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
__delay(unsigned long loops)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
__udelay_disabled(unsigned long long usecs)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
__udelay_enabled(unsigned long long usecs)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 */
__udelay(unsigned long long usecs)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 */
udelay_simple(unsigned long long usecs)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
__ndelay(unsigned long long nsecs)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