mp_clock.c revision 121480 
1/*-
2 * ----------------------------------------------------------------------------
3 * "THE BEER-WARE LICENSE" (Revision 42):
4 * <phk@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
5 * can do whatever you want with this stuff. If we meet some day, and you think
6 * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
7 * ----------------------------------------------------------------------------
8 */
9
10#include <sys/cdefs.h>
11__FBSDID("$FreeBSD: head/sys/i386/i386/mp_clock.c 121480 2003-10-24 21:01:31Z jhb $");
12
13/*-
14 * Just when we thought life were beautiful, reality pops its grim face over
15 * the edge again:
16 *
17 * ] 20. ACPI Timer Errata
18 * ]
19 * ]   Problem: The power management timer may return improper result when
20 * ]   read. Although the timer value settles properly after incrementing,
21 * ]   while incrementing there is a 3nS window every 69.8nS where the
22 * ]   timer value is indeterminate (a 4.2% chance that the data will be
23 * ]   incorrect when read). As a result, the ACPI free running count up
24 * ]   timer specification is violated due to erroneous reads.  Implication:
25 * ]   System hangs due to the "inaccuracy" of the timer when used by
26 * ]   software for time critical events and delays.
27 * ]
28 * ] Workaround: Read the register twice and compare.
29 * ] Status: This will not be fixed in the PIIX4 or PIIX4E.
30 *
31 * The counter is in other words not latched to the PCI bus clock when
32 * read.  Notice the workaround isn't:  We need to read until we have
33 * three monotonic samples and then use the middle one, otherwise we are
34 * not protected against the fact that the bits can be wrong in two
35 * directions.  If we only cared about monosity two reads would be enough.
36 */
37
38/* #include "opt_bus.h" */
39
40#include <sys/param.h>
41#include <sys/systm.h>
42#include <sys/timetc.h>
43#include <sys/kernel.h>
44#include <sys/sysctl.h>
45#include <sys/bus.h>
46
47#include <dev/pci/pcireg.h>
48#include <dev/pci/pcivar.h>
49
50static unsigned piix_get_timecount(struct timecounter *tc);
51
52static u_int32_t piix_timecounter_address;
53static u_int piix_freq = 14318182/4;
54
55static struct timecounter piix_timecounter = {
56	piix_get_timecount,	/* get_timecount */
57	0,			/* no poll_pps */
58	0xffffff,		/* counter_mask */
59	0,			/* frequency */
60	"PIIX"			/* name */
61};
62
63
64static int
65sysctl_machdep_piix_freq(SYSCTL_HANDLER_ARGS)
66{
67	int error;
68	u_int freq;
69
70	if (piix_timecounter.tc_frequency == 0)
71		return (EOPNOTSUPP);
72	freq = piix_freq;
73	error = sysctl_handle_int(oidp, &freq, sizeof(freq), req);
74	if (error == 0 && req->newptr != NULL) {
75		piix_freq = freq;
76		piix_timecounter.tc_frequency = piix_freq;
77	}
78	return (error);
79}
80
81SYSCTL_PROC(_machdep, OID_AUTO, piix_freq, CTLTYPE_INT | CTLFLAG_RW,
82    0, sizeof(u_int), sysctl_machdep_piix_freq, "I", "");
83
84static unsigned
85piix_get_timecount(struct timecounter *tc)
86{
87	unsigned u1, u2, u3;
88
89	u2 = inl(piix_timecounter_address);
90	u3 = inl(piix_timecounter_address);
91	do {
92		u1 = u2;
93		u2 = u3;
94		u3 = inl(piix_timecounter_address);
95	} while (u1 > u2 || u2 > u3);
96	return (u2);
97}
98
99static int
100piix_probe(device_t dev)
101{
102	u_int32_t d;
103
104	if (devclass_get_device(devclass_find("acpi"), 0) != NULL)
105		return (ENXIO);
106	switch (pci_get_devid(dev)) {
107	case 0x71138086:
108		device_set_desc(dev, "PIIX Timecounter");
109		break;
110	default:
111		return (ENXIO);
112	}
113
114	d = pci_read_config(dev, PCIR_COMMAND, 2);
115	if (!(d & PCIM_CMD_PORTEN)) {
116		device_printf(dev, "PIIX I/O space not mapped\n");
117		return (ENXIO);
118	}
119	return (0);
120}
121
122static int
123piix_attach(device_t dev)
124{
125	u_int32_t d;
126
127	d = pci_read_config(dev, 0x40, 4);
128	piix_timecounter_address = (d & 0xffc0) + 8;
129	piix_timecounter.tc_frequency = piix_freq;
130	tc_init(&piix_timecounter);
131	return (0);
132}
133
134static device_method_t piix_methods[] = {
135	/* Device interface */
136	DEVMETHOD(device_probe,		piix_probe),
137	DEVMETHOD(device_attach,	piix_attach),
138	{ 0, 0 }
139};
140
141static driver_t piix_driver = {
142	"piix",
143	piix_methods,
144	1,
145};
146
147static devclass_t piix_devclass;
148
149DRIVER_MODULE(piix, pci, piix_driver, piix_devclass, 0, 0);
150