/* -*- linux-c -*- ------------------------------------------------------- *
   *
   *   Copyright 2002 H. Peter Anvin - All Rights Reserved
   *
   *   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, Inc., 53 Temple Place Ste 330,

   *   Boston MA 02111-1307, USA; either version 2 of the License, or

   *   (at your option) any later version; incorporated herein by reference.
   *
   * ----------------------------------------------------------------------- */
  
  /*

   * raid6/algos.c

   *
   * Algorithm list and algorithm selection for RAID-6
   */

  #include <linux/raid/pq.h>

  #include <linux/module.h>

  #ifndef __KERNEL__
  #include <sys/mman.h>

  #include <stdio.h>

  #else

  #include <linux/gfp.h>

  #if !RAID6_USE_EMPTY_ZERO_PAGE
  /* In .bss so it's zeroed */
  const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
  EXPORT_SYMBOL(raid6_empty_zero_page);
  #endif

  #endif
  
  struct raid6_calls raid6_call;

  EXPORT_SYMBOL_GPL(raid6_call);

  const struct raid6_calls * const raid6_algos[] = {
  	&raid6_intx1,
  	&raid6_intx2,
  	&raid6_intx4,
  	&raid6_intx8,
  #if defined(__ia64__)
  	&raid6_intx16,
  	&raid6_intx32,
  #endif

  #if defined(__i386__) && !defined(__arch_um__)

  	&raid6_mmxx1,
  	&raid6_mmxx2,
  	&raid6_sse1x1,
  	&raid6_sse1x2,
  	&raid6_sse2x1,
  	&raid6_sse2x2,
  #endif

  #if defined(__x86_64__) && !defined(__arch_um__)

  	&raid6_sse2x1,
  	&raid6_sse2x2,
  	&raid6_sse2x4,
  #endif
  #ifdef CONFIG_ALTIVEC
  	&raid6_altivec1,
  	&raid6_altivec2,
  	&raid6_altivec4,
  	&raid6_altivec8,
  #endif
  	NULL
  };
  
  #ifdef __KERNEL__
  #define RAID6_TIME_JIFFIES_LG2	4
  #else
  /* Need more time to be stable in userspace */
  #define RAID6_TIME_JIFFIES_LG2	9

  #define time_before(x, y) ((x) < (y))

  #endif
  
  /* Try to pick the best algorithm */
  /* This code uses the gfmul table as convenient data set to abuse */
  
  int __init raid6_select_algo(void)
  {
  	const struct raid6_calls * const * algo;
  	const struct raid6_calls * best;
  	char *syndromes;
  	void *dptrs[(65536/PAGE_SIZE)+2];
  	int i, disks;
  	unsigned long perf, bestperf;
  	int bestprefer;
  	unsigned long j0, j1;
  
  	disks = (65536/PAGE_SIZE)+2;
  	for ( i = 0 ; i < disks-2 ; i++ ) {
  		dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
  	}
  
  	/* Normal code - use a 2-page allocation to avoid D$ conflict */
  	syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
  
  	if ( !syndromes ) {
  		printk("raid6: Yikes!  No memory available.
  ");
  		return -ENOMEM;
  	}
  
  	dptrs[disks-2] = syndromes;
  	dptrs[disks-1] = syndromes + PAGE_SIZE;
  
  	bestperf = 0;  bestprefer = 0;  best = NULL;
  
  	for ( algo = raid6_algos ; *algo ; algo++ ) {
  		if ( !(*algo)->valid || (*algo)->valid() ) {
  			perf = 0;
  
  			preempt_disable();
  			j0 = jiffies;
  			while ( (j1 = jiffies) == j0 )
  				cpu_relax();

  			while (time_before(jiffies,
  					    j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {

  				(*algo)->gen_syndrome(disks, PAGE_SIZE, dptrs);
  				perf++;
  			}
  			preempt_enable();
  
  			if ( (*algo)->prefer > bestprefer ||
  			     ((*algo)->prefer == bestprefer &&
  			      perf > bestperf) ) {
  				best = *algo;
  				bestprefer = best->prefer;
  				bestperf = perf;
  			}
  			printk("raid6: %-8s %5ld MB/s
  ", (*algo)->name,
  			       (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
  		}
  	}

  	if (best) {

  		printk("raid6: using algorithm %s (%ld MB/s)
  ",
  		       best->name,
  		       (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));

  		raid6_call = *best;
  	} else

  		printk("raid6: Yikes!  No algorithm found!
  ");

  	free_pages((unsigned long)syndromes, 1);
  
  	return best ? 0 : -EINVAL;
  }

  
  static void raid6_exit(void)
  {
  	do { } while (0);
  }
  
  subsys_initcall(raid6_select_algo);
  module_exit(raid6_exit);
  MODULE_LICENSE("GPL");

  MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");