linux/drivers/char/uv_mmtimer.c
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   1/*
   2 * Timer device implementation for SGI UV platform.
   3 *
   4 * This file is subject to the terms and conditions of the GNU General Public
   5 * License.  See the file "COPYING" in the main directory of this archive
   6 * for more details.
   7 *
   8 * Copyright (c) 2009 Silicon Graphics, Inc.  All rights reserved.
   9 *
  10 */
  11
  12#include <linux/types.h>
  13#include <linux/kernel.h>
  14#include <linux/ioctl.h>
  15#include <linux/module.h>
  16#include <linux/init.h>
  17#include <linux/errno.h>
  18#include <linux/mm.h>
  19#include <linux/fs.h>
  20#include <linux/mmtimer.h>
  21#include <linux/miscdevice.h>
  22#include <linux/posix-timers.h>
  23#include <linux/interrupt.h>
  24#include <linux/time.h>
  25#include <linux/math64.h>
  26
  27#include <asm/genapic.h>
  28#include <asm/uv/uv_hub.h>
  29#include <asm/uv/bios.h>
  30#include <asm/uv/uv.h>
  31
  32MODULE_AUTHOR("Dimitri Sivanich <sivanich@sgi.com>");
  33MODULE_DESCRIPTION("SGI UV Memory Mapped RTC Timer");
  34MODULE_LICENSE("GPL");
  35
  36/* name of the device, usually in /dev */
  37#define UV_MMTIMER_NAME "mmtimer"
  38#define UV_MMTIMER_DESC "SGI UV Memory Mapped RTC Timer"
  39#define UV_MMTIMER_VERSION "1.0"
  40
  41static long uv_mmtimer_ioctl(struct file *file, unsigned int cmd,
  42                                                unsigned long arg);
  43static int uv_mmtimer_mmap(struct file *file, struct vm_area_struct *vma);
  44
  45/*
  46 * Period in femtoseconds (10^-15 s)
  47 */
  48static unsigned long uv_mmtimer_femtoperiod;
  49
  50static const struct file_operations uv_mmtimer_fops = {
  51        .owner = THIS_MODULE,
  52        .mmap = uv_mmtimer_mmap,
  53        .unlocked_ioctl = uv_mmtimer_ioctl,
  54        .llseek = noop_llseek,
  55};
  56
  57/**
  58 * uv_mmtimer_ioctl - ioctl interface for /dev/uv_mmtimer
  59 * @file: file structure for the device
  60 * @cmd: command to execute
  61 * @arg: optional argument to command
  62 *
  63 * Executes the command specified by @cmd.  Returns 0 for success, < 0 for
  64 * failure.
  65 *
  66 * Valid commands:
  67 *
  68 * %MMTIMER_GETOFFSET - Should return the offset (relative to the start
  69 * of the page where the registers are mapped) for the counter in question.
  70 *
  71 * %MMTIMER_GETRES - Returns the resolution of the clock in femto (10^-15)
  72 * seconds
  73 *
  74 * %MMTIMER_GETFREQ - Copies the frequency of the clock in Hz to the address
  75 * specified by @arg
  76 *
  77 * %MMTIMER_GETBITS - Returns the number of bits in the clock's counter
  78 *
  79 * %MMTIMER_MMAPAVAIL - Returns 1 if registers can be mmap'd into userspace
  80 *
  81 * %MMTIMER_GETCOUNTER - Gets the current value in the counter and places it
  82 * in the address specified by @arg.
  83 */
  84static long uv_mmtimer_ioctl(struct file *file, unsigned int cmd,
  85                                                unsigned long arg)
  86{
  87        int ret = 0;
  88
  89        switch (cmd) {
  90        case MMTIMER_GETOFFSET: /* offset of the counter */
  91                /*
  92                 * Starting with HUB rev 2.0, the UV RTC register is
  93                 * replicated across all cachelines of it's own page.
  94                 * This allows faster simultaneous reads from a given socket.
  95                 *
  96                 * The offset returned is in 64 bit units.
  97                 */
  98                if (uv_get_min_hub_revision_id() == 1)
  99                        ret = 0;
 100                else
 101                        ret = ((uv_blade_processor_id() * L1_CACHE_BYTES) %
 102                                        PAGE_SIZE) / 8;
 103                break;
 104
 105        case MMTIMER_GETRES: /* resolution of the clock in 10^-15 s */
 106                if (copy_to_user((unsigned long __user *)arg,
 107                                &uv_mmtimer_femtoperiod, sizeof(unsigned long)))
 108                        ret = -EFAULT;
 109                break;
 110
 111        case MMTIMER_GETFREQ: /* frequency in Hz */
 112                if (copy_to_user((unsigned long __user *)arg,
 113                                &sn_rtc_cycles_per_second,
 114                                sizeof(unsigned long)))
 115                        ret = -EFAULT;
 116                break;
 117
 118        case MMTIMER_GETBITS: /* number of bits in the clock */
 119                ret = hweight64(UVH_RTC_REAL_TIME_CLOCK_MASK);
 120                break;
 121
 122        case MMTIMER_MMAPAVAIL:
 123                ret = 1;
 124                break;
 125
 126        case MMTIMER_GETCOUNTER:
 127                if (copy_to_user((unsigned long __user *)arg,
 128                                (unsigned long *)uv_local_mmr_address(UVH_RTC),
 129                                sizeof(unsigned long)))
 130                        ret = -EFAULT;
 131                break;
 132        default:
 133                ret = -ENOTTY;
 134                break;
 135        }
 136        return ret;
 137}
 138
 139/**
 140 * uv_mmtimer_mmap - maps the clock's registers into userspace
 141 * @file: file structure for the device
 142 * @vma: VMA to map the registers into
 143 *
 144 * Calls remap_pfn_range() to map the clock's registers into
 145 * the calling process' address space.
 146 */
 147static int uv_mmtimer_mmap(struct file *file, struct vm_area_struct *vma)
 148{
 149        unsigned long uv_mmtimer_addr;
 150
 151        if (vma->vm_end - vma->vm_start != PAGE_SIZE)
 152                return -EINVAL;
 153
 154        if (vma->vm_flags & VM_WRITE)
 155                return -EPERM;
 156
 157        if (PAGE_SIZE > (1 << 16))
 158                return -ENOSYS;
 159
 160        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 161
 162        uv_mmtimer_addr = UV_LOCAL_MMR_BASE | UVH_RTC;
 163        uv_mmtimer_addr &= ~(PAGE_SIZE - 1);
 164        uv_mmtimer_addr &= 0xfffffffffffffffUL;
 165
 166        if (remap_pfn_range(vma, vma->vm_start, uv_mmtimer_addr >> PAGE_SHIFT,
 167                                        PAGE_SIZE, vma->vm_page_prot)) {
 168                printk(KERN_ERR "remap_pfn_range failed in uv_mmtimer_mmap\n");
 169                return -EAGAIN;
 170        }
 171
 172        return 0;
 173}
 174
 175static struct miscdevice uv_mmtimer_miscdev = {
 176        MISC_DYNAMIC_MINOR,
 177        UV_MMTIMER_NAME,
 178        &uv_mmtimer_fops
 179};
 180
 181
 182/**
 183 * uv_mmtimer_init - device initialization routine
 184 *
 185 * Does initial setup for the uv_mmtimer device.
 186 */
 187static int __init uv_mmtimer_init(void)
 188{
 189        if (!is_uv_system()) {
 190                printk(KERN_ERR "%s: Hardware unsupported\n", UV_MMTIMER_NAME);
 191                return -1;
 192        }
 193
 194        /*
 195         * Sanity check the cycles/sec variable
 196         */
 197        if (sn_rtc_cycles_per_second < 100000) {
 198                printk(KERN_ERR "%s: unable to determine clock frequency\n",
 199                       UV_MMTIMER_NAME);
 200                return -1;
 201        }
 202
 203        uv_mmtimer_femtoperiod = ((unsigned long)1E15 +
 204                                sn_rtc_cycles_per_second / 2) /
 205                                sn_rtc_cycles_per_second;
 206
 207        if (misc_register(&uv_mmtimer_miscdev)) {
 208                printk(KERN_ERR "%s: failed to register device\n",
 209                       UV_MMTIMER_NAME);
 210                return -1;
 211        }
 212
 213        printk(KERN_INFO "%s: v%s, %ld MHz\n", UV_MMTIMER_DESC,
 214                UV_MMTIMER_VERSION,
 215                sn_rtc_cycles_per_second/(unsigned long)1E6);
 216
 217        return 0;
 218}
 219
 220module_init(uv_mmtimer_init);
 221
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