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. */
24 static struct xor_block_template *active_template;
25
26 void
xor_blocks(unsigned int src_count,unsigned int bytes,void * dest,void ** srcs)27 xor_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 }
52 EXPORT_SYMBOL(xor_blocks);
53
54 /* Set of all registered templates. */
55 static struct xor_block_template *__initdata template_list;
56
57 #ifndef MODULE
do_xor_register(struct xor_block_template * tmpl)58 static void __init do_xor_register(struct xor_block_template *tmpl)
59 {
60 tmpl->next = template_list;
61 template_list = tmpl;
62 }
63
register_xor_blocks(void)64 static 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
82 static void __init
do_xor_speed(struct xor_block_template * tmpl,void * b1,void * b2)83 do_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
118 static int __init
calibrate_xor_blocks(void)119 calibrate_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);
161 out:
162 active_template = fastest;
163 return 0;
164 }
165
xor_exit(void)166 static __exit void xor_exit(void) { }
167
168 MODULE_LICENSE("GPL");
169
170 #ifndef MODULE
171 /* when built-in xor.o must initialize before drivers/md/md.o */
172 core_initcall(register_xor_blocks);
173 #endif
174
175 module_init(calibrate_xor_blocks);
176 module_exit(xor_exit);
177