arch/s390/lib/delay.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *    Precise Delay Loops for S390
   4  *
   5  *    Copyright IBM Corp. 1999, 2008
   6  *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
   7  *               Heiko Carstens <heiko.carstens@de.ibm.com>,
   8  */
   9
  10 #include <linux/sched.h>
  11 #include <linux/delay.h>
  12 #include <linux/timex.h>
  13 #include <linux/export.h>
  14 #include <linux/irqflags.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/irq.h>
  17 #include <asm/vtimer.h>
  18 #include <asm/div64.h>
  19 #include <asm/idle.h>
  20
  21 void __delay(unsigned long loops)
  22 {
  23         /*
  24          * To end the bloody studid and useless discussion about the
  25          * BogoMips number I took the liberty to define the __delay
  26          * function in a way that that resulting BogoMips number will
  27          * yield the megahertz number of the cpu. The important function
  28          * is udelay and that is done using the tod clock. -- martin.
  29          */
  30         asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
  31 }
  32 EXPORT_SYMBOL(__delay);
  33
  34 static void __udelay_disabled(unsigned long long usecs)
  35 {
  36         unsigned long cr0, cr0_new, psw_mask;
  37         struct s390_idle_data idle;
  38         u64 end;
  39
  40         end = get_tod_clock() + (usecs << 12);
  41         __ctl_store(cr0, 0, 0);
  42         cr0_new = cr0 & ~CR0_IRQ_SUBCLASS_MASK;
  43         cr0_new |= (1UL << (63 - 52)); /* enable clock comparator irq */
  44         __ctl_load(cr0_new, 0, 0);
  45         psw_mask = __extract_psw() | PSW_MASK_EXT | PSW_MASK_WAIT;
  46         set_clock_comparator(end);
  47         set_cpu_flag(CIF_IGNORE_IRQ);
  48         psw_idle(&idle, psw_mask);
  49         clear_cpu_flag(CIF_IGNORE_IRQ);
  50         set_clock_comparator(S390_lowcore.clock_comparator);
  51         __ctl_load(cr0, 0, 0);
  52 }
  53
  54 static void __udelay_enabled(unsigned long long usecs)
  55 {
  56         u64 clock_saved, end;
  57
  58         end = get_tod_clock_fast() + (usecs << 12);
  59         do {
  60                 clock_saved = 0;
  61                 if (tod_after(S390_lowcore.clock_comparator, end)) {
  62                         clock_saved = local_tick_disable();
  63                         set_clock_comparator(end);
  64                 }
  65                 enabled_wait();
  66                 if (clock_saved)
  67                         local_tick_enable(clock_saved);
  68         } while (get_tod_clock_fast() < end);
  69 }
  70
  71 /*
  72  * Waits for 'usecs' microseconds using the TOD clock comparator.
  73  */
  74 void __udelay(unsigned long long usecs)
  75 {
  76         unsigned long flags;
  77
  78         preempt_disable();
  79         local_irq_save(flags);
  80         if (in_irq()) {
  81                 __udelay_disabled(usecs);
  82                 goto out;
  83         }
  84         if (in_softirq()) {
  85                 if (raw_irqs_disabled_flags(flags))
  86                         __udelay_disabled(usecs);
  87                 else
  88                         __udelay_enabled(usecs);
  89                 goto out;
  90         }
  91         if (raw_irqs_disabled_flags(flags)) {
  92                 local_bh_disable();
  93                 __udelay_disabled(usecs);
  94                 _local_bh_enable();
  95                 goto out;
  96         }
  97         __udelay_enabled(usecs);
  98 out:
  99         local_irq_restore(flags);
 100         preempt_enable();
 101 }
 102 EXPORT_SYMBOL(__udelay);
 103
 104 /*
 105  * Simple udelay variant. To be used on startup and reboot
 106  * when the interrupt handler isn't working.
 107  */
 108 void udelay_simple(unsigned long long usecs)
 109 {
 110         u64 end;
 111
 112         end = get_tod_clock_fast() + (usecs << 12);
 113         while (get_tod_clock_fast() < end)
 114                 cpu_relax();
 115 }
 116
 117 void __ndelay(unsigned long long nsecs)
 118 {
 119         u64 end;
 120
 121         nsecs <<= 9;
 122         do_div(nsecs, 125);
 123         end = get_tod_clock_fast() + nsecs;
 124         if (nsecs & ~0xfffUL)
 125                 __udelay(nsecs >> 12);
 126         while (get_tod_clock_fast() < end)
 127                 barrier();
 128 }
 129 EXPORT_SYMBOL(__ndelay);