1/*
2 * xor.c : Multiple Devices driver for Linux
3 *
4 * Copyright (C) 1996, 1997, 1998, 1999, 2000,
5 * Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.
6 *
7 * Dispatch optimized RAID-5 checksumming functions.
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2, or (at your option)
12 * any later version.
13 *
14 * You should have received a copy of the GNU General Public License
15 * (for example /usr/src/linux/COPYING); if not, write to the Free
16 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
17 */
18
19#define BH_TRACE 0
20#include <linux/module.h>
21#include <linux/gfp.h>
22#include <linux/raid/xor.h>
23#include <linux/jiffies.h>
24#include <asm/xor.h>
25
26/* The xor routines to use.  */
27static struct xor_block_template *active_template;
28
29void
30xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
31{
32	unsigned long *p1, *p2, *p3, *p4;
33
34	p1 = (unsigned long *) srcs[0];
35	if (src_count == 1) {
36		active_template->do_2(bytes, dest, p1);
37		return;
38	}
39
40	p2 = (unsigned long *) srcs[1];
41	if (src_count == 2) {
42		active_template->do_3(bytes, dest, p1, p2);
43		return;
44	}
45
46	p3 = (unsigned long *) srcs[2];
47	if (src_count == 3) {
48		active_template->do_4(bytes, dest, p1, p2, p3);
49		return;
50	}
51
52	p4 = (unsigned long *) srcs[3];
53	active_template->do_5(bytes, dest, p1, p2, p3, p4);
54}
55EXPORT_SYMBOL(xor_blocks);
56
57/* Set of all registered templates.  */
58static struct xor_block_template *template_list;
59
60#define BENCH_SIZE (PAGE_SIZE)
61
62static void
63do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
64{
65	int speed;
66	unsigned long now;
67	int i, count, max;
68
69	tmpl->next = template_list;
70	template_list = tmpl;
71
72	/*
73	 * Count the number of XORs done during a whole jiffy, and use
74	 * this to calculate the speed of checksumming.  We use a 2-page
75	 * allocation to have guaranteed color L1-cache layout.
76	 */
77	max = 0;
78	for (i = 0; i < 5; i++) {
79		now = jiffies;
80		count = 0;
81		while (jiffies == now) {
82			mb(); /* prevent loop optimzation */
83			tmpl->do_2(BENCH_SIZE, b1, b2);
84			mb();
85			count++;
86			mb();
87		}
88		if (count > max)
89			max = count;
90	}
91
92	speed = max * (HZ * BENCH_SIZE / 1024);
93	tmpl->speed = speed;
94
95	printk(KERN_INFO "   %-10s: %5d.%03d MB/sec\n", tmpl->name,
96	       speed / 1000, speed % 1000);
97}
98
99static int __init
100calibrate_xor_blocks(void)
101{
102	void *b1, *b2;
103	struct xor_block_template *f, *fastest;
104
105	/*
106	 * Note: Since the memory is not actually used for _anything_ but to
107	 * test the XOR speed, we don't really want kmemcheck to warn about
108	 * reading uninitialized bytes here.
109	 */
110	b1 = (void *) __get_free_pages(GFP_KERNEL | __GFP_NOTRACK, 2);
111	if (!b1) {
112		printk(KERN_WARNING "xor: Yikes!  No memory available.\n");
113		return -ENOMEM;
114	}
115	b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
116
117	/*
118	 * If this arch/cpu has a short-circuited selection, don't loop through
119	 * all the possible functions, just test the best one
120	 */
121
122	fastest = NULL;
123
124#ifdef XOR_SELECT_TEMPLATE
125		fastest = XOR_SELECT_TEMPLATE(fastest);
126#endif
127
128#define xor_speed(templ)	do_xor_speed((templ), b1, b2)
129
130	if (fastest) {
131		printk(KERN_INFO "xor: automatically using best "
132			"checksumming function: %s\n",
133			fastest->name);
134		xor_speed(fastest);
135	} else {
136		printk(KERN_INFO "xor: measuring software checksum speed\n");
137		XOR_TRY_TEMPLATES;
138		fastest = template_list;
139		for (f = fastest; f; f = f->next)
140			if (f->speed > fastest->speed)
141				fastest = f;
142	}
143
144	printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
145	       fastest->name, fastest->speed / 1000, fastest->speed % 1000);
146
147#undef xor_speed
148
149	free_pages((unsigned long)b1, 2);
150
151	active_template = fastest;
152	return 0;
153}
154
155static __exit void xor_exit(void) { }
156
157MODULE_LICENSE("GPL");
158
159/* when built-in xor.o must initialize before drivers/md/md.o */
160core_initcall(calibrate_xor_blocks);
161module_exit(xor_exit);
162