1/*-
2 * SPDX-License-Identifier: Beerware
3 *
4 * ----------------------------------------------------------------------------
5 * "THE BEER-WARE LICENSE" (Revision 42):
6 * <phk@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
7 * can do whatever you want with this stuff. If we meet some day, and you think
8 * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
9 * ----------------------------------------------------------------------------
10 */
11
12#include <sys/cdefs.h>
13__FBSDID("$FreeBSD$");
14
15/*-
16 * Just when we thought life were beautiful, reality pops its grim face over
17 * the edge again:
18 *
19 * ] 20. ACPI Timer Errata
20 * ]
21 * ]   Problem: The power management timer may return improper result when
22 * ]   read. Although the timer value settles properly after incrementing,
23 * ]   while incrementing there is a 3nS window every 69.8nS where the
24 * ]   timer value is indeterminate (a 4.2% chance that the data will be
25 * ]   incorrect when read). As a result, the ACPI free running count up
26 * ]   timer specification is violated due to erroneous reads.  Implication:
27 * ]   System hangs due to the "inaccuracy" of the timer when used by
28 * ]   software for time critical events and delays.
29 * ]
30 * ] Workaround: Read the register twice and compare.
31 * ] Status: This will not be fixed in the PIIX4 or PIIX4E.
32 *
33 * The counter is in other words not latched to the PCI bus clock when
34 * read.  Notice the workaround isn't:  We need to read until we have
35 * three monotonic samples and then use the middle one, otherwise we are
36 * not protected against the fact that the bits can be wrong in two
37 * directions.  If we only cared about monosity two reads would be enough.
38 */
39
40/* #include "opt_bus.h" */
41
42#include <sys/param.h>
43#include <sys/systm.h>
44#include <sys/timetc.h>
45#include <sys/kernel.h>
46#include <sys/module.h>
47#include <sys/sysctl.h>
48#include <sys/bus.h>
49
50#include <dev/pci/pcireg.h>
51#include <dev/pci/pcivar.h>
52
53static unsigned piix_get_timecount(struct timecounter *tc);
54
55static u_int32_t piix_timecounter_address;
56static u_int piix_freq = 14318182/4;
57
58static struct timecounter piix_timecounter = {
59	piix_get_timecount,	/* get_timecount */
60	0,			/* no poll_pps */
61	0xffffff,		/* counter_mask */
62	0,			/* frequency */
63	"PIIX"			/* name */
64};
65
66
67static int
68sysctl_machdep_piix_freq(SYSCTL_HANDLER_ARGS)
69{
70	int error;
71	u_int freq;
72
73	if (piix_timecounter.tc_frequency == 0)
74		return (EOPNOTSUPP);
75	freq = piix_freq;
76	error = sysctl_handle_int(oidp, &freq, 0, req);
77	if (error == 0 && req->newptr != NULL) {
78		piix_freq = freq;
79		piix_timecounter.tc_frequency = piix_freq;
80	}
81	return (error);
82}
83
84SYSCTL_PROC(_machdep, OID_AUTO, piix_freq, CTLTYPE_INT | CTLFLAG_RW,
85    0, sizeof(u_int), sysctl_machdep_piix_freq, "I", "");
86
87static unsigned
88piix_get_timecount(struct timecounter *tc)
89{
90	unsigned u1, u2, u3;
91
92	u2 = inl(piix_timecounter_address);
93	u3 = inl(piix_timecounter_address);
94	do {
95		u1 = u2;
96		u2 = u3;
97		u3 = inl(piix_timecounter_address);
98	} while (u1 > u2 || u2 > u3);
99	return (u2);
100}
101
102static int
103piix_probe(device_t dev)
104{
105	u_int32_t d;
106
107	if (devclass_get_device(devclass_find("acpi"), 0) != NULL)
108		return (ENXIO);
109	switch (pci_get_devid(dev)) {
110	case 0x71138086:
111		device_set_desc(dev, "PIIX Timecounter");
112		break;
113	default:
114		return (ENXIO);
115	}
116
117	d = pci_read_config(dev, PCIR_COMMAND, 2);
118	if (!(d & PCIM_CMD_PORTEN)) {
119		device_printf(dev, "PIIX I/O space not mapped\n");
120		return (ENXIO);
121	}
122	return (0);
123}
124
125static int
126piix_attach(device_t dev)
127{
128	u_int32_t d;
129
130	d = pci_read_config(dev, 0x40, 4);
131	piix_timecounter_address = (d & 0xffc0) + 8;
132	piix_timecounter.tc_frequency = piix_freq;
133	tc_init(&piix_timecounter);
134	return (0);
135}
136
137static device_method_t piix_methods[] = {
138	/* Device interface */
139	DEVMETHOD(device_probe,		piix_probe),
140	DEVMETHOD(device_attach,	piix_attach),
141	{ 0, 0 }
142};
143
144static driver_t piix_driver = {
145	"piix",
146	piix_methods,
147	1,
148};
149
150static devclass_t piix_devclass;
151
152DRIVER_MODULE(piix, pci, piix_driver, piix_devclass, 0, 0);
153