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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 */
8
9#include <linux/processor.h>
10#include <linux/delay.h>
11#include <asm/div64.h>
12#include <asm/timex.h>
13
14void __delay(unsigned long loops)
15{
16 /*
17 * To end the bloody studid and useless discussion about the
18 * BogoMips number I took the liberty to define the __delay
19 * function in a way that that resulting BogoMips number will
20 * yield the megahertz number of the cpu. The important function
21 * is udelay and that is done using the tod clock. -- martin.
22 */
23 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
24}
25EXPORT_SYMBOL(__delay);
26
27static void delay_loop(unsigned long delta)
28{
29 unsigned long end;
30
31 end = get_tod_clock_monotonic() + delta;
32 while (!tod_after(get_tod_clock_monotonic(), end))
33 cpu_relax();
34}
35
36void __udelay(unsigned long usecs)
37{
38 delay_loop(usecs << 12);
39}
40EXPORT_SYMBOL(__udelay);
41
42void __ndelay(unsigned long nsecs)
43{
44 nsecs <<= 9;
45 do_div(nsecs, 125);
46 delay_loop(nsecs);
47}
48EXPORT_SYMBOL(__ndelay);