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acpi_timer.c revision 1.19 
      1 /* $NetBSD: acpi_timer.c,v 1.19 2011/01/02 05:48:55 jruoho Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 2006 Matthias Drochner <drochner (at) NetBSD.org>
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 __KERNEL_RCSID(0, "$NetBSD: acpi_timer.c,v 1.19 2011/01/02 05:48:55 jruoho Exp $");
     31 
     32 #include <sys/types.h>
     33 #include <sys/systm.h>
     34 #include <sys/time.h>
     35 #include <sys/timetc.h>
     36 
     37 #include <dev/acpi/acpivar.h>
     38 #include <dev/acpi/acpi_timer.h>
     39 
     40 #include <machine/acpi_machdep.h>
     41 
     42 static int	acpitimer_test(void);
     43 
     44 static struct timecounter acpi_timecounter = {
     45 	acpitimer_read_safe,
     46 	0,
     47 	0x00ffffff,
     48 	PM_TIMER_FREQUENCY,
     49 	"ACPI-Safe",
     50 	900,
     51 	NULL,
     52 	NULL,
     53 };
     54 
     55 int
     56 acpitimer_init(struct acpi_softc *sc)
     57 {
     58 	const uint32_t flags = AcpiGbl_FADT.Flags;
     59 	ACPI_STATUS rv;
     60 	uint32_t bits;
     61 	int i, j;
     62 
     63 	rv = AcpiGetTimerResolution(&bits);
     64 
     65 	if (ACPI_FAILURE(rv))
     66 		return -1;
     67 
     68 	if (bits == 32)
     69 		acpi_timecounter.tc_counter_mask = 0xffffffff;
     70 
     71 	for (i = j = 0; i < 10; i++)
     72 		j += acpitimer_test();
     73 
     74 	if (j >= 10) {
     75 		acpi_timecounter.tc_name = "ACPI-Fast";
     76 		acpi_timecounter.tc_get_timecount = acpitimer_read_fast;
     77 		acpi_timecounter.tc_quality = 1000;
     78 	}
     79 
     80 	tc_init(&acpi_timecounter);
     81 
     82 	aprint_debug_dev(sc->sc_dev, "%s %d-bit timer\n",
     83 	    acpi_timecounter.tc_name, bits);
     84 
     85 	if ((flags & ACPI_FADT_PLATFORM_CLOCK) != 0)
     86 		aprint_debug_dev(sc->sc_dev,
     87 		    "warning: timer may be unreliable\n");
     88 
     89 	return 0;
     90 }
     91 
     92 int
     93 acpitimer_detach(void)
     94 {
     95 
     96 	return tc_detach(&acpi_timecounter);
     97 }
     98 
     99 u_int
    100 acpitimer_read_fast(struct timecounter *tc)
    101 {
    102 	uint32_t t;
    103 
    104 	(void)AcpiGetTimer(&t);
    105 
    106 	return t;
    107 }
    108 
    109 /*
    110  * Some chipsets (PIIX4 variants) do not latch correctly;
    111  * there is a chance that a transition is hit.
    112  */
    113 u_int
    114 acpitimer_read_safe(struct timecounter *tc)
    115 {
    116 	uint32_t t1, t2, t3;
    117 
    118 	(void)AcpiGetTimer(&t2);
    119 	(void)AcpiGetTimer(&t3);
    120 
    121 	do {
    122 		t1 = t2;
    123 		t2 = t3;
    124 
    125 		(void)AcpiGetTimer(&t3);
    126 
    127 	} while ((t1 > t2) || (t2 > t3));
    128 
    129 	return t2;
    130 }
    131 
    132 uint32_t
    133 acpitimer_delta(uint32_t end, uint32_t start)
    134 {
    135 	const u_int mask = acpi_timecounter.tc_counter_mask;
    136 	uint32_t delta;
    137 
    138 	if (end >= start)
    139 		delta = end - start;
    140 	else
    141 		delta = ((mask - start) + end + 1) & mask;
    142 
    143 	return delta;
    144 }
    145 
    146 #define N 2000
    147 
    148 static int
    149 acpitimer_test(void)
    150 {
    151 	uint32_t last, this, delta;
    152 	int minl, maxl, n;
    153 
    154 	minl = 10000000;
    155 	maxl = 0;
    156 
    157 	acpi_md_OsDisableInterrupt();
    158 
    159 	(void)AcpiGetTimer(&last);
    160 
    161 	for (n = 0; n < N; n++) {
    162 
    163 		(void)AcpiGetTimer(&this);
    164 
    165 		delta = acpitimer_delta(this, last);
    166 
    167 		if (delta > maxl)
    168 			maxl = delta;
    169 		else if (delta < minl)
    170 			minl = delta;
    171 
    172 		last = this;
    173 	}
    174 
    175 	acpi_md_OsEnableInterrupt();
    176 
    177 	if (maxl - minl > 2 )
    178 		n = 0;
    179 	else if (minl < 0 || maxl == 0)
    180 		n = 0;
    181 	else
    182 		n = 1;
    183 
    184 	return n;
    185 }
    186