1/*
2 *    Precise Delay Loops for S390
3 *
4 *    Copyright IBM Corp. 1999, 2008
5 *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
6 *		 Heiko Carstens <heiko.carstens@de.ibm.com>,
7 */
8
9#include <linux/sched.h>
10#include <linux/delay.h>
11#include <linux/timex.h>
12#include <linux/module.h>
13#include <linux/irqflags.h>
14#include <linux/interrupt.h>
15#include <asm/vtimer.h>
16#include <asm/div64.h>
17
18void __delay(unsigned long loops)
19{
20        /*
21         * To end the bloody studid and useless discussion about the
22         * BogoMips number I took the liberty to define the __delay
23         * function in a way that that resulting BogoMips number will
24         * yield the megahertz number of the cpu. The important function
25         * is udelay and that is done using the tod clock. -- martin.
26         */
27	asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
28}
29
30static void __udelay_disabled(unsigned long long usecs)
31{
32	unsigned long cr0, cr6, new;
33	u64 clock_saved, end;
34
35	end = get_tod_clock() + (usecs << 12);
36	clock_saved = local_tick_disable();
37	__ctl_store(cr0, 0, 0);
38	__ctl_store(cr6, 6, 6);
39	new = (cr0 &  0xffff00e0) | 0x00000800;
40	__ctl_load(new , 0, 0);
41	new = 0;
42	__ctl_load(new, 6, 6);
43	lockdep_off();
44	do {
45		set_clock_comparator(end);
46		enabled_wait();
47	} while (get_tod_clock_fast() < end);
48	lockdep_on();
49	__ctl_load(cr0, 0, 0);
50	__ctl_load(cr6, 6, 6);
51	local_tick_enable(clock_saved);
52}
53
54static 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 (end < S390_lowcore.clock_comparator) {
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 */
74void __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);
98out:
99	local_irq_restore(flags);
100	preempt_enable();
101}
102EXPORT_SYMBOL(__udelay);
103
104/*
105 * Simple udelay variant. To be used on startup and reboot
106 * when the interrupt handler isn't working.
107 */
108void 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
117void __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}
129EXPORT_SYMBOL(__ndelay);
130