xref: /kernel/linux/linux-5.10/arch/s390/lib/delay.c (revision 8c2ecf20) 
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
21void __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}
32EXPORT_SYMBOL(__delay);
33
34static 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
55static 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 */
75void __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);
99out:
100	local_irq_restore(flags);
101	preempt_enable();
102}
103EXPORT_SYMBOL(__udelay);
104
105/*
106 * Simple udelay variant. To be used on startup and reboot
107 * when the interrupt handler isn't working.
108 */
109void 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
118void __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}
130EXPORT_SYMBOL(__ndelay);
131