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44511ab344
There is no need to keep the dentry pointer around for the created debugfs file, as it is only needed when removing it from the system. When it is to be removed, ask debugfs itself for the pointer, to save on storage and make things a bit simpler. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210216155020.1012407-1-gregkh@linuxfoundation.org
159 lines
3.6 KiB
C
159 lines
3.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* udelay() test kernel module
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*
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* Test is executed by writing and reading to /sys/kernel/debug/udelay_test
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* Tests are configured by writing: USECS ITERATIONS
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* Tests are executed by reading from the same file.
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* Specifying usecs of 0 or negative values will run multiples tests.
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*
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* Copyright (C) 2014 Google, Inc.
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*/
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#include <linux/debugfs.h>
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#include <linux/delay.h>
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#include <linux/ktime.h>
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#include <linux/module.h>
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#include <linux/uaccess.h>
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#define DEFAULT_ITERATIONS 100
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#define DEBUGFS_FILENAME "udelay_test"
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static DEFINE_MUTEX(udelay_test_lock);
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static int udelay_test_usecs;
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static int udelay_test_iterations = DEFAULT_ITERATIONS;
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static int udelay_test_single(struct seq_file *s, int usecs, uint32_t iters)
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{
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int min = 0, max = 0, fail_count = 0;
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uint64_t sum = 0;
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uint64_t avg;
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int i;
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/* Allow udelay to be up to 0.5% fast */
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int allowed_error_ns = usecs * 5;
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for (i = 0; i < iters; ++i) {
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s64 kt1, kt2;
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int time_passed;
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kt1 = ktime_get_ns();
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udelay(usecs);
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kt2 = ktime_get_ns();
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time_passed = kt2 - kt1;
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if (i == 0 || time_passed < min)
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min = time_passed;
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if (i == 0 || time_passed > max)
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max = time_passed;
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if ((time_passed + allowed_error_ns) / 1000 < usecs)
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++fail_count;
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WARN_ON(time_passed < 0);
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sum += time_passed;
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}
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avg = sum;
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do_div(avg, iters);
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seq_printf(s, "%d usecs x %d: exp=%d allowed=%d min=%d avg=%lld max=%d",
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usecs, iters, usecs * 1000,
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(usecs * 1000) - allowed_error_ns, min, avg, max);
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if (fail_count)
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seq_printf(s, " FAIL=%d", fail_count);
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seq_puts(s, "\n");
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return 0;
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}
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static int udelay_test_show(struct seq_file *s, void *v)
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{
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int usecs;
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int iters;
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int ret = 0;
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mutex_lock(&udelay_test_lock);
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usecs = udelay_test_usecs;
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iters = udelay_test_iterations;
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mutex_unlock(&udelay_test_lock);
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if (usecs > 0 && iters > 0) {
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return udelay_test_single(s, usecs, iters);
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} else if (usecs == 0) {
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struct timespec64 ts;
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ktime_get_ts64(&ts);
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seq_printf(s, "udelay() test (lpj=%ld kt=%lld.%09ld)\n",
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loops_per_jiffy, (s64)ts.tv_sec, ts.tv_nsec);
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seq_puts(s, "usage:\n");
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seq_puts(s, "echo USECS [ITERS] > " DEBUGFS_FILENAME "\n");
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seq_puts(s, "cat " DEBUGFS_FILENAME "\n");
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}
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return ret;
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}
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static int udelay_test_open(struct inode *inode, struct file *file)
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{
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return single_open(file, udelay_test_show, inode->i_private);
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}
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static ssize_t udelay_test_write(struct file *file, const char __user *buf,
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size_t count, loff_t *pos)
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{
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char lbuf[32];
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int ret;
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int usecs;
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int iters;
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if (count >= sizeof(lbuf))
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return -EINVAL;
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if (copy_from_user(lbuf, buf, count))
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return -EFAULT;
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lbuf[count] = '\0';
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ret = sscanf(lbuf, "%d %d", &usecs, &iters);
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if (ret < 1)
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return -EINVAL;
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else if (ret < 2)
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iters = DEFAULT_ITERATIONS;
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mutex_lock(&udelay_test_lock);
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udelay_test_usecs = usecs;
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udelay_test_iterations = iters;
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mutex_unlock(&udelay_test_lock);
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return count;
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}
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static const struct file_operations udelay_test_debugfs_ops = {
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.owner = THIS_MODULE,
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.open = udelay_test_open,
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.read = seq_read,
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.write = udelay_test_write,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static int __init udelay_test_init(void)
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{
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mutex_lock(&udelay_test_lock);
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debugfs_create_file(DEBUGFS_FILENAME, S_IRUSR, NULL, NULL,
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&udelay_test_debugfs_ops);
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mutex_unlock(&udelay_test_lock);
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return 0;
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}
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module_init(udelay_test_init);
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static void __exit udelay_test_exit(void)
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{
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mutex_lock(&udelay_test_lock);
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debugfs_remove(debugfs_lookup(DEBUGFS_FILENAME, NULL));
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mutex_unlock(&udelay_test_lock);
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}
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module_exit(udelay_test_exit);
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MODULE_AUTHOR("David Riley <davidriley@chromium.org>");
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MODULE_LICENSE("GPL");
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