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/export.h> 13 #include <linux/irqflags.h> 14 #include <linux/interrupt.h> 15 #include <linux/irq.h> 16 #include <asm/vtimer.h> 17 #include <asm/div64.h> 18 #include <asm/idle.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 EXPORT_SYMBOL(__delay); 32 33 static void __udelay_disabled(unsigned long long usecs) 34 { 35 unsigned long cr0, cr0_new, psw_mask; 36 struct s390_idle_data idle; 37 u64 end; 38 39 end = get_tod_clock() + (usecs << 12); 40 __ctl_store(cr0, 0, 0); 41 cr0_new = cr0 & ~CR0_IRQ_SUBCLASS_MASK; 42 cr0_new |= (1UL << (63 - 52)); /* enable clock comparator irq */ 43 __ctl_load(cr0_new, 0, 0); 44 psw_mask = __extract_psw() | PSW_MASK_EXT | PSW_MASK_WAIT; 45 set_clock_comparator(end); 46 set_cpu_flag(CIF_IGNORE_IRQ); 47 psw_idle(&idle, psw_mask); 48 clear_cpu_flag(CIF_IGNORE_IRQ); 49 set_clock_comparator(S390_lowcore.clock_comparator); 50 __ctl_load(cr0, 0, 0); 51 } 52 53 static void __udelay_enabled(unsigned long long usecs) 54 { 55 u64 clock_saved, end; 56 57 end = get_tod_clock_fast() + (usecs << 12); 58 do { 59 clock_saved = 0; 60 if (end < S390_lowcore.clock_comparator) { 61 clock_saved = local_tick_disable(); 62 set_clock_comparator(end); 63 } 64 enabled_wait(); 65 if (clock_saved) 66 local_tick_enable(clock_saved); 67 } while (get_tod_clock_fast() < end); 68 } 69 70 /* 71 * Waits for 'usecs' microseconds using the TOD clock comparator. 72 */ 73 void __udelay(unsigned long long usecs) 74 { 75 unsigned long flags; 76 77 preempt_disable(); 78 local_irq_save(flags); 79 if (in_irq()) { 80 __udelay_disabled(usecs); 81 goto out; 82 } 83 if (in_softirq()) { 84 if (raw_irqs_disabled_flags(flags)) 85 __udelay_disabled(usecs); 86 else 87 __udelay_enabled(usecs); 88 goto out; 89 } 90 if (raw_irqs_disabled_flags(flags)) { 91 local_bh_disable(); 92 __udelay_disabled(usecs); 93 _local_bh_enable(); 94 goto out; 95 } 96 __udelay_enabled(usecs); 97 out: 98 local_irq_restore(flags); 99 preempt_enable(); 100 } 101 EXPORT_SYMBOL(__udelay); 102 103 /* 104 * Simple udelay variant. To be used on startup and reboot 105 * when the interrupt handler isn't working. 106 */ 107 void udelay_simple(unsigned long long usecs) 108 { 109 u64 end; 110 111 end = get_tod_clock_fast() + (usecs << 12); 112 while (get_tod_clock_fast() < end) 113 cpu_relax(); 114 } 115 116 void __ndelay(unsigned long long nsecs) 117 { 118 u64 end; 119 120 nsecs <<= 9; 121 do_div(nsecs, 125); 122 end = get_tod_clock_fast() + nsecs; 123 if (nsecs & ~0xfffUL) 124 __udelay(nsecs >> 12); 125 while (get_tod_clock_fast() < end) 126 barrier(); 127 } 128 EXPORT_SYMBOL(__ndelay); 129