[linux.git] / kernel / time / test_udelay.c

// 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 struct dentry *udelay_test_debugfs_file;
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);
	udelay_test_debugfs_file = 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_remove(udelay_test_debugfs_file);
	mutex_unlock(&udelay_test_lock);
}

module_exit(udelay_test_exit);

MODULE_AUTHOR("David Riley <[email protected]>");
MODULE_LICENSE("GPL");
Commit	Line	Data
35728b82	1	// SPDX-License-Identifier: GPL-2.0
e704f93a DR	2	/*
	3	* udelay() test kernel module
	4	*
	5	* Test is executed by writing and reading to /sys/kernel/debug/udelay_test
	6	* Tests are configured by writing: USECS ITERATIONS
	7	* Tests are executed by reading from the same file.
	8	* Specifying usecs of 0 or negative values will run multiples tests.
	9	*
	10	* Copyright (C) 2014 Google, Inc.
e704f93a DR	11	*/
	12
	13	#include <linux/debugfs.h>
	14	#include <linux/delay.h>
	15	#include <linux/ktime.h>
	16	#include <linux/module.h>
	17	#include <linux/uaccess.h>
	18
	19	#define DEFAULT_ITERATIONS 100
	20
	21	#define DEBUGFS_FILENAME "udelay_test"
	22
	23	static DEFINE_MUTEX(udelay_test_lock);
	24	static struct dentry *udelay_test_debugfs_file;
	25	static int udelay_test_usecs;
	26	static int udelay_test_iterations = DEFAULT_ITERATIONS;
	27
	28	static int udelay_test_single(struct seq_file *s, int usecs, uint32_t iters)
	29	{
	30	int min = 0, max = 0, fail_count = 0;
	31	uint64_t sum = 0;
	32	uint64_t avg;
	33	int i;
	34	/* Allow udelay to be up to 0.5% fast */
	35	int allowed_error_ns = usecs * 5;
	36
	37	for (i = 0; i < iters; ++i) {
4a19bd3d	38	s64 kt1, kt2;
e704f93a DR	39	int time_passed;
e704f93a DR	40
4a19bd3d	41	kt1 = ktime_get_ns();
e704f93a	42	udelay(usecs);
4a19bd3d AB	43	kt2 = ktime_get_ns();
4a19bd3d AB	44	time_passed = kt2 - kt1;
e704f93a DR	45
	46	if (i == 0 \|\| time_passed < min)
	47	min = time_passed;
	48	if (i == 0 \|\| time_passed > max)
	49	max = time_passed;
	50	if ((time_passed + allowed_error_ns) / 1000 < usecs)
	51	++fail_count;
	52	WARN_ON(time_passed < 0);
	53	sum += time_passed;
	54	}
	55
	56	avg = sum;
	57	do_div(avg, iters);
	58	seq_printf(s, "%d usecs x %d: exp=%d allowed=%d min=%d avg=%lld max=%d",
	59	usecs, iters, usecs * 1000,
	60	(usecs * 1000) - allowed_error_ns, min, avg, max);
	61	if (fail_count)
	62	seq_printf(s, " FAIL=%d", fail_count);
	63	seq_puts(s, "\n");
	64
	65	return 0;
	66	}
	67
	68	static int udelay_test_show(struct seq_file s, void v)
	69	{
	70	int usecs;
	71	int iters;
	72	int ret = 0;
	73
	74	mutex_lock(&udelay_test_lock);
	75	usecs = udelay_test_usecs;
	76	iters = udelay_test_iterations;
	77	mutex_unlock(&udelay_test_lock);
	78
	79	if (usecs > 0 && iters > 0) {
	80	return udelay_test_single(s, usecs, iters);
	81	} else if (usecs == 0) {
4a19bd3d	82	struct timespec64 ts;
e704f93a	83
4a19bd3d AB	84	ktime_get_ts64(&ts);
	85	seq_printf(s, "udelay() test (lpj=%ld kt=%lld.%09ld)\n",
	86	loops_per_jiffy, (s64)ts.tv_sec, ts.tv_nsec);
e704f93a DR	87	seq_puts(s, "usage:\n");
	88	seq_puts(s, "echo USECS [ITERS] > " DEBUGFS_FILENAME "\n");
	89	seq_puts(s, "cat " DEBUGFS_FILENAME "\n");
	90	}
	91
	92	return ret;
	93	}
	94
	95	static int udelay_test_open(struct inode inode, struct file file)
	96	{
	97	return single_open(file, udelay_test_show, inode->i_private);
	98	}
	99
	100	static ssize_t udelay_test_write(struct file file, const char __user buf,
	101	size_t count, loff_t *pos)
	102	{
	103	char lbuf[32];
	104	int ret;
	105	int usecs;
	106	int iters;
	107
	108	if (count >= sizeof(lbuf))
	109	return -EINVAL;
	110
	111	if (copy_from_user(lbuf, buf, count))
	112	return -EFAULT;
	113	lbuf[count] = '\0';
	114
	115	ret = sscanf(lbuf, "%d %d", &usecs, &iters);
	116	if (ret < 1)
	117	return -EINVAL;
	118	else if (ret < 2)
	119	iters = DEFAULT_ITERATIONS;
	120
	121	mutex_lock(&udelay_test_lock);
	122	udelay_test_usecs = usecs;
	123	udelay_test_iterations = iters;
	124	mutex_unlock(&udelay_test_lock);
	125
	126	return count;
	127	}
	128
	129	static const struct file_operations udelay_test_debugfs_ops = {
	130	.owner = THIS_MODULE,
	131	.open = udelay_test_open,
	132	.read = seq_read,
	133	.write = udelay_test_write,
	134	.llseek = seq_lseek,
	135	.release = single_release,
	136	};
	137
	138	static int __init udelay_test_init(void)
	139	{
	140	mutex_lock(&udelay_test_lock);
	141	udelay_test_debugfs_file = debugfs_create_file(DEBUGFS_FILENAME,
	142	S_IRUSR, NULL, NULL, &udelay_test_debugfs_ops);
	143	mutex_unlock(&udelay_test_lock);
	144
	145	return 0;
	146	}
	147
	148	module_init(udelay_test_init);
	149
	150	static void __exit udelay_test_exit(void)
151	{
152	mutex_lock(&udelay_test_lock);
153	debugfs_remove(udelay_test_debugfs_file);
154	mutex_unlock(&udelay_test_lock);
155	}
156
157	module_exit(udelay_test_exit);
158
159	MODULE_AUTHOR("David Riley <[email protected]>");
160	MODULE_LICENSE("GPL");