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/div64.h>
16
__delay(unsigned long loops)17 void __delay(unsigned long loops)
18 {
19 /*
20 * To end the bloody studid and useless discussion about the
21 * BogoMips number I took the liberty to define the __delay
22 * function in a way that that resulting BogoMips number will
23 * yield the megahertz number of the cpu. The important function
24 * is udelay and that is done using the tod clock. -- martin.
25 */
26 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
27 }
28
__udelay_disabled(unsigned long long usecs)29 static void __udelay_disabled(unsigned long long usecs)
30 {
31 unsigned long mask, cr0, cr0_saved;
32 u64 clock_saved;
33 u64 end;
34
35 mask = psw_kernel_bits | PSW_MASK_DAT | PSW_MASK_WAIT |
36 PSW_MASK_EXT | PSW_MASK_MCHECK;
37 end = get_clock() + (usecs << 12);
38 clock_saved = local_tick_disable();
39 __ctl_store(cr0_saved, 0, 0);
40 cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
41 __ctl_load(cr0 , 0, 0);
42 lockdep_off();
43 do {
44 set_clock_comparator(end);
45 trace_hardirqs_on();
46 __load_psw_mask(mask);
47 local_irq_disable();
48 } while (get_clock() < end);
49 lockdep_on();
50 __ctl_load(cr0_saved, 0, 0);
51 local_tick_enable(clock_saved);
52 }
53
__udelay_enabled(unsigned long long usecs)54 static void __udelay_enabled(unsigned long long usecs)
55 {
56 unsigned long mask;
57 u64 clock_saved;
58 u64 end;
59
60 mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
61 end = get_clock() + (usecs << 12);
62 do {
63 clock_saved = 0;
64 if (end < S390_lowcore.clock_comparator) {
65 clock_saved = local_tick_disable();
66 set_clock_comparator(end);
67 }
68 trace_hardirqs_on();
69 __load_psw_mask(mask);
70 local_irq_disable();
71 if (clock_saved)
72 local_tick_enable(clock_saved);
73 } while (get_clock() < end);
74 }
75
76 /*
77 * Waits for 'usecs' microseconds using the TOD clock comparator.
78 */
__udelay(unsigned long long usecs)79 void __udelay(unsigned long long usecs)
80 {
81 unsigned long flags;
82
83 preempt_disable();
84 local_irq_save(flags);
85 if (in_irq()) {
86 __udelay_disabled(usecs);
87 goto out;
88 }
89 if (in_softirq()) {
90 if (raw_irqs_disabled_flags(flags))
91 __udelay_disabled(usecs);
92 else
93 __udelay_enabled(usecs);
94 goto out;
95 }
96 if (raw_irqs_disabled_flags(flags)) {
97 local_bh_disable();
98 __udelay_disabled(usecs);
99 _local_bh_enable();
100 goto out;
101 }
102 __udelay_enabled(usecs);
103 out:
104 local_irq_restore(flags);
105 preempt_enable();
106 }
107 EXPORT_SYMBOL(__udelay);
108
109 /*
110 * Simple udelay variant. To be used on startup and reboot
111 * when the interrupt handler isn't working.
112 */
udelay_simple(unsigned long long usecs)113 void udelay_simple(unsigned long long usecs)
114 {
115 u64 end;
116
117 end = get_clock() + (usecs << 12);
118 while (get_clock() < end)
119 cpu_relax();
120 }
121
__ndelay(unsigned long long nsecs)122 void __ndelay(unsigned long long nsecs)
123 {
124 u64 end;
125
126 nsecs <<= 9;
127 do_div(nsecs, 125);
128 end = get_clock() + nsecs;
129 if (nsecs & ~0xfffUL)
130 __udelay(nsecs >> 12);
131 while (get_clock() < end)
132 barrier();
133 }
134 EXPORT_SYMBOL(__ndelay);
135