1 /* 2 * arch/s390/lib/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/sched.h> 15 #include <linux/delay.h> 16 #include <linux/timex.h> 17 #include <linux/irqflags.h> 18 19 void __delay(unsigned long loops) 20 { 21 /* 22 * To end the bloody studid and useless discussion about the 23 * BogoMips number I took the liberty to define the __delay 24 * function in a way that that resulting BogoMips number will 25 * yield the megahertz number of the cpu. The important function 26 * is udelay and that is done using the tod clock. -- martin. 27 */ 28 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1)); 29 } 30 31 /* 32 * Waits for 'usecs' microseconds using the TOD clock comparator. 33 */ 34 void __udelay(unsigned long usecs) 35 { 36 u64 end, time, jiffy_timer = 0; 37 unsigned long flags, cr0, mask, dummy; 38 39 local_irq_save(flags); 40 if (raw_irqs_disabled_flags(flags)) { 41 jiffy_timer = S390_lowcore.jiffy_timer; 42 S390_lowcore.jiffy_timer = -1ULL - (4096 << 12); 43 __ctl_store(cr0, 0, 0); 44 dummy = (cr0 & 0xffff00e0) | 0x00000800; 45 __ctl_load(dummy , 0, 0); 46 mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT; 47 } else 48 mask = psw_kernel_bits | PSW_MASK_WAIT | 49 PSW_MASK_EXT | PSW_MASK_IO; 50 51 end = get_clock() + ((u64) usecs << 12); 52 do { 53 time = end < S390_lowcore.jiffy_timer ? 54 end : S390_lowcore.jiffy_timer; 55 set_clock_comparator(time); 56 trace_hardirqs_on(); 57 __load_psw_mask(mask); 58 local_irq_disable(); 59 } while (get_clock() < end); 60 61 if (raw_irqs_disabled_flags(flags)) { 62 __ctl_load(cr0, 0, 0); 63 S390_lowcore.jiffy_timer = jiffy_timer; 64 } 65 set_clock_comparator(S390_lowcore.jiffy_timer); 66 local_irq_restore(flags); 67 } 68