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