arch/s390/lib/delay.c

   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/module.h>
  13 #include <linux/irqflags.h>
  14 #include <linux/interrupt.h>
  15 #include <asm/div64.h>
  16
  17 void __delay(unsigned long loops)
  18 {
  19         /*
  20          * To end the bloody studid and useless discussion about the
  21          * BogoMips number I took the liberty to define the __delay
  22          * function in a way that that resulting BogoMips number will
  23          * yield the megahertz number of the cpu. The important function
  24          * is udelay and that is done using the tod clock. -- martin.
  25          */
  26         asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
  27 }
  28
  29 static void __udelay_disabled(unsigned long long usecs)
  30 {
  31         unsigned long mask, cr0, cr0_saved;
  32         u64 clock_saved;
  33         u64 end;
  34
  35         mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
  36         end = get_clock() + (usecs << 12);
  37         clock_saved = local_tick_disable();
  38         __ctl_store(cr0_saved, 0, 0);
  39         cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
  40         __ctl_load(cr0 , 0, 0);
  41         lockdep_off();
  42         do {
  43                 set_clock_comparator(end);
  44                 trace_hardirqs_on();
  45                 __load_psw_mask(mask);
  46                 local_irq_disable();
  47         } while (get_clock() < end);
  48         lockdep_on();
  49         __ctl_load(cr0_saved, 0, 0);
  50         local_tick_enable(clock_saved);
  51 }
  52
  53 static void __udelay_enabled(unsigned long long usecs)
  54 {
  55         unsigned long mask;
  56         u64 clock_saved;
  57         u64 end;
  58
  59         mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
  60         end = get_clock() + (usecs << 12);
  61         do {
  62                 clock_saved = 0;
  63                 if (end < S390_lowcore.clock_comparator) {
  64                         clock_saved = local_tick_disable();
  65                         set_clock_comparator(end);
  66                 }
  67                 trace_hardirqs_on();
  68                 __load_psw_mask(mask);
  69                 local_irq_disable();
  70                 if (clock_saved)
  71                         local_tick_enable(clock_saved);
  72         } while (get_clock() < end);
  73 }
  74
  75 /*
  76  * Waits for 'usecs' microseconds using the TOD clock comparator.
  77  */
  78 void __udelay(unsigned long long usecs)
  79 {
  80         unsigned long flags;
  81
  82         preempt_disable();
  83         local_irq_save(flags);
  84         if (in_irq()) {
  85                 __udelay_disabled(usecs);
  86                 goto out;
  87         }
  88         if (in_softirq()) {
  89                 if (raw_irqs_disabled_flags(flags))
  90                         __udelay_disabled(usecs);
  91                 else
  92                         __udelay_enabled(usecs);
  93                 goto out;
  94         }
  95         if (raw_irqs_disabled_flags(flags)) {
  96                 local_bh_disable();
  97                 __udelay_disabled(usecs);
  98                 _local_bh_enable();
  99                 goto out;
 100         }
 101         __udelay_enabled(usecs);
 102 out:
 103         local_irq_restore(flags);
 104         preempt_enable();
 105 }
 106 EXPORT_SYMBOL(__udelay);
 107
 108 /*
 109  * Simple udelay variant. To be used on startup and reboot
 110  * when the interrupt handler isn't working.
 111  */
 112 void udelay_simple(unsigned long long usecs)
 113 {
 114         u64 end;
 115
 116         end = get_clock() + (usecs << 12);
 117         while (get_clock() < end)
 118                 cpu_relax();
 119 }
 120
 121 void __ndelay(unsigned long long nsecs)
 122 {
 123         u64 end;
 124
 125         nsecs <<= 9;
 126         do_div(nsecs, 125);
 127         end = get_clock() + nsecs;
 128         if (nsecs & ~0xfffUL)
 129                 __udelay(nsecs >> 12);
 130         while (get_clock() < end)
 131                 barrier();
 132 }
 133 EXPORT_SYMBOL(__ndelay);