1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Precise Delay Loops for S390 4 * 5 * Copyright IBM Corp. 1999, 2008 6 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>, 7 * Heiko Carstens <heiko.carstens@de.ibm.com>, 8 */ 9 10 #include <linux/sched.h> 11 #include <linux/delay.h> 12 #include <linux/timex.h> 13 #include <linux/export.h> 14 #include <linux/irqflags.h> 15 #include <linux/interrupt.h> 16 #include <linux/irq.h> 17 #include <asm/vtimer.h> 18 #include <asm/div64.h> 19 #include <asm/idle.h> 20 21 void __delay(unsigned long loops) 22 { 23 /* 24 * To end the bloody studid and useless discussion about the 25 * BogoMips number I took the liberty to define the __delay 26 * function in a way that that resulting BogoMips number will 27 * yield the megahertz number of the cpu. The important function 28 * is udelay and that is done using the tod clock. -- martin. 29 */ 30 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1)); 31 } 32 EXPORT_SYMBOL(__delay); 33 34 static void __udelay_disabled(unsigned long long usecs) 35 { 36 unsigned long cr0, cr0_new, psw_mask; 37 struct s390_idle_data idle; 38 u64 end; 39 40 end = get_tod_clock() + (usecs << 12); 41 __ctl_store(cr0, 0, 0); 42 cr0_new = cr0 & ~CR0_IRQ_SUBCLASS_MASK; 43 cr0_new |= (1UL << (63 - 52)); /* enable clock comparator irq */ 44 __ctl_load(cr0_new, 0, 0); 45 psw_mask = __extract_psw() | PSW_MASK_EXT | PSW_MASK_WAIT; 46 set_clock_comparator(end); 47 set_cpu_flag(CIF_IGNORE_IRQ); 48 psw_idle(&idle, psw_mask); 49 trace_hardirqs_off(); 50 clear_cpu_flag(CIF_IGNORE_IRQ); 51 set_clock_comparator(S390_lowcore.clock_comparator); 52 __ctl_load(cr0, 0, 0); 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 (tod_after(S390_lowcore.clock_comparator, end)) { 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