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, flags; 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 local_irq_save(flags); 49 psw_idle(&idle, psw_mask); 50 local_irq_restore(flags); 51 clear_cpu_flag(CIF_IGNORE_IRQ); 52 set_clock_comparator(S390_lowcore.clock_comparator); 53 __ctl_load(cr0, 0, 0); 54 } 55 56 static void __udelay_enabled(unsigned long long usecs) 57 { 58 u64 clock_saved, end; 59 60 end = get_tod_clock_fast() + (usecs << 12); 61 do { 62 clock_saved = 0; 63 if (tod_after(S390_lowcore.clock_comparator, end)) { 64 clock_saved = local_tick_disable(); 65 set_clock_comparator(end); 66 } 67 enabled_wait(); 68 if (clock_saved) 69 local_tick_enable(clock_saved); 70 } while (get_tod_clock_fast() < end); 71 } 72 73 /* 74 * Waits for 'usecs' microseconds using the TOD clock comparator. 75 */ 76 void __udelay(unsigned long long usecs) 77 { 78 unsigned long flags; 79 80 preempt_disable(); 81 local_irq_save(flags); 82 if (in_irq()) { 83 __udelay_disabled(usecs); 84 goto out; 85 } 86 if (in_softirq()) { 87 if (raw_irqs_disabled_flags(flags)) 88 __udelay_disabled(usecs); 89 else 90 __udelay_enabled(usecs); 91 goto out; 92 } 93 if (raw_irqs_disabled_flags(flags)) { 94 local_bh_disable(); 95 __udelay_disabled(usecs); 96 _local_bh_enable(); 97 goto out; 98 } 99 __udelay_enabled(usecs); 100 out: 101 local_irq_restore(flags); 102 preempt_enable(); 103 } 104 EXPORT_SYMBOL(__udelay); 105 106 /* 107 * Simple udelay variant. To be used on startup and reboot 108 * when the interrupt handler isn't working. 109 */ 110 void udelay_simple(unsigned long long usecs) 111 { 112 u64 end; 113 114 end = get_tod_clock_fast() + (usecs << 12); 115 while (get_tod_clock_fast() < end) 116 cpu_relax(); 117 } 118 119 void __ndelay(unsigned long long nsecs) 120 { 121 u64 end; 122 123 nsecs <<= 9; 124 do_div(nsecs, 125); 125 end = get_tod_clock_fast() + nsecs; 126 if (nsecs & ~0xfffUL) 127 __udelay(nsecs >> 12); 128 while (get_tod_clock_fast() < end) 129 barrier(); 130 } 131 EXPORT_SYMBOL(__ndelay); 132