// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * 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.

   */
  
  #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;

  #ifndef MODULE
  static void __init do_xor_register(struct xor_block_template *tmpl)
  {
  	tmpl->next = template_list;
  	template_list = tmpl;
  }
  
  static int __init register_xor_blocks(void)
  {
  	active_template = XOR_SELECT_TEMPLATE(NULL);
  
  	if (!active_template) {
  #define xor_speed	do_xor_register
  		// register all the templates and pick the first as the default
  		XOR_TRY_TEMPLATES;
  #undef xor_speed
  		active_template = template_list;
  	}
  	return 0;
  }
  #endif

  #define BENCH_SIZE	4096
  #define REPS		800U

  static void __init

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

  	int i, j;

  	ktime_t min, start, diff;

  
  	tmpl->next = template_list;
  	template_list = tmpl;

  	preempt_disable();

  	min = (ktime_t)S64_MAX;
  	for (i = 0; i < 3; i++) {
  		start = ktime_get();
  		for (j = 0; j < REPS; j++) {

  			mb(); /* prevent loop optimzation */

  			tmpl->do_2(BENCH_SIZE, b1, b2);
  			mb();

  		}

  		diff = ktime_sub(ktime_get(), start);
  		if (diff < min)
  			min = diff;

  	}

  	preempt_enable();

  	// bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]
  	speed = (1000 * REPS * BENCH_SIZE) / (unsigned int)ktime_to_ns(min);

  	tmpl->speed = speed;

  	pr_info("   %-16s: %5d MB/sec
  ", tmpl->name, speed);

  }

  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;
  	}

  	b1 = (void *) __get_free_pages(GFP_KERNEL, 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
  ");

  	template_list = NULL;

  	XOR_TRY_TEMPLATES;
  	fastest = template_list;
  	for (f = fastest; f; f = f->next)
  		if (f->speed > fastest->speed)
  			fastest = f;

  	pr_info("xor: using function: %s (%d MB/sec)
  ",
  	       fastest->name, fastest->speed);

  
  #undef xor_speed
  
  	free_pages((unsigned long)b1, 2);

  out:

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

  MODULE_LICENSE("GPL");

  #ifndef MODULE

  /* when built-in xor.o must initialize before drivers/md/md.o */

  core_initcall(register_xor_blocks);
  #endif
  
  module_init(calibrate_xor_blocks);

  module_exit(xor_exit);