Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame^] | 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 | } |