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/vtimer.h>
  16 #include <asm/div64.h>
  17
  18 void __delay(unsigned long loops)
  19 {
  20         /*
  21          * To end the bloody studid and useless discussion about the
  22          * BogoMips number I took the liberty to define the __delay
  23          * function in a way that that resulting BogoMips number will
  24          * yield the megahertz number of the cpu. The important function
  25          * is udelay and that is done using the tod clock. -- martin.
  26          */
  27         asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
  28 }
  29 EXPORT_SYMBOL(__delay);
  30
  31 static void __udelay_disabled(unsigned long long usecs)
  32 {
  33         unsigned long cr0, cr6, new;
  34         u64 clock_saved, end;
  35
  36         end = get_tod_clock() + (usecs << 12);
  37         clock_saved = local_tick_disable();
  38         __ctl_store(cr0, 0, 0);
  39         __ctl_store(cr6, 6, 6);
  40         new = (cr0 &  0xffff00e0) | 0x00000800;
  41         __ctl_load(new , 0, 0);
  42         new = 0;
  43         __ctl_load(new, 6, 6);
  44         lockdep_off();
  45         do {
  46                 set_clock_comparator(end);
  47                 enabled_wait();
  48         } while (get_tod_clock_fast() < end);
  49         lockdep_on();
  50         __ctl_load(cr0, 0, 0);
  51         __ctl_load(cr6, 6, 6);
  52         local_tick_enable(clock_saved);
  53 }
  54
  55 static void __udelay_enabled(unsigned long long usecs)
  56 {
  57         u64 clock_saved, end;
  58
  59         end = get_tod_clock_fast() + (usecs << 12);
  60         do {
  61                 clock_saved = 0;
  62                 if (end < S390_lowcore.clock_comparator) {
  63                         clock_saved = local_tick_disable();
  64                         set_clock_comparator(end);
  65                 }
  66                 enabled_wait();
  67                 if (clock_saved)
  68                         local_tick_enable(clock_saved);
  69         } while (get_tod_clock_fast() < end);
  70 }
  71
  72 /*
  73  * Waits for 'usecs' microseconds using the TOD clock comparator.
  74  */
  75 void __udelay(unsigned long long usecs)
  76 {
  77         unsigned long flags;
  78
  79         preempt_disable();
  80         local_irq_save(flags);
  81         if (in_irq()) {
  82                 __udelay_disabled(usecs);
  83                 goto out;
  84         }
  85         if (in_softirq()) {
  86                 if (raw_irqs_disabled_flags(flags))
  87                         __udelay_disabled(usecs);
  88                 else
  89                         __udelay_enabled(usecs);
  90                 goto out;
  91         }
  92         if (raw_irqs_disabled_flags(flags)) {
  93                 local_bh_disable();
  94                 __udelay_disabled(usecs);
  95                 _local_bh_enable();
  96                 goto out;
  97         }
  98         __udelay_enabled(usecs);
  99 out:
 100         local_irq_restore(flags);
 101         preempt_enable();
 102 }
 103 EXPORT_SYMBOL(__udelay);
 104
 105 /*
 106  * Simple udelay variant. To be used on startup and reboot
 107  * when the interrupt handler isn't working.
 108  */
 109 void udelay_simple(unsigned long long usecs)
 110 {
 111         u64 end;
 112
 113         end = get_tod_clock_fast() + (usecs << 12);
 114         while (get_tod_clock_fast() < end)
 115                 cpu_relax();
 116 }
 117
 118 void __ndelay(unsigned long long nsecs)
 119 {
 120         u64 end;
 121
 122         nsecs <<= 9;
 123         do_div(nsecs, 125);
 124         end = get_tod_clock_fast() + nsecs;
 125         if (nsecs & ~0xfffUL)
 126                 __udelay(nsecs >> 12);
 127         while (get_tod_clock_fast() < end)
 128                 barrier();
 129 }
 130 EXPORT_SYMBOL(__ndelay);