1 // SPDX-License-Identifier: GPL-2.0
3 * Precise Delay Loops for S390
5 * Copyright IBM Corp. 1999, 2008
6 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
7 * Heiko Carstens <heiko.carstens@de.ibm.com>,
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/irq.h>
17 #include <asm/vtimer.h>
18 #include <asm/div64.h>
21 void __delay(unsigned long loops)
24 * To end the bloody studid and useless discussion about the
25 * BogoMips number I took the liberty to define the __delay
26 * function in a way that that resulting BogoMips number will
27 * yield the megahertz number of the cpu. The important function
28 * is udelay and that is done using the tod clock. -- martin.
30 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
32 EXPORT_SYMBOL(__delay);
34 static void __udelay_disabled(unsigned long long usecs)
36 unsigned long cr0, cr0_new, psw_mask, flags;
37 struct s390_idle_data idle;
40 end = get_tod_clock() + (usecs << 12);
41 __ctl_store(cr0, 0, 0);
42 cr0_new = cr0 & ~CR0_IRQ_SUBCLASS_MASK;
43 cr0_new |= (1UL << (63 - 52)); /* enable clock comparator irq */
44 __ctl_load(cr0_new, 0, 0);
45 psw_mask = __extract_psw() | PSW_MASK_EXT | PSW_MASK_WAIT;
46 set_clock_comparator(end);
47 set_cpu_flag(CIF_IGNORE_IRQ);
48 local_irq_save(flags);
49 psw_idle(&idle, psw_mask);
50 local_irq_restore(flags);
51 clear_cpu_flag(CIF_IGNORE_IRQ);
52 set_clock_comparator(S390_lowcore.clock_comparator);
53 __ctl_load(cr0, 0, 0);
56 static void __udelay_enabled(unsigned long long usecs)
60 end = get_tod_clock_fast() + (usecs << 12);
63 if (tod_after(S390_lowcore.clock_comparator, end)) {
64 clock_saved = local_tick_disable();
65 set_clock_comparator(end);
69 local_tick_enable(clock_saved);
70 } while (get_tod_clock_fast() < end);
74 * Waits for 'usecs' microseconds using the TOD clock comparator.
76 void __udelay(unsigned long long usecs)
81 local_irq_save(flags);
83 __udelay_disabled(usecs);
87 if (raw_irqs_disabled_flags(flags))
88 __udelay_disabled(usecs);
90 __udelay_enabled(usecs);
93 if (raw_irqs_disabled_flags(flags)) {
95 __udelay_disabled(usecs);
99 __udelay_enabled(usecs);
101 local_irq_restore(flags);
104 EXPORT_SYMBOL(__udelay);
107 * Simple udelay variant. To be used on startup and reboot
108 * when the interrupt handler isn't working.
110 void udelay_simple(unsigned long long usecs)
114 end = get_tod_clock_fast() + (usecs << 12);
115 while (get_tod_clock_fast() < end)
119 void __ndelay(unsigned long long nsecs)
125 end = get_tod_clock_fast() + nsecs;
126 if (nsecs & ~0xfffUL)
127 __udelay(nsecs >> 12);
128 while (get_tod_clock_fast() < end)
131 EXPORT_SYMBOL(__ndelay);