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_DAT | PSW_MASK_WAIT |
  36                 PSW_MASK_EXT | PSW_MASK_MCHECK;
  37         end = get_clock() + (usecs << 12);
  38         clock_saved = local_tick_disable();
  39         __ctl_store(cr0_saved, 0, 0);
  40         cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
  41         __ctl_load(cr0 , 0, 0);
  42         lockdep_off();
  43         do {
  44                 set_clock_comparator(end);
  45                 trace_hardirqs_on();
  46                 __load_psw_mask(mask);
  47                 local_irq_disable();
  48         } while (get_clock() < end);
  49         lockdep_on();
  50         __ctl_load(cr0_saved, 0, 0);
  51         local_tick_enable(clock_saved);
  52 }
  53
  54 static void __udelay_enabled(unsigned long long usecs)
  55 {
  56         unsigned long mask;
  57         u64 clock_saved;
  58         u64 end;
  59
  60         mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
  61         end = get_clock() + (usecs << 12);
  62         do {
  63                 clock_saved = 0;
  64                 if (end < S390_lowcore.clock_comparator) {
  65                         clock_saved = local_tick_disable();
  66                         set_clock_comparator(end);
  67                 }
  68                 trace_hardirqs_on();
  69                 __load_psw_mask(mask);
  70                 local_irq_disable();
  71                 if (clock_saved)
  72                         local_tick_enable(clock_saved);
  73         } while (get_clock() < end);
  74 }
  75
  76 /*
  77  * Waits for 'usecs' microseconds using the TOD clock comparator.
  78  */
  79 void __udelay(unsigned long long usecs)
  80 {
  81         unsigned long flags;
  82
  83         preempt_disable();
  84         local_irq_save(flags);
  85         if (in_irq()) {
  86                 __udelay_disabled(usecs);
  87                 goto out;
  88         }
  89         if (in_softirq()) {
  90                 if (raw_irqs_disabled_flags(flags))
  91                         __udelay_disabled(usecs);
  92                 else
  93                         __udelay_enabled(usecs);
  94                 goto out;
  95         }
  96         if (raw_irqs_disabled_flags(flags)) {
  97                 local_bh_disable();
  98                 __udelay_disabled(usecs);
  99                 _local_bh_enable();
 100                 goto out;
 101         }
 102         __udelay_enabled(usecs);
 103 out:
 104         local_irq_restore(flags);
 105         preempt_enable();
 106 }
 107 EXPORT_SYMBOL(__udelay);
 108
 109 /*
 110  * Simple udelay variant. To be used on startup and reboot
 111  * when the interrupt handler isn't working.
 112  */
 113 void udelay_simple(unsigned long long usecs)
 114 {
 115         u64 end;
 116
 117         end = get_clock() + (usecs << 12);
 118         while (get_clock() < end)
 119                 cpu_relax();
 120 }
 121
 122 void __ndelay(unsigned long long nsecs)
 123 {
 124         u64 end;
 125
 126         nsecs <<= 9;
 127         do_div(nsecs, 125);
 128         end = get_clock() + nsecs;
 129         if (nsecs & ~0xfffUL)
 130                 __udelay(nsecs >> 12);
 131         while (get_clock() < end)
 132                 barrier();
 133 }
 134 EXPORT_SYMBOL(__ndelay);