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
  16 void __delay(unsigned long loops)
  17 {
  18         /*
  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.
  24          */
  25         asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
  26 }
  27
  28 static void __udelay_disabled(unsigned long long usecs)
  29 {
  30         unsigned long mask, cr0, cr0_saved;
  31         u64 clock_saved;
  32         u64 end;
  33
  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);
  40         lockdep_off();
  41         do {
  42                 set_clock_comparator(end);
  43                 trace_hardirqs_on();
  44                 __load_psw_mask(mask);
  45                 local_irq_disable();
  46         } while (get_clock() < end);
  47         lockdep_on();
  48         __ctl_load(cr0_saved, 0, 0);
  49         local_tick_enable(clock_saved);
  50 }
  51
  52 static void __udelay_enabled(unsigned long long usecs)
  53 {
  54         unsigned long mask;
  55         u64 clock_saved;
  56         u64 end;
  57
  58         mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
  59         end = get_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                 trace_hardirqs_on();
  67                 __load_psw_mask(mask);
  68                 local_irq_disable();
  69                 if (clock_saved)
  70                         local_tick_enable(clock_saved);
  71         } while (get_clock() < end);
  72 }
  73
  74 /*
  75  * Waits for 'usecs' microseconds using the TOD clock comparator.
  76  */
  77 void __udelay(unsigned long long usecs)
  78 {
  79         unsigned long flags;
  80
  81         preempt_disable();
  82         local_irq_save(flags);
  83         if (in_irq()) {
  84                 __udelay_disabled(usecs);
  85                 goto out;
  86         }
  87         if (in_softirq()) {
  88                 if (raw_irqs_disabled_flags(flags))
  89                         __udelay_disabled(usecs);
  90                 else
  91                         __udelay_enabled(usecs);
  92                 goto out;
  93         }
  94         if (raw_irqs_disabled_flags(flags)) {
  95                 local_bh_disable();
  96                 __udelay_disabled(usecs);
  97                 _local_bh_enable();
  98                 goto out;
  99         }
 100         __udelay_enabled(usecs);
 101 out:
 102         local_irq_restore(flags);
 103         preempt_enable();
 104 }
 105 EXPORT_SYMBOL(__udelay);
 106
 107 /*
 108  * Simple udelay variant. To be used on startup and reboot
 109  * when the interrupt handler isn't working.
 110  */
 111 void udelay_simple(unsigned long long usecs)
 112 {
 113         u64 end;
 114
 115         end = get_clock() + (usecs << 12);
 116         while (get_clock() < end)
 117                 cpu_relax();
 118 }