xref: /openbmc/linux/arch/s390/lib/delay.c (revision dfe94d40)
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/jump_label.h>
17 #include <linux/irq.h>
18 #include <asm/vtimer.h>
19 #include <asm/div64.h>
20 #include <asm/idle.h>
21 
22 void __delay(unsigned long loops)
23 {
24         /*
25          * To end the bloody studid and useless discussion about the
26          * BogoMips number I took the liberty to define the __delay
27          * function in a way that that resulting BogoMips number will
28          * yield the megahertz number of the cpu. The important function
29          * is udelay and that is done using the tod clock. -- martin.
30          */
31 	asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
32 }
33 EXPORT_SYMBOL(__delay);
34 
35 static void delay_loop(unsigned long delta)
36 {
37 	unsigned long end;
38 
39 	end = get_tod_clock_monotonic() + delta;
40 	while (!tod_after(get_tod_clock_monotonic(), end))
41 		cpu_relax();
42 }
43 
44 void __udelay(unsigned long usecs)
45 {
46 	delay_loop(usecs << 12);
47 }
48 EXPORT_SYMBOL(__udelay);
49 
50 void __ndelay(unsigned long nsecs)
51 {
52 	nsecs <<= 9;
53 	do_div(nsecs, 125);
54 	delay_loop(nsecs);
55 }
56 EXPORT_SYMBOL(__ndelay);
57