xref: /openbmc/linux/arch/s390/lib/delay.c (revision 9ac8d3fb)
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/irqflags.h>
13 #include <linux/interrupt.h>
14 
15 void __delay(unsigned long loops)
16 {
17         /*
18          * To end the bloody studid and useless discussion about the
19          * BogoMips number I took the liberty to define the __delay
20          * function in a way that that resulting BogoMips number will
21          * yield the megahertz number of the cpu. The important function
22          * is udelay and that is done using the tod clock. -- martin.
23          */
24 	asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
25 }
26 
27 static void __udelay_disabled(unsigned long usecs)
28 {
29 	unsigned long mask, cr0, cr0_saved;
30 	u64 clock_saved;
31 
32 	clock_saved = local_tick_disable();
33 	set_clock_comparator(get_clock() + ((u64) usecs << 12));
34 	__ctl_store(cr0_saved, 0, 0);
35 	cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
36 	__ctl_load(cr0 , 0, 0);
37 	mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
38 	trace_hardirqs_on();
39 	__load_psw_mask(mask);
40 	local_irq_disable();
41 	__ctl_load(cr0_saved, 0, 0);
42 	local_tick_enable(clock_saved);
43 	set_clock_comparator(S390_lowcore.clock_comparator);
44 }
45 
46 static void __udelay_enabled(unsigned long usecs)
47 {
48 	unsigned long mask;
49 	u64 end, time;
50 
51 	mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
52 	end = get_clock() + ((u64) usecs << 12);
53 	do {
54 		time = end < S390_lowcore.clock_comparator ?
55 			end : S390_lowcore.clock_comparator;
56 		set_clock_comparator(time);
57 		trace_hardirqs_on();
58 		__load_psw_mask(mask);
59 		local_irq_disable();
60 	} while (get_clock() < end);
61 	set_clock_comparator(S390_lowcore.clock_comparator);
62 }
63 
64 /*
65  * Waits for 'usecs' microseconds using the TOD clock comparator.
66  */
67 void __udelay(unsigned long usecs)
68 {
69 	unsigned long flags;
70 
71 	preempt_disable();
72 	local_irq_save(flags);
73 	if (in_irq()) {
74 		__udelay_disabled(usecs);
75 		goto out;
76 	}
77 	if (in_softirq()) {
78 		if (raw_irqs_disabled_flags(flags))
79 			__udelay_disabled(usecs);
80 		else
81 			__udelay_enabled(usecs);
82 		goto out;
83 	}
84 	if (raw_irqs_disabled_flags(flags)) {
85 		local_bh_disable();
86 		__udelay_disabled(usecs);
87 		_local_bh_enable();
88 		goto out;
89 	}
90 	__udelay_enabled(usecs);
91 out:
92 	local_irq_restore(flags);
93 	preempt_enable();
94 }
95 
96 /*
97  * Simple udelay variant. To be used on startup and reboot
98  * when the interrupt handler isn't working.
99  */
100 void udelay_simple(unsigned long usecs)
101 {
102 	u64 end;
103 
104 	end = get_clock() + ((u64) usecs << 12);
105 	while (get_clock() < end)
106 		cpu_relax();
107 }
108