tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
16void __delay(unsigned long loops)
17{
18 /*
19 * To end the bloody studid and useless discussion about the
20 * BogoMips number I took the liberty to define the __delay
21 * function in a way that that resulting BogoMips number will
22 * yield the megahertz number of the cpu. The important function
23 * is udelay and that is done using the tod clock. -- martin.
24 */
25 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
26}
27
28static void __udelay_disabled(unsigned long long usecs)
29{
30 unsigned long mask, cr0, cr0_saved;
31 u64 clock_saved;
32
33 clock_saved = local_tick_disable();
34 set_clock_comparator(get_clock() + (usecs << 12));
35 __ctl_store(cr0_saved, 0, 0);
36 cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
37 __ctl_load(cr0 , 0, 0);
38 mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
39 lockdep_off();
40 trace_hardirqs_on();
41 __load_psw_mask(mask);
42 local_irq_disable();
43 lockdep_on();
44 __ctl_load(cr0_saved, 0, 0);
45 local_tick_enable(clock_saved);
46 set_clock_comparator(S390_lowcore.clock_comparator);
47}
48
49static void __udelay_enabled(unsigned long long usecs)
50{
51 unsigned long mask;
52 u64 clock_saved;
53 u64 end;
54
55 mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
56 end = get_clock() + (usecs << 12);
57 do {
58 clock_saved = 0;
59 if (end < S390_lowcore.clock_comparator) {
60 clock_saved = local_tick_disable();
61 set_clock_comparator(end);
62 }
63 trace_hardirqs_on();
64 __load_psw_mask(mask);
65 local_irq_disable();
66 if (clock_saved)
67 local_tick_enable(clock_saved);
68 } while (get_clock() < end);
69 set_clock_comparator(S390_lowcore.clock_comparator);
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_clock() + (usecs << 12);
114 while (get_clock() < end)
115 cpu_relax();
116}