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acpi_timer.c revision 1.23 
      1 /* $NetBSD: acpi_timer.c,v 1.23 2018/10/15 11:33:09 jmcneill 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 1.23 2018/10/15 11:33:09 jmcneill 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 	ACPI_PM_TIMER_FREQUENCY,
     49 	"ACPI-Safe",
     50 	900,
     51 	NULL,
     52 	NULL,
     53 };
     54 
     55 static bool
     56 acpitimer_supported(void)
     57 {
     58 	return AcpiGbl_FADT.PmTimerLength != 0;
     59 }
     60 
     61 int
     62 acpitimer_init(struct acpi_softc *sc)
     63 {
     64 	ACPI_STATUS rv;
     65 	uint32_t bits;
     66 	int i, j;
     67 
     68 	if (!acpitimer_supported())
     69 		return -1;
     70 
     71 	rv = AcpiGetTimerResolution(&bits);
     72 
     73 	if (ACPI_FAILURE(rv))
     74 		return -1;
     75 
     76 	if (bits == 32)
     77 		acpi_timecounter.tc_counter_mask = 0xffffffff;
     78 
     79 	for (i = j = 0; i < 10; i++)
     80 		j += acpitimer_test();
     81 
     82 	if (j >= 10) {
     83 		acpi_timecounter.tc_name = "ACPI-Fast";
     84 		acpi_timecounter.tc_get_timecount = acpitimer_read_fast;
     85 		acpi_timecounter.tc_quality = 1000;
     86 	}
     87 
     88 	tc_init(&acpi_timecounter);
     89 
     90 	aprint_debug_dev(sc->sc_dev, "%s %d-bit timer\n",
     91 	    acpi_timecounter.tc_name, bits);
     92 
     93 	return 0;
     94 }
     95 
     96 int
     97 acpitimer_detach(void)
     98 {
     99 
    100 	if (!acpitimer_supported())
    101 		return -1;
    102 
    103 	return tc_detach(&acpi_timecounter);
    104 }
    105 
    106 u_int
    107 acpitimer_read_fast(struct timecounter *tc)
    108 {
    109 	uint32_t t;
    110 
    111 	(void)AcpiGetTimer(&t);
    112 
    113 	return t;
    114 }
    115 
    116 /*
    117  * Some chipsets (PIIX4 variants) do not latch correctly;
    118  * there is a chance that a transition is hit.
    119  */
    120 u_int
    121 acpitimer_read_safe(struct timecounter *tc)
    122 {
    123 	uint32_t t1, t2, t3;
    124 
    125 	(void)AcpiGetTimer(&t2);
    126 	(void)AcpiGetTimer(&t3);
    127 
    128 	do {
    129 		t1 = t2;
    130 		t2 = t3;
    131 
    132 		(void)AcpiGetTimer(&t3);
    133 
    134 	} while ((t1 > t2) || (t2 > t3));
    135 
    136 	return t2;
    137 }
    138 
    139 uint32_t
    140 acpitimer_delta(uint32_t end, uint32_t start)
    141 {
    142 	const u_int mask = acpi_timecounter.tc_counter_mask;
    143 	uint32_t delta;
    144 
    145 	if (end >= start)
    146 		delta = end - start;
    147 	else
    148 		delta = ((mask - start) + end + 1) & mask;
    149 
    150 	return delta;
    151 }
    152 
    153 #define N 2000
    154 
    155 static int
    156 acpitimer_test(void)
    157 {
    158 	uint32_t last, this, delta;
    159 	int minl, maxl, n;
    160 
    161 	minl = 10000000;
    162 	maxl = 0;
    163 
    164 	acpi_md_OsDisableInterrupt();
    165 
    166 	(void)AcpiGetTimer(&last);
    167 
    168 	for (n = 0; n < N; n++) {
    169 
    170 		(void)AcpiGetTimer(&this);
    171 
    172 		delta = acpitimer_delta(this, last);
    173 
    174 		if (delta > maxl)
    175 			maxl = delta;
    176 		else if (delta < minl)
    177 			minl = delta;
    178 
    179 		last = this;
    180 	}
    181 
    182 	acpi_md_OsEnableInterrupt();
    183 
    184 	if (maxl - minl > 2 )
    185 		n = 0;
    186 	else if (minl < 0 || maxl == 0)
    187 		n = 0;
    188 	else
    189 		n = 1;
    190 
    191 	return n;
    192 }
    193