hd_flags & HPET_OPEN) == 0) {
            timer = devp->hd_timer;
            break;
        }

    if (!timer)
        return 0;

    hpet = hpetp->hp_hpet;
    t = read_counter(&timer->hpet_compare);

    i = 0;
    count = hpet_time_div(hpetp, TICK_CALIBRATE);

    local_irq_save(flags);

    start = read_counter(&hpet->hpet_mc);

    do {
        m = read_counter(&hpet->hpet_mc);
        write_counter(t + m + hpetp->hp_delta, &timer->hpet_compare);
    } while (i++, (m - start) < count);

    local_irq_restore(flags);

    return (m - start) / i;
}

static unsigned long hpet_calibrate(struct hpets *hpetp)
{
    unsigned long ret = -1;
    unsigned long tmp;

    /*
     * Try to calibrate until return value becomes stable small value.
     * If SMI interruption occurs in calibration loop, the return value
     * will be big. This avoids its impact.
     */
    for ( ; ; ) {
        tmp = __hpet_calibrate(hpetp);
        if (ret <= tmp)
            break;
        ret = tmp;
    }

    return ret;
}

int hpet_alloc(struct hpet_data *hdp)
{
    u64 cap, mcfg;
    struct hpet_dev *devp;
    u32 i, ntimer;
    struct hpets *hpetp;
    size_t siz;
    struct hpet __iomem *hpet;
    static struct hpets *last;
    unsigned long period;
    unsigned long long temp;
    u32 remainder;

    /*
     * hpet_alloc can be called by platform dependent code.
     * If platform dependent code has allocated the hpet that
     * ACPI has also reported, then we catch it here.
     */
    if (hpet_is_known(hdp)) {
        printk(KERN_DEBUG "%s: duplicate HPET ignored\n",
            __func__);
        return 0;
    }

    siz = sizeof(struct hpets) + ((hdp->hd_nirqs - 1) *
                      sizeof(struct hpet_dev));

    hpetp = kzalloc(siz, GFP_KERNEL);

    if (!hpetp)
        return -ENOMEM;

    hpetp->hp_which = hpet_nhpet++;
    hpetp->hp_hpet = hdp->hd_address;
    hpetp->hp_hpet_phys = hdp->hd_phys_address;

    hpetp->hp_ntimer = hdp->hd_nirqs;

    for (i = 0; i < hdp->hd_nirqs; i++)
        hpetp->hp_dev[i].hd_hdwirq = hdp->hd_irq[i];

    hpet = hpetp->hp_hpet;

    cap = readq(&hpet->hpet_cap);

    ntimer = ((cap & HPET_NUM_TIM_CAP_MASK) >> HPET_NUM_TIM_CAP_SHIFT) + 1;

    if (hpetp->hp_ntimer != ntimer) {
        printk(KERN_WARNING "hpet: number irqs doesn't agree"
               " with number of timers\n");
        kfree(hpetp);
        return -ENODEV;
    }

    if (last)
        last->hp_next = hpetp;
    else
        hpets = hpetp;

    last = hpetp;

    period = (cap & HPET_COUNTER_CLK_PERIOD_MASK) >>
        HPET_COUNTER_CLK_PERIOD_SHIFT; /* fs, 10^-15 */
    temp = 1000000000000000uLL; /* 10^15 femtoseconds per second */
    temp += period >> 1; /* round */
    do_div(temp, period);
    hpetp->hp_tick_freq = temp; /* ticks per second */

    printk(KERN_INFO "hpet%d: at MMIO 0x%lx, IRQ%s",
        hpetp->hp_which, hdp->hd_phys_address,
        hpetp->hp_ntimer > 1 ? "s" : "");
    for (i = 0; i < hpetp->hp_ntimer; i++)
        printk(KERN_CONT "%s %d", i > 0 ? "," : "", hdp->hd_irq[i]);
    printk(KERN_CONT "\n");

    temp = hpetp->hp_tick_freq;
    remainder = do_div(temp, 1000000);
    printk(KERN_INFO
        "hpet%u: %u comparators, %d-bit %u.%06u MHz counter\n",
        hpetp->hp_which, hpetp->hp_ntimer,
        cap & HPET_COUNTER_SIZE_MASK ? 64 : 32,
        (unsigned) temp, remainder);

    mcfg = readq(&hpet->hpet_config);
    if ((mcfg & HPET_ENABLE_CNF_MASK) == 0) {
        write_counter(0L, &hpet->hpet_mc);
        mcfg |= HPET_ENABLE_CNF_MASK;
        writeq(mcfg, &hpet->hpet_config);
    }

    for (i = 0, devp = hpetp->hp_dev; i < hpetp->hp_ntimer; i++, devp++) {
        struct hpet_timer __iomem *timer;

        timer = &hpet->hpet_timers[devp - hpetp->hp_dev];

        devp->hd_hpets = hpetp;
        devp->hd_hpet = hpet;
        devp->hd_timer = timer;

        /*
         * If the timer was reserved by platform code,
         * then make timer unavailable for opens.
         */
        if (hdp->hd_state & (1 << i)) {
            devp->hd_flags = HPET_OPEN;
            continue;
        }

        init_waitqueue_head(&devp->hd_waitqueue);
    }

    hpetp->hp_delta = hpet_calibrate(hpetp);

/* This clocksource driver currently only works on ia64 */
#ifdef CONFIG_IA64
    if (!hpet_clocksource) {
        hpet_mctr = (void __iomem *)&hpetp->hp_hpet->hpet_mc;
        clocksource_hpet.archdata.fsys_mmio = hpet_mctr;
        clocksource_register_hz(&clocksource_hpet, hpetp->hp_tick_freq);
        hpetp->hp_clocksource = &clocksource_hpet;
        hpet_clocksource = &clocksource_hpet;
    }
#endif

    return 0;
}

static acpi_status hpet_resources(struct acpi_resource *res, void *data)
{
    struct hpet_data *hdp;
    acpi_status status;
    struct acpi_resource_address64 addr;

    hdp = data;

    status = acpi_resource_to_address64(res, &addr);

    if (ACPI_SUCCESS(status)) {
        hdp->hd_phys_address = addr.minimum;
        hdp->hd_address = ioremap(addr.minimum, addr.address_length);

        if (hpet_is_known(hdp)) {
            iounmap(hdp->hd_address);
            return AE_ALREADY_EXISTS;
        }
    } else if (res->type == ACPI_RESOURCE_TYPE_FIXED_MEMORY32) {
        struct acpi_resource_fixed_memory32 *fixmem32;

        fixmem32 = &res->data.fixed_memory32;
        if (!fixmem32)
            return AE_NO_MEMORY;

        hdp->hd_phys_address = fixmem32->address;
        hdp->hd_address = ioremap(fixmem32->address,
                        HPET_RANGE_SIZE);

        if (hpet_is_known(hdp)) {
            iounmap(hdp->hd_address);
            return AE_ALREADY_EXISTS;
        }
    } else if (res->type == ACPI_RESOURCE_TYPE_EXTENDED_IRQ) {
        struct acpi_resource_extended_irq *irqp;
        int i, irq;

        irqp = &res->data.extended_irq;

        for (i = 0; i < irqp->interrupt_count; i++) {
            irq = acpi_register_gsi(NULL, irqp->interrupts[i],
                      irqp->triggering, irqp->polarity);
            if (irq < 0)
                return AE_ERROR;

            hdp->hd_irq[hdp->hd_nirqs] = irq;
            hdp->hd_nirqs++;
        }
    }

    return AE_OK;
}

static int hpet_acpi_add(struct acpi_device *device)
{
    acpi_status result;
    struct hpet_data data;

    memset(&data, 0, sizeof(data));

    result =
        acpi_walk_resources(device->handle, METHOD_NAME__CRS,
                hpet_resources, &data);

    if (ACPI_FAILURE(result))
        return -ENODEV;

    if (!data.hd_address || !data.hd_nirqs) {
        if (data.hd_address)
            iounmap(data.hd_address);
        printk("%s: no address or irqs in _CRS\n", __func__);
        return -ENODEV;
    }

    return hpet_alloc(&data);
}

static int hpet_acpi_remove(struct acpi_device *device, int type)
{
    /* XXX need to unregister clocksource, dealloc mem, etc */
    return -EINVAL;
}

static const struct acpi_device_id hpet_device_ids[] = {
    {"PNP0103", 0},
    {"", 0},
};
MODULE_DEVICE_TABLE(acpi, hpet_device_ids);

static struct acpi_driver hpet_acpi_driver = {
    .name = "hpet",
    .ids = hpet_device_ids,
    .ops = {
        .add = hpet_acpi_add,
        .remove = hpet_acpi_remove,
        },
};

static struct miscdevice hpet_misc = { HPET_MINOR, "hpet", &hpet_fops };

static int __init hpet_init(void)
{
    int result;

    result = misc_register(&hpet_misc);
    if (result < 0)
        return -ENODEV;

    sysctl_header = register_sysctl_table(dev_root);

    result = acpi_bus_register_driver(&hpet_acpi_driver);
    if (result < 0) {
        if (sysctl_header)
            unregister_sysctl_table(sysctl_header);
        misc_deregister(&hpet_misc);
        return result;
    }

    return 0;
}

static void __exit hpet_exit(void)
{
    acpi_bus_unregister_driver(&hpet_acpi_driver);

    if (sysctl_header)
        unregister_sysctl_table(sysctl_header);
    misc_deregister(&hpet_misc);

    return;
}

module_init(hpet_init);
module_exit(hpet_exit);
MODULE_AUTHOR("Bob Picco <[email protected]>");
MODULE_LICENSE("GPL");