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e704f93a DR |
1 | /* |
2 | * udelay() test kernel module | |
3 | * | |
4 | * Test is executed by writing and reading to /sys/kernel/debug/udelay_test | |
5 | * Tests are configured by writing: USECS ITERATIONS | |
6 | * Tests are executed by reading from the same file. | |
7 | * Specifying usecs of 0 or negative values will run multiples tests. | |
8 | * | |
9 | * Copyright (C) 2014 Google, Inc. | |
10 | * | |
11 | * This software is licensed under the terms of the GNU General Public | |
12 | * License version 2, as published by the Free Software Foundation, and | |
13 | * may be copied, distributed, and modified under those terms. | |
14 | * | |
15 | * This program is distributed in the hope that it will be useful, | |
16 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
18 | * GNU General Public License for more details. | |
19 | */ | |
20 | ||
21 | #include <linux/debugfs.h> | |
22 | #include <linux/delay.h> | |
23 | #include <linux/ktime.h> | |
24 | #include <linux/module.h> | |
25 | #include <linux/uaccess.h> | |
26 | ||
27 | #define DEFAULT_ITERATIONS 100 | |
28 | ||
29 | #define DEBUGFS_FILENAME "udelay_test" | |
30 | ||
31 | static DEFINE_MUTEX(udelay_test_lock); | |
32 | static struct dentry *udelay_test_debugfs_file; | |
33 | static int udelay_test_usecs; | |
34 | static int udelay_test_iterations = DEFAULT_ITERATIONS; | |
35 | ||
36 | static int udelay_test_single(struct seq_file *s, int usecs, uint32_t iters) | |
37 | { | |
38 | int min = 0, max = 0, fail_count = 0; | |
39 | uint64_t sum = 0; | |
40 | uint64_t avg; | |
41 | int i; | |
42 | /* Allow udelay to be up to 0.5% fast */ | |
43 | int allowed_error_ns = usecs * 5; | |
44 | ||
45 | for (i = 0; i < iters; ++i) { | |
46 | struct timespec ts1, ts2; | |
47 | int time_passed; | |
48 | ||
49 | ktime_get_ts(&ts1); | |
50 | udelay(usecs); | |
51 | ktime_get_ts(&ts2); | |
52 | time_passed = timespec_to_ns(&ts2) - timespec_to_ns(&ts1); | |
53 | ||
54 | if (i == 0 || time_passed < min) | |
55 | min = time_passed; | |
56 | if (i == 0 || time_passed > max) | |
57 | max = time_passed; | |
58 | if ((time_passed + allowed_error_ns) / 1000 < usecs) | |
59 | ++fail_count; | |
60 | WARN_ON(time_passed < 0); | |
61 | sum += time_passed; | |
62 | } | |
63 | ||
64 | avg = sum; | |
65 | do_div(avg, iters); | |
66 | seq_printf(s, "%d usecs x %d: exp=%d allowed=%d min=%d avg=%lld max=%d", | |
67 | usecs, iters, usecs * 1000, | |
68 | (usecs * 1000) - allowed_error_ns, min, avg, max); | |
69 | if (fail_count) | |
70 | seq_printf(s, " FAIL=%d", fail_count); | |
71 | seq_puts(s, "\n"); | |
72 | ||
73 | return 0; | |
74 | } | |
75 | ||
76 | static int udelay_test_show(struct seq_file *s, void *v) | |
77 | { | |
78 | int usecs; | |
79 | int iters; | |
80 | int ret = 0; | |
81 | ||
82 | mutex_lock(&udelay_test_lock); | |
83 | usecs = udelay_test_usecs; | |
84 | iters = udelay_test_iterations; | |
85 | mutex_unlock(&udelay_test_lock); | |
86 | ||
87 | if (usecs > 0 && iters > 0) { | |
88 | return udelay_test_single(s, usecs, iters); | |
89 | } else if (usecs == 0) { | |
90 | struct timespec ts; | |
91 | ||
92 | ktime_get_ts(&ts); | |
93 | seq_printf(s, "udelay() test (lpj=%ld kt=%ld.%09ld)\n", | |
94 | loops_per_jiffy, ts.tv_sec, ts.tv_nsec); | |
95 | seq_puts(s, "usage:\n"); | |
96 | seq_puts(s, "echo USECS [ITERS] > " DEBUGFS_FILENAME "\n"); | |
97 | seq_puts(s, "cat " DEBUGFS_FILENAME "\n"); | |
98 | } | |
99 | ||
100 | return ret; | |
101 | } | |
102 | ||
103 | static int udelay_test_open(struct inode *inode, struct file *file) | |
104 | { | |
105 | return single_open(file, udelay_test_show, inode->i_private); | |
106 | } | |
107 | ||
108 | static ssize_t udelay_test_write(struct file *file, const char __user *buf, | |
109 | size_t count, loff_t *pos) | |
110 | { | |
111 | char lbuf[32]; | |
112 | int ret; | |
113 | int usecs; | |
114 | int iters; | |
115 | ||
116 | if (count >= sizeof(lbuf)) | |
117 | return -EINVAL; | |
118 | ||
119 | if (copy_from_user(lbuf, buf, count)) | |
120 | return -EFAULT; | |
121 | lbuf[count] = '\0'; | |
122 | ||
123 | ret = sscanf(lbuf, "%d %d", &usecs, &iters); | |
124 | if (ret < 1) | |
125 | return -EINVAL; | |
126 | else if (ret < 2) | |
127 | iters = DEFAULT_ITERATIONS; | |
128 | ||
129 | mutex_lock(&udelay_test_lock); | |
130 | udelay_test_usecs = usecs; | |
131 | udelay_test_iterations = iters; | |
132 | mutex_unlock(&udelay_test_lock); | |
133 | ||
134 | return count; | |
135 | } | |
136 | ||
137 | static const struct file_operations udelay_test_debugfs_ops = { | |
138 | .owner = THIS_MODULE, | |
139 | .open = udelay_test_open, | |
140 | .read = seq_read, | |
141 | .write = udelay_test_write, | |
142 | .llseek = seq_lseek, | |
143 | .release = single_release, | |
144 | }; | |
145 | ||
146 | static int __init udelay_test_init(void) | |
147 | { | |
148 | mutex_lock(&udelay_test_lock); | |
149 | udelay_test_debugfs_file = debugfs_create_file(DEBUGFS_FILENAME, | |
150 | S_IRUSR, NULL, NULL, &udelay_test_debugfs_ops); | |
151 | mutex_unlock(&udelay_test_lock); | |
152 | ||
153 | return 0; | |
154 | } | |
155 | ||
156 | module_init(udelay_test_init); | |
157 | ||
158 | static void __exit udelay_test_exit(void) | |
159 | { | |
160 | mutex_lock(&udelay_test_lock); | |
161 | debugfs_remove(udelay_test_debugfs_file); | |
162 | mutex_unlock(&udelay_test_lock); | |
163 | } | |
164 | ||
165 | module_exit(udelay_test_exit); | |
166 | ||
167 | MODULE_AUTHOR("David Riley <davidriley@chromium.org>"); | |
168 | MODULE_LICENSE("GPL"); |