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
);
52 static void __udelay_enabled(unsigned long long usecs
)
58 mask
= psw_kernel_bits
| PSW_MASK_WAIT
| PSW_MASK_EXT
| PSW_MASK_IO
;
59 end
= get_clock() + (usecs
<< 12);
62 if (end
< S390_lowcore
.clock_comparator
) {
63 clock_saved
= local_tick_disable();
64 set_clock_comparator(end
);
67 __load_psw_mask(mask
);
70 local_tick_enable(clock_saved
);
71 } while (get_clock() < end
);
75 * Waits for 'usecs' microseconds using the TOD clock comparator.
77 void __udelay(unsigned long long usecs
)
82 local_irq_save(flags
);
84 __udelay_disabled(usecs
);
88 if (raw_irqs_disabled_flags(flags
))
89 __udelay_disabled(usecs
);
91 __udelay_enabled(usecs
);
94 if (raw_irqs_disabled_flags(flags
)) {
96 __udelay_disabled(usecs
);
100 __udelay_enabled(usecs
);
102 local_irq_restore(flags
);
105 EXPORT_SYMBOL(__udelay
);
108 * Simple udelay variant. To be used on startup and reboot
109 * when the interrupt handler isn't working.
111 void udelay_simple(unsigned long long usecs
)
115 end
= get_clock() + (usecs
<< 12);
116 while (get_clock() < end
)
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