2 * Precise Delay Loops for S390
4 * Copyright IBM Corp. 1999,2008
5 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
6 * Heiko Carstens <heiko.carstens@de.ibm.com>,
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>
16 void __delay(unsigned long loops)
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.
25 asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
28 static void __udelay_disabled(unsigned long long usecs)
30 unsigned long mask, cr0, cr0_saved;
34 mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
35 end = get_clock() + (usecs << 12);
36 clock_saved = local_tick_disable();
37 __ctl_store(cr0_saved, 0, 0);
38 cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
39 __ctl_load(cr0 , 0, 0);
42 set_clock_comparator(end);
44 __load_psw_mask(mask);
46 } while (get_clock() < end);
48 __ctl_load(cr0_saved, 0, 0);
49 local_tick_enable(clock_saved);
50 set_clock_comparator(S390_lowcore.clock_comparator);
53 static void __udelay_enabled(unsigned long long usecs)
59 mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
60 end = get_clock() + (usecs << 12);
63 if (end < S390_lowcore.clock_comparator) {
64 clock_saved = local_tick_disable();
65 set_clock_comparator(end);
68 __load_psw_mask(mask);
71 local_tick_enable(clock_saved);
72 } while (get_clock() < end);
73 set_clock_comparator(S390_lowcore.clock_comparator);
77 * Waits for 'usecs' microseconds using the TOD clock comparator.
79 void __udelay(unsigned long long usecs)
84 local_irq_save(flags);
86 __udelay_disabled(usecs);
90 if (raw_irqs_disabled_flags(flags))
91 __udelay_disabled(usecs);
93 __udelay_enabled(usecs);
96 if (raw_irqs_disabled_flags(flags)) {
98 __udelay_disabled(usecs);
102 __udelay_enabled(usecs);
104 local_irq_restore(flags);
107 EXPORT_SYMBOL(__udelay);
110 * Simple udelay variant. To be used on startup and reboot
111 * when the interrupt handler isn't working.
113 void udelay_simple(unsigned long long usecs)
117 end = get_clock() + (usecs << 12);
118 while (get_clock() < end)