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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 | // SPDX-License-Identifier: GPL-2.0 /* * udelay() test kernel module * * Test is executed by writing and reading to /sys/kernel/debug/udelay_test * Tests are configured by writing: USECS ITERATIONS * Tests are executed by reading from the same file. * Specifying usecs of 0 or negative values will run multiples tests. * * Copyright (C) 2014 Google, Inc. */ #include <linux/debugfs.h> #include <linux/delay.h> #include <linux/ktime.h> #include <linux/module.h> #include <linux/uaccess.h> #define DEFAULT_ITERATIONS 100 #define DEBUGFS_FILENAME "udelay_test" static DEFINE_MUTEX(udelay_test_lock); static int udelay_test_usecs; static int udelay_test_iterations = DEFAULT_ITERATIONS; static int udelay_test_single(struct seq_file *s, int usecs, uint32_t iters) { int min = 0, max = 0, fail_count = 0; uint64_t sum = 0; uint64_t avg; int i; /* Allow udelay to be up to 0.5% fast */ int allowed_error_ns = usecs * 5; for (i = 0; i < iters; ++i) { s64 kt1, kt2; int time_passed; kt1 = ktime_get_ns(); udelay(usecs); kt2 = ktime_get_ns(); time_passed = kt2 - kt1; if (i == 0 || time_passed < min) min = time_passed; if (i == 0 || time_passed > max) max = time_passed; if ((time_passed + allowed_error_ns) / 1000 < usecs) ++fail_count; WARN_ON(time_passed < 0); sum += time_passed; } avg = sum; do_div(avg, iters); seq_printf(s, "%d usecs x %d: exp=%d allowed=%d min=%d avg=%lld max=%d", usecs, iters, usecs * 1000, (usecs * 1000) - allowed_error_ns, min, avg, max); if (fail_count) seq_printf(s, " FAIL=%d", fail_count); seq_puts(s, "\n"); return 0; } static int udelay_test_show(struct seq_file *s, void *v) { int usecs; int iters; int ret = 0; mutex_lock(&udelay_test_lock); usecs = udelay_test_usecs; iters = udelay_test_iterations; mutex_unlock(&udelay_test_lock); if (usecs > 0 && iters > 0) { return udelay_test_single(s, usecs, iters); } else if (usecs == 0) { struct timespec64 ts; ktime_get_ts64(&ts); seq_printf(s, "udelay() test (lpj=%ld kt=%lld.%09ld)\n", loops_per_jiffy, (s64)ts.tv_sec, ts.tv_nsec); seq_puts(s, "usage:\n"); seq_puts(s, "echo USECS [ITERS] > " DEBUGFS_FILENAME "\n"); seq_puts(s, "cat " DEBUGFS_FILENAME "\n"); } return ret; } static int udelay_test_open(struct inode *inode, struct file *file) { return single_open(file, udelay_test_show, inode->i_private); } static ssize_t udelay_test_write(struct file *file, const char __user *buf, size_t count, loff_t *pos) { char lbuf[32]; int ret; int usecs; int iters; if (count >= sizeof(lbuf)) return -EINVAL; if (copy_from_user(lbuf, buf, count)) return -EFAULT; lbuf[count] = '\0'; ret = sscanf(lbuf, "%d %d", &usecs, &iters); if (ret < 1) return -EINVAL; else if (ret < 2) iters = DEFAULT_ITERATIONS; mutex_lock(&udelay_test_lock); udelay_test_usecs = usecs; udelay_test_iterations = iters; mutex_unlock(&udelay_test_lock); return count; } static const struct file_operations udelay_test_debugfs_ops = { .owner = THIS_MODULE, .open = udelay_test_open, .read = seq_read, .write = udelay_test_write, .llseek = seq_lseek, .release = single_release, }; static int __init udelay_test_init(void) { mutex_lock(&udelay_test_lock); debugfs_create_file(DEBUGFS_FILENAME, S_IRUSR, NULL, NULL, &udelay_test_debugfs_ops); mutex_unlock(&udelay_test_lock); return 0; } module_init(udelay_test_init); static void __exit udelay_test_exit(void) { mutex_lock(&udelay_test_lock); debugfs_lookup_and_remove(DEBUGFS_FILENAME, NULL); mutex_unlock(&udelay_test_lock); } module_exit(udelay_test_exit); MODULE_AUTHOR("David Riley <davidriley@chromium.org>"); MODULE_LICENSE("GPL"); |