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 <linux/irq.h>
  16 #include <asm/vtimer.h>
  17 #include <asm/div64.h>
  18 #include <asm/idle.h>
  19
  20 void __delay(unsigned long loops)
  21 {
  22         /*
  23          * To end the bloody studid and useless discussion about the
  24          * BogoMips number I took the liberty to define the __delay
  25          * function in a way that that resulting BogoMips number will
  26          * yield the megahertz number of the cpu. The important function
  27          * is udelay and that is done using the tod clock. -- martin.
  28          */
  29         asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
  30 }
  31 EXPORT_SYMBOL(__delay);
  32
  33 static void __udelay_disabled(unsigned long long usecs)
  34 {
  35         unsigned long cr0, cr0_new, psw_mask;
  36         struct s390_idle_data idle;
  37         u64 end;
  38
  39         end = get_tod_clock() + (usecs << 12);
  40         __ctl_store(cr0, 0, 0);
  41         cr0_new = cr0 & ~CR0_IRQ_SUBCLASS_MASK;
  42         cr0_new |= (1UL << (63 - 52)); /* enable clock comparator irq */
  43         __ctl_load(cr0_new, 0, 0);
  44         psw_mask = __extract_psw() | PSW_MASK_EXT | PSW_MASK_WAIT;
  45         set_clock_comparator(end);
  46         set_cpu_flag(CIF_IGNORE_IRQ);
  47         psw_idle(&idle, psw_mask);
  48         clear_cpu_flag(CIF_IGNORE_IRQ);
  49         set_clock_comparator(S390_lowcore.clock_comparator);
  50         __ctl_load(cr0, 0, 0);
  51 }
  52
  53 static void __udelay_enabled(unsigned long long usecs)
  54 {
  55         u64 clock_saved, end;
  56
  57         end = get_tod_clock_fast() + (usecs << 12);
  58         do {
  59                 clock_saved = 0;
  60                 if (end < S390_lowcore.clock_comparator) {
  61                         clock_saved = local_tick_disable();
  62                         set_clock_comparator(end);
  63                 }
  64                 enabled_wait();
  65                 if (clock_saved)
  66                         local_tick_enable(clock_saved);
  67         } while (get_tod_clock_fast() < end);
  68 }
  69
  70 /*
  71  * Waits for 'usecs' microseconds using the TOD clock comparator.
  72  */
  73 void __udelay(unsigned long long usecs)
  74 {
  75         unsigned long flags;
  76
  77         preempt_disable();
  78         local_irq_save(flags);
  79         if (in_irq()) {
  80                 __udelay_disabled(usecs);
  81                 goto out;
  82         }
  83         if (in_softirq()) {
  84                 if (raw_irqs_disabled_flags(flags))
  85                         __udelay_disabled(usecs);
  86                 else
  87                         __udelay_enabled(usecs);
  88                 goto out;
  89         }
  90         if (raw_irqs_disabled_flags(flags)) {
  91                 local_bh_disable();
  92                 __udelay_disabled(usecs);
  93                 _local_bh_enable();
  94                 goto out;
  95         }
  96         __udelay_enabled(usecs);
  97 out:
  98         local_irq_restore(flags);
  99         preempt_enable();
 100 }
 101 EXPORT_SYMBOL(__udelay);
 102
 103 /*
 104  * Simple udelay variant. To be used on startup and reboot
 105  * when the interrupt handler isn't working.
 106  */
 107 void udelay_simple(unsigned long long usecs)
 108 {
 109         u64 end;
 110
 111         end = get_tod_clock_fast() + (usecs << 12);
 112         while (get_tod_clock_fast() < end)
 113                 cpu_relax();
 114 }
 115
 116 void __ndelay(unsigned long long nsecs)
 117 {
 118         u64 end;
 119
 120         nsecs <<= 9;
 121         do_div(nsecs, 125);
 122         end = get_tod_clock_fast() + nsecs;
 123         if (nsecs & ~0xfffUL)
 124                 __udelay(nsecs >> 12);
 125         while (get_tod_clock_fast() < end)
 126                 barrier();
 127 }
 128 EXPORT_SYMBOL(__ndelay);