intel_display_jiffies.h

 1/* SPDX-License-Identifier: MIT */
 2/* Copyright © 2025 Intel Corporation */
 3
 4#ifndef __INTEL_DISPLAY_JIFFIES_H__
 5#define __INTEL_DISPLAY_JIFFIES_H__
 6
 7#include <linux/jiffies.h>
 8
 9static inline unsigned long msecs_to_jiffies_timeout(const unsigned int m)
10{
11	unsigned long j = msecs_to_jiffies(m);
12
13	return min_t(unsigned long, MAX_JIFFY_OFFSET, j + 1);
14}
15
16/*
17 * If you need to wait X milliseconds between events A and B, but event B
18 * doesn't happen exactly after event A, you record the timestamp (jiffies) of
19 * when event A happened, then just before event B you call this function and
20 * pass the timestamp as the first argument, and X as the second argument.
21 */
22static inline void
23wait_remaining_ms_from_jiffies(unsigned long timestamp_jiffies, int to_wait_ms)
24{
25	unsigned long target_jiffies, tmp_jiffies, remaining_jiffies;
26
27	/*
28	 * Don't re-read the value of "jiffies" every time since it may change
29	 * behind our back and break the math.
30	 */
31	tmp_jiffies = jiffies;
32	target_jiffies = timestamp_jiffies +
33			 msecs_to_jiffies_timeout(to_wait_ms);
34
35	if (time_after(target_jiffies, tmp_jiffies)) {
36		remaining_jiffies = target_jiffies - tmp_jiffies;
37		while (remaining_jiffies)
38			remaining_jiffies =
39			    schedule_timeout_uninterruptible(remaining_jiffies);
40	}
41}
42
43#endif /* __INTEL_DISPLAY_JIFFIES_H__ */