uv_mmtimer.c

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/*
 * Timer device implementation for SGI UV platform.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (c) 2009 Silicon Graphics, Inc.  All rights reserved.
 *
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/ioctl.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/mmtimer.h>
#include <linux/miscdevice.h>
#include <linux/posix-timers.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/math64.h>

#include <asm/genapic.h>
#include <asm/uv/uv_hub.h>
#include <asm/uv/bios.h>
#include <asm/uv/uv.h>

MODULE_AUTHOR("Dimitri Sivanich <[email protected]>");
MODULE_DESCRIPTION("SGI UV Memory Mapped RTC Timer");
MODULE_LICENSE("GPL");

/* name of the device, usually in /dev */
#define UV_MMTIMER_NAME "mmtimer"
#define UV_MMTIMER_DESC "SGI UV Memory Mapped RTC Timer"
#define UV_MMTIMER_VERSION "1.0"

static long uv_mmtimer_ioctl(struct file *file, unsigned int cmd,
                        unsigned long arg);
static int uv_mmtimer_mmap(struct file *file, struct vm_area_struct *vma);

/*
 * Period in femtoseconds (10^-15 s)
 */
static unsigned long uv_mmtimer_femtoperiod;

static const struct file_operations uv_mmtimer_fops = {
    .owner = THIS_MODULE,
    .mmap = uv_mmtimer_mmap,
    .unlocked_ioctl = uv_mmtimer_ioctl,
    .llseek = noop_llseek,
};

static long uv_mmtimer_ioctl(struct file *file, unsigned int cmd,
                        unsigned long arg)
{
    int ret = 0;

    switch (cmd) {
    case MMTIMER_GETOFFSET: /* offset of the counter */
        /*
         * Starting with HUB rev 2.0, the UV RTC register is
         * replicated across all cachelines of it's own page.
         * This allows faster simultaneous reads from a given socket.
         *
         * The offset returned is in 64 bit units.
         */
        if (uv_get_min_hub_revision_id() == 1)
            ret = 0;
        else
            ret = ((uv_blade_processor_id() * L1_CACHE_BYTES) %
                    PAGE_SIZE) / 8;
        break;

    case MMTIMER_GETRES: /* resolution of the clock in 10^-15 s */
        if (copy_to_user((unsigned long __user *)arg,
                &uv_mmtimer_femtoperiod, sizeof(unsigned long)))
            ret = -EFAULT;
        break;

    case MMTIMER_GETFREQ: /* frequency in Hz */
        if (copy_to_user((unsigned long __user *)arg,
                &sn_rtc_cycles_per_second,
                sizeof(unsigned long)))
            ret = -EFAULT;
        break;

    case MMTIMER_GETBITS: /* number of bits in the clock */
        ret = hweight64(UVH_RTC_REAL_TIME_CLOCK_MASK);
        break;

    case MMTIMER_MMAPAVAIL:
        ret = 1;
        break;

    case MMTIMER_GETCOUNTER:
        if (copy_to_user((unsigned long __user *)arg,
                (unsigned long *)uv_local_mmr_address(UVH_RTC),
                sizeof(unsigned long)))
            ret = -EFAULT;
        break;
    default:
        ret = -ENOTTY;
        break;
    }
    return ret;
}

static int uv_mmtimer_mmap(struct file *file, struct vm_area_struct *vma)
{
    unsigned long uv_mmtimer_addr;

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

    if (vma->vm_flags & VM_WRITE)
        return -EPERM;

    if (PAGE_SIZE > (1 << 16))
        return -ENOSYS;

    vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

    uv_mmtimer_addr = UV_LOCAL_MMR_BASE | UVH_RTC;
    uv_mmtimer_addr &= ~(PAGE_SIZE - 1);
    uv_mmtimer_addr &= 0xfffffffffffffffUL;

    if (remap_pfn_range(vma, vma->vm_start, uv_mmtimer_addr >> PAGE_SHIFT,
                    PAGE_SIZE, vma->vm_page_prot)) {
        printk(KERN_ERR "remap_pfn_range failed in uv_mmtimer_mmap\n");
        return -EAGAIN;
    }

    return 0;
}

static struct miscdevice uv_mmtimer_miscdev = {
    MISC_DYNAMIC_MINOR,
    UV_MMTIMER_NAME,
    &uv_mmtimer_fops
};


static int __init uv_mmtimer_init(void)
{
    if (!is_uv_system()) {
        printk(KERN_ERR "%s: Hardware unsupported\n", UV_MMTIMER_NAME);
        return -1;
    }

    /*
     * Sanity check the cycles/sec variable
     */
    if (sn_rtc_cycles_per_second < 100000) {
        printk(KERN_ERR "%s: unable to determine clock frequency\n",
               UV_MMTIMER_NAME);
        return -1;
    }

    uv_mmtimer_femtoperiod = ((unsigned long)1E15 +
                sn_rtc_cycles_per_second / 2) /
                sn_rtc_cycles_per_second;

    if (misc_register(&uv_mmtimer_miscdev)) {
        printk(KERN_ERR "%s: failed to register device\n",
               UV_MMTIMER_NAME);
        return -1;
    }

    printk(KERN_INFO "%s: v%s, %ld MHz\n", UV_MMTIMER_DESC,
        UV_MMTIMER_VERSION,
        sn_rtc_cycles_per_second/(unsigned long)1E6);

    return 0;
}

module_init(uv_mmtimer_init);