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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161// 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_DESCRIPTION("udelay test module");MODULE_AUTHOR("David Riley <davidriley@chromium.org>");MODULE_LICENSE("GPL");