delay.c

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 *    Precise Delay Loops for S390
 4 *
 5 *    Copyright IBM Corp. 1999, 2008
 6 *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
 7 */
 8
 9#include <linux/processor.h>
10#include <linux/export.h>
11#include <linux/delay.h>
12#include <asm/div64.h>
13#include <asm/timex.h>
14
15void __delay(unsigned long loops)
16{
17	/*
18	 * Loop 'loops' times. Callers must not assume a specific
19	 * amount of time passes before this function returns.
20	 */
21	asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
22}
23EXPORT_SYMBOL(__delay);
24
25static void delay_loop(unsigned long delta)
26{
27	unsigned long end;
28
29	end = get_tod_clock_monotonic() + delta;
30	while (!tod_after(get_tod_clock_monotonic(), end))
31		cpu_relax();
32}
33
34void __udelay(unsigned long usecs)
35{
36	delay_loop(usecs << 12);
37}
38EXPORT_SYMBOL(__udelay);
39
40void __ndelay(unsigned long nsecs)
41{
42	nsecs <<= 9;
43	do_div(nsecs, 125);
44	delay_loop(nsecs);
45}
46EXPORT_SYMBOL(__ndelay);