/*
   * 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 <sivanich@sgi.com>");
  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,
  };
  
  /**
   * uv_mmtimer_ioctl - ioctl interface for /dev/uv_mmtimer
   * @file: file structure for the device
   * @cmd: command to execute
   * @arg: optional argument to command
   *
   * Executes the command specified by @cmd.  Returns 0 for success, < 0 for
   * failure.
   *
   * Valid commands:
   *
   * %MMTIMER_GETOFFSET - Should return the offset (relative to the start
   * of the page where the registers are mapped) for the counter in question.
   *
   * %MMTIMER_GETRES - Returns the resolution of the clock in femto (10^-15)
   * seconds
   *
   * %MMTIMER_GETFREQ - Copies the frequency of the clock in Hz to the address
   * specified by @arg
   *
   * %MMTIMER_GETBITS - Returns the number of bits in the clock's counter
   *
   * %MMTIMER_MMAPAVAIL - Returns 1 if registers can be mmap'd into userspace
   *
   * %MMTIMER_GETCOUNTER - Gets the current value in the counter and places it
   * in the address specified by @arg.
   */
  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;
  }
  
  /**
   * uv_mmtimer_mmap - maps the clock's registers into userspace
   * @file: file structure for the device
   * @vma: VMA to map the registers into
   *
   * Calls remap_pfn_range() to map the clock's registers into
   * the calling process' address space.
   */
  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
  ");
  		return -EAGAIN;
  	}
  
  	return 0;
  }
  
  static struct miscdevice uv_mmtimer_miscdev = {
  	MISC_DYNAMIC_MINOR,
  	UV_MMTIMER_NAME,
  	&uv_mmtimer_fops
  };
  
  
  /**
   * uv_mmtimer_init - device initialization routine
   *
   * Does initial setup for the uv_mmtimer device.
   */
  static int __init uv_mmtimer_init(void)
  {
  	if (!is_uv_system()) {
  		printk(KERN_ERR "%s: Hardware unsupported
  ", 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
  ",
  		       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
  ",
  		       UV_MMTIMER_NAME);
  		return -1;
  	}
  
  	printk(KERN_INFO "%s: v%s, %ld MHz
  ", UV_MMTIMER_DESC,
  		UV_MMTIMER_VERSION,
  		sn_rtc_cycles_per_second/(unsigned long)1E6);
  
  	return 0;
  }
  
  module_init(uv_mmtimer_init);