1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * xor.c : Multiple Devices driver for Linux
4 *
5 * Copyright (C) 1996, 1997, 1998, 1999, 2000,
6 * Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.
7 *
8 * Dispatch optimized RAID-5 checksumming functions.
9 */
10
11#define BH_TRACE 0
12#include <linux/module.h>
13#include <linux/gfp.h>
14#include <linux/raid/xor.h>
15#include <linux/jiffies.h>
16#include <linux/preempt.h>
17#include <asm/xor.h>
18
19#ifndef XOR_SELECT_TEMPLATE
20#define XOR_SELECT_TEMPLATE(x) (x)
21#endif
22
23/* The xor routines to use.  */
24static struct xor_block_template *active_template;
25
26void
27xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
28{
29	unsigned long *p1, *p2, *p3, *p4;
30
31	p1 = (unsigned long *) srcs[0];
32	if (src_count == 1) {
33		active_template->do_2(bytes, dest, p1);
34		return;
35	}
36
37	p2 = (unsigned long *) srcs[1];
38	if (src_count == 2) {
39		active_template->do_3(bytes, dest, p1, p2);
40		return;
41	}
42
43	p3 = (unsigned long *) srcs[2];
44	if (src_count == 3) {
45		active_template->do_4(bytes, dest, p1, p2, p3);
46		return;
47	}
48
49	p4 = (unsigned long *) srcs[3];
50	active_template->do_5(bytes, dest, p1, p2, p3, p4);
51}
52EXPORT_SYMBOL(xor_blocks);
53
54/* Set of all registered templates.  */
55static struct xor_block_template *__initdata template_list;
56
57#ifndef MODULE
58static void __init do_xor_register(struct xor_block_template *tmpl)
59{
60	tmpl->next = template_list;
61	template_list = tmpl;
62}
63
64static int __init register_xor_blocks(void)
65{
66	active_template = XOR_SELECT_TEMPLATE(NULL);
67
68	if (!active_template) {
69#define xor_speed	do_xor_register
70		// register all the templates and pick the first as the default
71		XOR_TRY_TEMPLATES;
72#undef xor_speed
73		active_template = template_list;
74	}
75	return 0;
76}
77#endif
78
79#define BENCH_SIZE	4096
80#define REPS		800U
81
82static void __init
83do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
84{
85	int speed;
86	int i, j;
87	ktime_t min, start, diff;
88
89	tmpl->next = template_list;
90	template_list = tmpl;
91
92	preempt_disable();
93
94	min = (ktime_t)S64_MAX;
95	for (i = 0; i < 3; i++) {
96		start = ktime_get();
97		for (j = 0; j < REPS; j++) {
98			mb(); /* prevent loop optimization */
99			tmpl->do_2(BENCH_SIZE, b1, b2);
100			mb();
101		}
102		diff = ktime_sub(ktime_get(), start);
103		if (diff < min)
104			min = diff;
105	}
106
107	preempt_enable();
108
109	// bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]
110	if (!min)
111		min = 1;
112	speed = (1000 * REPS * BENCH_SIZE) / (unsigned int)ktime_to_ns(min);
113	tmpl->speed = speed;
114
115	pr_info("   %-16s: %5d MB/sec\n", tmpl->name, speed);
116}
117
118static int __init
119calibrate_xor_blocks(void)
120{
121	void *b1, *b2;
122	struct xor_block_template *f, *fastest;
123
124	fastest = XOR_SELECT_TEMPLATE(NULL);
125
126	if (fastest) {
127		printk(KERN_INFO "xor: automatically using best "
128				 "checksumming function   %-10s\n",
129		       fastest->name);
130		goto out;
131	}
132
133	b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
134	if (!b1) {
135		printk(KERN_WARNING "xor: Yikes!  No memory available.\n");
136		return -ENOMEM;
137	}
138	b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
139
140	/*
141	 * If this arch/cpu has a short-circuited selection, don't loop through
142	 * all the possible functions, just test the best one
143	 */
144
145#define xor_speed(templ)	do_xor_speed((templ), b1, b2)
146
147	printk(KERN_INFO "xor: measuring software checksum speed\n");
148	template_list = NULL;
149	XOR_TRY_TEMPLATES;
150	fastest = template_list;
151	for (f = fastest; f; f = f->next)
152		if (f->speed > fastest->speed)
153			fastest = f;
154
155	pr_info("xor: using function: %s (%d MB/sec)\n",
156	       fastest->name, fastest->speed);
157
158#undef xor_speed
159
160	free_pages((unsigned long)b1, 2);
161out:
162	active_template = fastest;
163	return 0;
164}
165
166static __exit void xor_exit(void) { }
167
168MODULE_LICENSE("GPL");
169
170#ifndef MODULE
171/* when built-in xor.o must initialize before drivers/md/md.o */
172core_initcall(register_xor_blocks);
173#endif
174
175module_init(calibrate_xor_blocks);
176module_exit(xor_exit);
177