blob: e96c35bddac778030a7de4c184e4d781248a0fe4 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * arch/s390/kernel/delay.c
3 * Precise Delay Loops for S390
4 *
5 * S390 version
6 * Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
7 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
8 *
9 * Derived from "arch/i386/lib/delay.c"
10 * Copyright (C) 1993 Linus Torvalds
11 * Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
12 */
13
14#include <linux/config.h>
15#include <linux/sched.h>
16#include <linux/delay.h>
17
18#ifdef CONFIG_SMP
19#include <asm/smp.h>
20#endif
21
22void __delay(unsigned long loops)
23{
24 /*
25 * To end the bloody studid and useless discussion about the
26 * BogoMips number I took the liberty to define the __delay
27 * function in a way that that resulting BogoMips number will
28 * yield the megahertz number of the cpu. The important function
29 * is udelay and that is done using the tod clock. -- martin.
30 */
31 __asm__ __volatile__(
32 "0: brct %0,0b"
33 : /* no outputs */ : "r" (loops/2) );
34}
35
36/*
37 * Waits for 'usecs' microseconds using the tod clock, giving up the time slice
38 * of the virtual PU inbetween to avoid congestion.
39 */
40void __udelay(unsigned long usecs)
41{
42 uint64_t start_cc, end_cc;
43
44 if (usecs == 0)
45 return;
46 asm volatile ("STCK %0" : "=m" (start_cc));
47 do {
48 cpu_relax();
49 asm volatile ("STCK %0" : "=m" (end_cc));
50 } while (((end_cc - start_cc)/4096) < usecs);
51}