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: releng/12.0/sys/i386/i386/mp_clock.c 326408 2017-11-30 20:33:45Z pfg $");
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
53 static unsigned piix_get_timecount(struct timecounter *tc);
54
55 static u_int32_t piix_timecounter_address;
56 static u_int piix_freq = 14318182/4;
57
58 static 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
67 static int
68 sysctl_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
84 SYSCTL_PROC(_machdep, OID_AUTO, piix_freq, CTLTYPE_INT | CTLFLAG_RW,
85 0, sizeof(u_int), sysctl_machdep_piix_freq, "I", "");
86
87 static unsigned
88 piix_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
102 static int
103 piix_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
125 static int
126 piix_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
137 static 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
144 static driver_t piix_driver = {
145 "piix",
146 piix_methods,
147 1,
148 };
149
150 static devclass_t piix_devclass;
151
152 DRIVER_MODULE(piix, pci, piix_driver, piix_devclass, 0, 0);
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