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 usecs)
  29 {
  30         unsigned long mask, cr0, cr0_saved;
  31         u64 clock_saved;
  32
  33         clock_saved = local_tick_disable();
  34         set_clock_comparator(get_clock() + ((u64) usecs << 12));
  35         __ctl_store(cr0_saved, 0, 0);
  36         cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
  37         __ctl_load(cr0 , 0, 0);
  38         mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
  39         trace_hardirqs_on();
  40         __load_psw_mask(mask);
  41         local_irq_disable();
  42         __ctl_load(cr0_saved, 0, 0);
  43         local_tick_enable(clock_saved);
  44         set_clock_comparator(S390_lowcore.clock_comparator);
  45 }
  46
  47 static void __udelay_enabled(unsigned long usecs)
  48 {
  49         unsigned long mask;
  50         u64 end, time;
  51
  52         mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
  53         end = get_clock() + ((u64) usecs << 12);
  54         do {
  55                 time = end < S390_lowcore.clock_comparator ?
  56                         end : S390_lowcore.clock_comparator;
  57                 set_clock_comparator(time);
  58                 trace_hardirqs_on();
  59                 __load_psw_mask(mask);
  60                 local_irq_disable();
  61         } while (get_clock() < end);
  62         set_clock_comparator(S390_lowcore.clock_comparator);
  63 }
  64
  65 /*
  66  * Waits for 'usecs' microseconds using the TOD clock comparator.
  67  */
  68 void __udelay(unsigned long usecs)
  69 {
  70         unsigned long flags;
  71
  72         preempt_disable();
  73         local_irq_save(flags);
  74         if (in_irq()) {
  75                 __udelay_disabled(usecs);
  76                 goto out;
  77         }
  78         if (in_softirq()) {
  79                 if (raw_irqs_disabled_flags(flags))
  80                         __udelay_disabled(usecs);
  81                 else
  82                         __udelay_enabled(usecs);
  83                 goto out;
  84         }
  85         if (raw_irqs_disabled_flags(flags)) {
  86                 local_bh_disable();
  87                 __udelay_disabled(usecs);
  88                 _local_bh_enable();
  89                 goto out;
  90         }
  91         __udelay_enabled(usecs);
  92 out:
  93         local_irq_restore(flags);
  94         preempt_enable();
  95 }
  96 EXPORT_SYMBOL(__udelay);
  97
  98 /*
  99  * Simple udelay variant. To be used on startup and reboot
 100  * when the interrupt handler isn't working.
 101  */
 102 void udelay_simple(unsigned long usecs)
 103 {
 104         u64 end;
 105
 106         end = get_clock() + ((u64) usecs << 12);
 107         while (get_clock() < end)
 108                 cpu_relax();
 109 }