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 * Just when we thought life were beautiful, reality pops its grim face over
10 * the edge again:
11 *
12 * ] 20. ACPI Timer Errata
13 * ]
14 * ] Problem: The power management timer may return improper result when
15 * ] read. Although the timer value settles properly after incrementing,
16 * ] while incrementing there is a 3nS window every 69.8nS where the
17 * ] timer value is indeterminate (a 4.2% chance that the data will be
18 * ] incorrect when read). As a result, the ACPI free running count up
19 * ] timer specification is violated due to erroneous reads. Implication:
20 * ] System hangs due to the "inaccuracy" of the timer when used by
21 * ] software for time critical events and delays.
22 * ]
23 * ] Workaround: Read the register twice and compare.
24 * ] Status: This will not be fixed in the PIIX4 or PIIX4E.
25 *
26 * The counter is in other words not latched to the PCI bus clock when
27 * read. Notice the workaround isn't: We need to read until we have
28 * three monotonic samples and then use the middle one, otherwise we are
29 * not protected against the fact that the bits can be wrong in two
30 * directions. If we only cared about monosity two reads would be enough.
31 *
32 * $FreeBSD: releng/5.0/sys/i386/i386/mp_clock.c 106865 2002-11-13 17:50:59Z mux $
33 *
34 */
35
36 /* #include "opt_bus.h" */
37
38 #include <sys/param.h>
39 #include <sys/systm.h>
40 #include <sys/timetc.h>
41 #include <sys/kernel.h>
42 #include <sys/sysctl.h>
43 #include <sys/bus.h>
44
45 #include <pci/pcivar.h>
46
47 static unsigned piix_get_timecount(struct timecounter *tc);
48
49 static u_int32_t piix_timecounter_address;
50 static u_int piix_freq = 14318182/4;
51
52 static struct timecounter piix_timecounter = {
53 piix_get_timecount,
54 0,
55 0xffffff,
56 0,
57 "PIIX"
58 };
59
60
61 static int
62 sysctl_machdep_piix_freq(SYSCTL_HANDLER_ARGS)
63 {
64 int error;
65 u_int freq;
66
67 if (piix_timecounter.tc_frequency == 0)
68 return (EOPNOTSUPP);
69 freq = piix_freq;
70 error = sysctl_handle_int(oidp, &freq, sizeof(freq), req);
71 if (error == 0 && req->newptr != NULL) {
72 piix_freq = freq;
73 piix_timecounter.tc_frequency = piix_freq;
74 }
75 return (error);
76 }
77
78 SYSCTL_PROC(_machdep, OID_AUTO, piix_freq, CTLTYPE_INT | CTLFLAG_RW,
79 0, sizeof(u_int), sysctl_machdep_piix_freq, "I", "");
80
81 static unsigned
82 piix_get_timecount(struct timecounter *tc)
83 {
84 unsigned u1, u2, u3;
85
86 u2 = inl(piix_timecounter_address);
87 u3 = inl(piix_timecounter_address);
88 do {
89 u1 = u2;
90 u2 = u3;
91 u3 = inl(piix_timecounter_address);
92 } while (u1 > u2 || u2 > u3);
93 return (u2);
94 }
95
96 static int
97 piix_probe (device_t dev)
98 {
99 u_int32_t d;
100
101 switch (pci_get_devid(dev)) {
102 case 0x71138086:
103 d = pci_read_config(dev, 0x4, 2);
104 if (!(d & 1))
105 return 0; /* IO space not mapped */
106 d = pci_read_config(dev, 0x40, 4);
107 piix_timecounter_address = (d & 0xffc0) + 8;
108 piix_timecounter.tc_frequency = piix_freq;
109 tc_init(&piix_timecounter);
110 return (ENXIO);
111 };
112 return (ENXIO);
113 }
114
115 static int
116 piix_attach (device_t dev)
117 {
118
119 return 0;
120 }
121
122 static device_method_t piix_methods[] = {
123 /* Device interface */
124 DEVMETHOD(device_probe, piix_probe),
125 DEVMETHOD(device_attach, piix_attach),
126 { 0, 0 }
127 };
128
129 static driver_t piix_driver = {
130 "piix",
131 piix_methods,
132 1,
133 };
134
135 static devclass_t piix_devclass;
136
137 DRIVER_MODULE(piix, pci, piix_driver, piix_devclass, 0, 0);
Cache object: 9d61e856814396907a20db5d76b2af62
|