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
  30 static void __udelay_disabled(unsigned long long usecs)
  31 {
  32         unsigned long cr0, cr6, new;
  33         u64 clock_saved, end;
  34
  35         end = get_tod_clock() + (usecs << 12);
  36         clock_saved = local_tick_disable();
  37         __ctl_store(cr0, 0, 0);
  38         __ctl_store(cr6, 6, 6);
  39         new = (cr0 &  0xffff00e0) | 0x00000800;
  40         __ctl_load(new , 0, 0);
  41         new = 0;
  42         __ctl_load(new, 6, 6);
  43         lockdep_off();
  44         do {
  45                 set_clock_comparator(end);
  46                 vtime_stop_cpu();
  47                 local_irq_disable();
  48         } while (get_tod_clock() < 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() + (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                 vtime_stop_cpu();
  67                 local_irq_disable();
  68                 if (clock_saved)
  69                         local_tick_enable(clock_saved);
  70         } while (get_tod_clock() < end);
  71 }
  72
  73 /*
  74  * Waits for 'usecs' microseconds using the TOD clock comparator.
  75  */
  76 void __udelay(unsigned long long usecs)
  77 {
  78         unsigned long flags;
  79
  80         preempt_disable();
  81         local_irq_save(flags);
  82         if (in_irq()) {
  83                 __udelay_disabled(usecs);
  84                 goto out;
  85         }
  86         if (in_softirq()) {
  87                 if (raw_irqs_disabled_flags(flags))
  88                         __udelay_disabled(usecs);
  89                 else
  90                         __udelay_enabled(usecs);
  91                 goto out;
  92         }
  93         if (raw_irqs_disabled_flags(flags)) {
  94                 local_bh_disable();
  95                 __udelay_disabled(usecs);
  96                 _local_bh_enable();
  97                 goto out;
  98         }
  99         __udelay_enabled(usecs);
 100 out:
 101         local_irq_restore(flags);
 102         preempt_enable();
 103 }
 104 EXPORT_SYMBOL(__udelay);
 105
 106 /*
 107  * Simple udelay variant. To be used on startup and reboot
 108  * when the interrupt handler isn't working.
 109  */
 110 void udelay_simple(unsigned long long usecs)
 111 {
 112         u64 end;
 113
 114         end = get_tod_clock() + (usecs << 12);
 115         while (get_tod_clock() < end)
 116                 cpu_relax();
 117 }
 118
 119 void __ndelay(unsigned long long nsecs)
 120 {
 121         u64 end;
 122
 123         nsecs <<= 9;
 124         do_div(nsecs, 125);
 125         end = get_tod_clock() + nsecs;
 126         if (nsecs & ~0xfffUL)
 127                 __udelay(nsecs >> 12);
 128         while (get_tod_clock() < end)
 129                 barrier();
 130 }
 131 EXPORT_SYMBOL(__ndelay);