Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
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 | ||
22 | void __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 | */ | |
40 | void __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 | } |