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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 * Heiko Carstens <heiko.carstens@de.ibm.com>,
8 */
9
10#include <linux/processor.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 * To end the bloody studid and useless discussion about the
19 * BogoMips number I took the liberty to define the __delay
20 * function in a way that that resulting BogoMips number will
21 * yield the megahertz number of the cpu. The important function
22 * is udelay and that is done using the tod clock. -- martin.
23 */
24 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
25}
26EXPORT_SYMBOL(__delay);
27
28static void delay_loop(unsigned long delta)
29{
30 unsigned long end;
31
32 end = get_tod_clock_monotonic() + delta;
33 while (!tod_after(get_tod_clock_monotonic(), end))
34 cpu_relax();
35}
36
37void __udelay(unsigned long usecs)
38{
39 delay_loop(usecs << 12);
40}
41EXPORT_SYMBOL(__udelay);
42
43void __ndelay(unsigned long nsecs)
44{
45 nsecs <<= 9;
46 do_div(nsecs, 125);
47 delay_loop(nsecs);
48}
49EXPORT_SYMBOL(__ndelay);