1 /* 2 * Precise Delay Loops for S390 3 * 4 * Copyright IBM Corp. 1999, 2008 5 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>, 6 * Heiko Carstens <heiko.carstens@de.ibm.com>, 7 */ 8 9 #include <linux/sched.h> 10 #include <linux/delay.h> 11 #include <linux/timex.h> 12 #include <linux/module.h> 13 #include <linux/irqflags.h> 14 #include <linux/interrupt.h> 15 #include <asm/vtimer.h> 16 #include <asm/div64.h> 17 18 void __delay(unsigned long loops) 19 { 20 /* 21 * To end the bloody studid and useless discussion about the 22 * BogoMips number I took the liberty to define the __delay 23 * function in a way that that resulting BogoMips number will 24 * yield the megahertz number of the cpu. The important function 25 * is udelay and that is done using the tod clock. -- martin. 26 */ 27 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1)); 28 } 29 EXPORT_SYMBOL(__delay); 30 31 static void __udelay_disabled(unsigned long long usecs) 32 { 33 unsigned long cr0, cr6, new; 34 u64 clock_saved, end; 35 36 end = get_tod_clock() + (usecs << 12); 37 clock_saved = local_tick_disable(); 38 __ctl_store(cr0, 0, 0); 39 __ctl_store(cr6, 6, 6); 40 new = (cr0 & 0xffff00e0) | 0x00000800; 41 __ctl_load(new , 0, 0); 42 new = 0; 43 __ctl_load(new, 6, 6); 44 lockdep_off(); 45 do { 46 set_clock_comparator(end); 47 enabled_wait(); 48 } while (get_tod_clock_fast() < end); 49 lockdep_on(); 50 __ctl_load(cr0, 0, 0); 51 __ctl_load(cr6, 6, 6); 52 local_tick_enable(clock_saved); 53 } 54 55 static void __udelay_enabled(unsigned long long usecs) 56 { 57 u64 clock_saved, end; 58 59 end = get_tod_clock_fast() + (usecs << 12); 60 do { 61 clock_saved = 0; 62 if (end < S390_lowcore.clock_comparator) { 63 clock_saved = local_tick_disable(); 64 set_clock_comparator(end); 65 } 66 enabled_wait(); 67 if (clock_saved) 68 local_tick_enable(clock_saved); 69 } while (get_tod_clock_fast() < end); 70 } 71 72 /* 73 * Waits for 'usecs' microseconds using the TOD clock comparator. 74 */ 75 void __udelay(unsigned long long usecs) 76 { 77 unsigned long flags; 78 79 preempt_disable(); 80 local_irq_save(flags); 81 if (in_irq()) { 82 __udelay_disabled(usecs); 83 goto out; 84 } 85 if (in_softirq()) { 86 if (raw_irqs_disabled_flags(flags)) 87 __udelay_disabled(usecs); 88 else 89 __udelay_enabled(usecs); 90 goto out; 91 } 92 if (raw_irqs_disabled_flags(flags)) { 93 local_bh_disable(); 94 __udelay_disabled(usecs); 95 _local_bh_enable(); 96 goto out; 97 } 98 __udelay_enabled(usecs); 99 out: 100 local_irq_restore(flags); 101 preempt_enable(); 102 } 103 EXPORT_SYMBOL(__udelay); 104 105 /* 106 * Simple udelay variant. To be used on startup and reboot 107 * when the interrupt handler isn't working. 108 */ 109 void udelay_simple(unsigned long long usecs) 110 { 111 u64 end; 112 113 end = get_tod_clock_fast() + (usecs << 12); 114 while (get_tod_clock_fast() < end) 115 cpu_relax(); 116 } 117 118 void __ndelay(unsigned long long nsecs) 119 { 120 u64 end; 121 122 nsecs <<= 9; 123 do_div(nsecs, 125); 124 end = get_tod_clock_fast() + nsecs; 125 if (nsecs & ~0xfffUL) 126 __udelay(nsecs >> 12); 127 while (get_tod_clock_fast() < end) 128 barrier(); 129 } 130 EXPORT_SYMBOL(__ndelay); 131