sys/dev/acpi/acpi_timer.c

   1 /* $NetBSD: acpi_timer.c,v 1.13 2009/03/15 15:42:55 cegger Exp $ */
   2
   3 #include <sys/cdefs.h>
   4 __KERNEL_RCSID(0, "$NetBSD: acpi_timer.c,v 1.13 2009/03/15 15:42:55 cegger Exp $");
   5
   6 #include <sys/types.h>
   7 #include <sys/systm.h>
   8 #include <sys/time.h>
   9 #include <sys/timetc.h>
  10 #include <dev/acpi/acpica.h>
  11 #include <dev/acpi/acpi_timer.h>
  12 #include <machine/acpi_machdep.h>
  13
  14 static int acpitimer_test(void);
  15 static uint32_t acpitimer_delta(uint32_t, uint32_t);
  16 static u_int acpitimer_read_safe(struct timecounter *);
  17 static u_int acpitimer_read_fast(struct timecounter *);
  18
  19 static struct timecounter acpi_timecounter = {
  20         acpitimer_read_safe,
  21         0,
  22         0x00ffffff,
  23         PM_TIMER_FREQUENCY,
  24         "ACPI-Safe",
  25         900,
  26         NULL,
  27         NULL,
  28 };
  29
  30 int
  31 acpitimer_init(void)
  32 {
  33         uint32_t bits;
  34         int i, j;
  35         ACPI_STATUS res;
  36
  37         res = AcpiGetTimerResolution(&bits);
  38         if (res != AE_OK)
  39                 return (-1);
  40
  41         if (bits == 32)
  42                 acpi_timecounter.tc_counter_mask = 0xffffffff;
  43
  44         j = 0;
  45         for (i = 0; i < 10; i++)
  46                 j += acpitimer_test();
  47
  48         if (j >= 10) {
  49                 acpi_timecounter.tc_name = "ACPI-Fast";
  50                 acpi_timecounter.tc_get_timecount = acpitimer_read_fast;
  51                 acpi_timecounter.tc_quality = 1000;
  52         }
  53
  54         tc_init(&acpi_timecounter);
  55         aprint_verbose("%s %d-bit timer\n", acpi_timecounter.tc_name, bits);
  56
  57         return (0);
  58 }
  59
  60 int
  61 acpitimer_detach(void)
  62 {
  63         return tc_detach(&acpi_timecounter);
  64 }
  65
  66 static u_int
  67 acpitimer_read_fast(struct timecounter *tc)
  68 {
  69         uint32_t t;
  70
  71         AcpiGetTimer(&t);
  72         return (t);
  73 }
  74
  75 /*
  76  * Some chipsets (PIIX4 variants) do not latch correctly; there
  77  * is a chance that a transition is hit.
  78  */
  79 static u_int
  80 acpitimer_read_safe(struct timecounter *tc)
  81 {
  82         uint32_t t1, t2, t3;
  83
  84         AcpiGetTimer(&t2);
  85         AcpiGetTimer(&t3);
  86         do {
  87                 t1 = t2;
  88                 t2 = t3;
  89                 AcpiGetTimer(&t3);
  90         } while ((t1 > t2) || (t2 > t3));
  91         return (t2);
  92 }
  93
  94 static uint32_t
  95 acpitimer_delta(uint32_t end, uint32_t start)
  96 {
  97         uint32_t delta;
  98         u_int mask = acpi_timecounter.tc_counter_mask;
  99
 100         if (end >= start)
 101                 delta = end - start;
 102         else
 103                 delta = ((mask - start) + end + 1) & mask;
 104
 105         return (delta);
 106 }
 107
 108 #define N 2000
 109 static int
 110 acpitimer_test(void)
 111 {
 112         uint32_t last, this, delta;
 113         int minl, maxl, n;
 114
 115         minl = 10000000;
 116         maxl = 0;
 117
 118         acpi_md_OsDisableInterrupt();
 119         AcpiGetTimer(&last);
 120         for (n = 0; n < N; n++) {
 121                 AcpiGetTimer(&this);
 122                 delta = acpitimer_delta(this, last);
 123                 if (delta > maxl)
 124                         maxl = delta;
 125                 else if (delta < minl)
 126                         minl = delta;
 127                 last = this;
 128         }
 129         acpi_md_OsEnableInterrupt();
 130
 131         if (maxl - minl > 2 )
 132                 n = 0;
 133         else if (minl < 0 || maxl == 0)
 134                 n = 0;
 135         else
 136                 n = 1;
 137
 138         return (n);
 139 }