/*
   * xor.c : Multiple Devices driver for Linux
   *
   * Copyright (C) 1996, 1997, 1998, 1999, 2000,
   * Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.
   *
   * Dispatch optimized RAID-5 checksumming functions.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2, or (at your option)
   * any later version.
   *
   * You should have received a copy of the GNU General Public License
   * (for example /usr/src/linux/COPYING); if not, write to the Free
   * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  #define BH_TRACE 0
  #include <linux/module.h>

  #include <linux/gfp.h>

  #include <linux/raid/xor.h>

  #include <linux/jiffies.h>

  #include <linux/preempt.h>

  #include <asm/xor.h>

  #ifndef XOR_SELECT_TEMPLATE
  #define XOR_SELECT_TEMPLATE(x) (x)
  #endif

  /* The xor routines to use.  */
  static struct xor_block_template *active_template;
  
  void

  xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)

  {

  	unsigned long *p1, *p2, *p3, *p4;

  	p1 = (unsigned long *) srcs[0];
  	if (src_count == 1) {
  		active_template->do_2(bytes, dest, p1);

  		return;
  	}

  	p2 = (unsigned long *) srcs[1];
  	if (src_count == 2) {
  		active_template->do_3(bytes, dest, p1, p2);

  		return;
  	}

  	p3 = (unsigned long *) srcs[2];
  	if (src_count == 3) {
  		active_template->do_4(bytes, dest, p1, p2, p3);

  		return;
  	}

  	p4 = (unsigned long *) srcs[3];
  	active_template->do_5(bytes, dest, p1, p2, p3, p4);

  }

  EXPORT_SYMBOL(xor_blocks);

  
  /* Set of all registered templates.  */

  static struct xor_block_template *__initdata template_list;

  
  #define BENCH_SIZE (PAGE_SIZE)

  static void __init

  do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
  {
  	int speed;

  	unsigned long now, j;

  	int i, count, max;
  
  	tmpl->next = template_list;
  	template_list = tmpl;

  	preempt_disable();

  	/*
  	 * Count the number of XORs done during a whole jiffy, and use
  	 * this to calculate the speed of checksumming.  We use a 2-page
  	 * allocation to have guaranteed color L1-cache layout.
  	 */
  	max = 0;
  	for (i = 0; i < 5; i++) {

  		j = jiffies;

  		count = 0;

  		while ((now = jiffies) == j)
  			cpu_relax();
  		while (time_before(jiffies, now + 1)) {

  			mb(); /* prevent loop optimzation */

  			tmpl->do_2(BENCH_SIZE, b1, b2);
  			mb();
  			count++;
  			mb();
  		}
  		if (count > max)
  			max = count;
  	}

  	preempt_enable();

  	speed = max * (HZ * BENCH_SIZE / 1024);
  	tmpl->speed = speed;

  	printk(KERN_INFO "   %-10s: %5d.%03d MB/sec
  ", tmpl->name,

  	       speed / 1000, speed % 1000);
  }

  static int __init
  calibrate_xor_blocks(void)

  {
  	void *b1, *b2;
  	struct xor_block_template *f, *fastest;

  	fastest = XOR_SELECT_TEMPLATE(NULL);

  	if (fastest) {
  		printk(KERN_INFO "xor: automatically using best "
  				 "checksumming function   %-10s
  ",
  		       fastest->name);
  		goto out;
  	}

  	/*
  	 * Note: Since the memory is not actually used for _anything_ but to
  	 * test the XOR speed, we don't really want kmemcheck to warn about
  	 * reading uninitialized bytes here.
  	 */
  	b1 = (void *) __get_free_pages(GFP_KERNEL | __GFP_NOTRACK, 2);

  	if (!b1) {
  		printk(KERN_WARNING "xor: Yikes!  No memory available.
  ");

  		return -ENOMEM;
  	}
  	b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
  
  	/*

  	 * If this arch/cpu has a short-circuited selection, don't loop through
  	 * all the possible functions, just test the best one

  	 */

  #define xor_speed(templ)	do_xor_speed((templ), b1, b2)

  	printk(KERN_INFO "xor: measuring software checksum speed
  ");
  	XOR_TRY_TEMPLATES;
  	fastest = template_list;
  	for (f = fastest; f; f = f->next)
  		if (f->speed > fastest->speed)
  			fastest = f;

  	printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)
  ",

  	       fastest->name, fastest->speed / 1000, fastest->speed % 1000);
  
  #undef xor_speed
  
  	free_pages((unsigned long)b1, 2);

  out:

  	active_template = fastest;
  	return 0;
  }
  
  static __exit void xor_exit(void) { }

  MODULE_LICENSE("GPL");

  /* when built-in xor.o must initialize before drivers/md/md.o */
  core_initcall(calibrate_xor_blocks);

  module_exit(xor_exit);