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linux/kernel/time/test_udelay.c
Arnd Bergmann 4a19bd3d22 time: Avoid timespec in udelay_test
udelay_test_single() uses ktime_get_ts() to get two timespec values
and calculate the difference between them, while udelay_test_show()
uses the same to printk() the current monotonic time.

Both of these are y2038 safe on all machines, but we want to
get rid of struct timespec anyway, so this converts the code to
use ktime_get_ns() and ktime_get_ts64() respectively.

Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-06-20 12:47:26 -07:00

169 lines
4.1 KiB
C

/*
* 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.
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#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 <davidriley@chromium.org>");
MODULE_LICENSE("GPL");