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         lockdep_off();
  40         trace_hardirqs_on();
  41         __load_psw_mask(mask);
  42         local_irq_disable();
  43         lockdep_on();
  44         __ctl_load(cr0_saved, 0, 0);
  45         local_tick_enable(clock_saved);
  46         set_clock_comparator(S390_lowcore.clock_comparator);
  47 }
  48
  49 static void __udelay_enabled(unsigned long usecs)
  50 {
  51         unsigned long mask;
  52         u64 clock_saved;
  53         u64 end;
  54
  55         mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
  56         end = get_clock() + ((u64) usecs << 12);
  57         do {
  58                 clock_saved = 0;
  59                 if (end < S390_lowcore.clock_comparator) {
  60                         clock_saved = local_tick_disable();
  61                         set_clock_comparator(end);
  62                 }
  63                 trace_hardirqs_on();
  64                 __load_psw_mask(mask);
  65                 local_irq_disable();
  66                 if (clock_saved)
  67                         local_tick_enable(clock_saved);
  68         } while (get_clock() < end);
  69         set_clock_comparator(S390_lowcore.clock_comparator);
  70 }
  71
  72 /*
  73  * Waits for 'usecs' microseconds using the TOD clock comparator.
  74  */
  75 void __udelay(unsigned 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 usecs)
 110 {
 111         u64 end;
 112
 113         end = get_clock() + ((u64) usecs << 12);
 114         while (get_clock() < end)
 115                 cpu_relax();
 116 }