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