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 <linux/preempt.h>
25#include <asm/xor.h>
26
27/* The xor routines to use.  */
28static struct xor_block_template *active_template;
29
30void
31xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
32{
33	unsigned long *p1, *p2, *p3, *p4;
34
35	p1 = (unsigned long *) srcs[0];
36	if (src_count == 1) {
37		active_template->do_2(bytes, dest, p1);
38		return;
39	}
40
41	p2 = (unsigned long *) srcs[1];
42	if (src_count == 2) {
43		active_template->do_3(bytes, dest, p1, p2);
44		return;
45	}
46
47	p3 = (unsigned long *) srcs[2];
48	if (src_count == 3) {
49		active_template->do_4(bytes, dest, p1, p2, p3);
50		return;
51	}
52
53	p4 = (unsigned long *) srcs[3];
54	active_template->do_5(bytes, dest, p1, p2, p3, p4);
55}
56EXPORT_SYMBOL(xor_blocks);
57
58/* Set of all registered templates.  */
59static struct xor_block_template *__initdata template_list;
60
61#define BENCH_SIZE (PAGE_SIZE)
62
63static void __init
64do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
65{
66	int speed;
67	unsigned long now, j;
68	int i, count, max;
69
70	tmpl->next = template_list;
71	template_list = tmpl;
72
73	preempt_disable();
74
75	/*
76	 * Count the number of XORs done during a whole jiffy, and use
77	 * this to calculate the speed of checksumming.  We use a 2-page
78	 * allocation to have guaranteed color L1-cache layout.
79	 */
80	max = 0;
81	for (i = 0; i < 5; i++) {
82		j = jiffies;
83		count = 0;
84		while ((now = jiffies) == j)
85			cpu_relax();
86		while (time_before(jiffies, now + 1)) {
87			mb(); /* prevent loop optimzation */
88			tmpl->do_2(BENCH_SIZE, b1, b2);
89			mb();
90			count++;
91			mb();
92		}
93		if (count > max)
94			max = count;
95	}
96
97	preempt_enable();
98
99	speed = max * (HZ * BENCH_SIZE / 1024);
100	tmpl->speed = speed;
101
102	printk(KERN_INFO "   %-10s: %5d.%03d MB/sec\n", tmpl->name,
103	       speed / 1000, speed % 1000);
104}
105
106static int __init
107calibrate_xor_blocks(void)
108{
109	void *b1, *b2;
110	struct xor_block_template *f, *fastest;
111
112	/*
113	 * Note: Since the memory is not actually used for _anything_ but to
114	 * test the XOR speed, we don't really want kmemcheck to warn about
115	 * reading uninitialized bytes here.
116	 */
117	b1 = (void *) __get_free_pages(GFP_KERNEL | __GFP_NOTRACK, 2);
118	if (!b1) {
119		printk(KERN_WARNING "xor: Yikes!  No memory available.\n");
120		return -ENOMEM;
121	}
122	b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
123
124	/*
125	 * If this arch/cpu has a short-circuited selection, don't loop through
126	 * all the possible functions, just test the best one
127	 */
128
129	fastest = NULL;
130
131#ifdef XOR_SELECT_TEMPLATE
132		fastest = XOR_SELECT_TEMPLATE(fastest);
133#endif
134
135#define xor_speed(templ)	do_xor_speed((templ), b1, b2)
136
137	if (fastest) {
138		printk(KERN_INFO "xor: automatically using best "
139				 "checksumming function:\n");
140		xor_speed(fastest);
141		goto out;
142	} else {
143		printk(KERN_INFO "xor: measuring software checksum speed\n");
144		XOR_TRY_TEMPLATES;
145		fastest = template_list;
146		for (f = fastest; f; f = f->next)
147			if (f->speed > fastest->speed)
148				fastest = f;
149	}
150
151	printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
152	       fastest->name, fastest->speed / 1000, fastest->speed % 1000);
153
154#undef xor_speed
155
156 out:
157	free_pages((unsigned long)b1, 2);
158
159	active_template = fastest;
160	return 0;
161}
162
163static __exit void xor_exit(void) { }
164
165MODULE_LICENSE("GPL");
166
167/* when built-in xor.o must initialize before drivers/md/md.o */
168core_initcall(calibrate_xor_blocks);
169module_exit(xor_exit);
170