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 #include <linux/interrupt.h> 19 20 void __delay(unsigned long loops) 21 { 22 /* 23 * To end the bloody studid and useless discussion about the 24 * BogoMips number I took the liberty to define the __delay 25 * function in a way that that resulting BogoMips number will 26 * yield the megahertz number of the cpu. The important function 27 * is udelay and that is done using the tod clock. -- martin. 28 */ 29 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1)); 30 } 31 32 /* 33 * Waits for 'usecs' microseconds using the TOD clock comparator. 34 */ 35 void __udelay(unsigned long usecs) 36 { 37 u64 end, time, old_cc = 0; 38 unsigned long flags, cr0, mask, dummy; 39 int irq_context; 40 41 irq_context = in_interrupt(); 42 if (!irq_context) 43 local_bh_disable(); 44 local_irq_save(flags); 45 if (raw_irqs_disabled_flags(flags)) { 46 old_cc = S390_lowcore.clock_comparator; 47 S390_lowcore.clock_comparator = -1ULL; 48 __ctl_store(cr0, 0, 0); 49 dummy = (cr0 & 0xffff00e0) | 0x00000800; 50 __ctl_load(dummy , 0, 0); 51 mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT; 52 } else 53 mask = psw_kernel_bits | PSW_MASK_WAIT | 54 PSW_MASK_EXT | PSW_MASK_IO; 55 56 end = get_clock() + ((u64) usecs << 12); 57 do { 58 time = end < S390_lowcore.clock_comparator ? 59 end : S390_lowcore.clock_comparator; 60 set_clock_comparator(time); 61 trace_hardirqs_on(); 62 __load_psw_mask(mask); 63 local_irq_disable(); 64 } while (get_clock() < end); 65 66 if (raw_irqs_disabled_flags(flags)) { 67 __ctl_load(cr0, 0, 0); 68 S390_lowcore.clock_comparator = old_cc; 69 } 70 if (!irq_context) 71 _local_bh_enable(); 72 set_clock_comparator(S390_lowcore.clock_comparator); 73 local_irq_restore(flags); 74 } 75