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 /*-
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/module.h>
45 #include <sys/sysctl.h>
46 #include <sys/bus.h>
47
48 #include <dev/pci/pcireg.h>
49 #include <dev/pci/pcivar.h>
50
51 static unsigned piix_get_timecount(struct timecounter *tc);
52
53 static u_int32_t piix_timecounter_address;
54 static u_int piix_freq = 14318182/4;
55
56 static struct timecounter piix_timecounter = {
57 piix_get_timecount, /* get_timecount */
58 0, /* no poll_pps */
59 0xffffff, /* counter_mask */
60 0, /* frequency */
61 "PIIX" /* name */
62 };
63
64 static int
sysctl_machdep_piix_freq(SYSCTL_HANDLER_ARGS)65 sysctl_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, 0, 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
81 SYSCTL_PROC(_machdep, OID_AUTO, piix_freq,
82 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 0, sizeof(u_int),
83 sysctl_machdep_piix_freq, "I",
84 "");
85
86 static unsigned
piix_get_timecount(struct timecounter * tc)87 piix_get_timecount(struct timecounter *tc)
88 {
89 unsigned u1, u2, u3;
90
91 u2 = inl(piix_timecounter_address);
92 u3 = inl(piix_timecounter_address);
93 do {
94 u1 = u2;
95 u2 = u3;
96 u3 = inl(piix_timecounter_address);
97 } while (u1 > u2 || u2 > u3);
98 return (u2);
99 }
100
101 static int
piix_probe(device_t dev)102 piix_probe(device_t dev)
103 {
104 u_int32_t d;
105
106 if (devclass_get_device(devclass_find("acpi"), 0) != NULL)
107 return (ENXIO);
108 switch (pci_get_devid(dev)) {
109 case 0x71138086:
110 device_set_desc(dev, "PIIX Timecounter");
111 break;
112 default:
113 return (ENXIO);
114 }
115
116 d = pci_read_config(dev, PCIR_COMMAND, 2);
117 if (!(d & PCIM_CMD_PORTEN)) {
118 device_printf(dev, "PIIX I/O space not mapped\n");
119 return (ENXIO);
120 }
121 return (0);
122 }
123
124 static int
piix_attach(device_t dev)125 piix_attach(device_t dev)
126 {
127 u_int32_t d;
128
129 d = pci_read_config(dev, 0x40, 4);
130 piix_timecounter_address = (d & 0xffc0) + 8;
131 piix_timecounter.tc_frequency = piix_freq;
132 tc_init(&piix_timecounter);
133 return (0);
134 }
135
136 static device_method_t piix_methods[] = {
137 /* Device interface */
138 DEVMETHOD(device_probe, piix_probe),
139 DEVMETHOD(device_attach, piix_attach),
140 { 0, 0 }
141 };
142
143 static driver_t piix_driver = {
144 "piix",
145 piix_methods,
146 1,
147 };
148
149 DRIVER_MODULE(piix, pci, piix_driver, 0, 0);
150