kernel tree reorganization stage 1: Major cvs repository work (not logged as
[dragonfly.git] / sys / i386 / i386 / mp_clock.c
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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: src/sys/i386/i386/mp_clock.c,v 1.4.2.2 2000/09/30 02:49:32 ps Exp $
1f2de5d4 33 * $DragonFly: src/sys/i386/i386/Attic/mp_clock.c,v 1.3 2003/08/07 21:17:22 dillon Exp $
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34 *
35 */
36
37/* #include "opt_bus.h" */
38/* #include "opt_pci.h" */
39
40#include <sys/param.h>
41#include <sys/systm.h>
42#include <sys/time.h>
43#include <sys/kernel.h>
44#include <sys/sysctl.h>
45#include <sys/bus.h>
46
1f2de5d4 47#include <bus/pci/pcivar.h>
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48
49static unsigned piix_get_timecount(struct timecounter *tc);
50
51static u_int32_t piix_timecounter_address;
52static u_int piix_freq = 14318182/4;
53
54static struct timecounter piix_timecounter = {
55 piix_get_timecount,
56 0,
57 0xffffff,
58 0,
59 "PIIX"
60};
61
62SYSCTL_OPAQUE(_debug, OID_AUTO, piix_timecounter, CTLFLAG_RD,
63 &piix_timecounter, sizeof(piix_timecounter), "S,timecounter", "");
64
65static int
66sysctl_machdep_piix_freq(SYSCTL_HANDLER_ARGS)
67{
68 int error;
69 u_int freq;
70
71 if (piix_timecounter.tc_frequency == 0)
72 return (EOPNOTSUPP);
73 freq = piix_freq;
74 error = sysctl_handle_int(oidp, &freq, sizeof(freq), req);
75 if (error == 0 && req->newptr != NULL) {
76 piix_freq = freq;
77 piix_timecounter.tc_frequency = piix_freq;
78 update_timecounter(&piix_timecounter);
79 }
80 return (error);
81}
82
83SYSCTL_PROC(_machdep, OID_AUTO, piix_freq, CTLTYPE_INT | CTLFLAG_RW,
84 0, sizeof(u_int), sysctl_machdep_piix_freq, "I", "");
85
86static unsigned
87piix_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
101static int
102piix_probe (device_t dev)
103{
104 u_int32_t d;
105
106 switch (pci_get_devid(dev)) {
107 case 0x71138086:
108 d = pci_read_config(dev, 0x4, 2);
109 if (!(d & 1))
110 return 0; /* IO space not mapped */
111 d = pci_read_config(dev, 0x40, 4);
112 piix_timecounter_address = (d & 0xffc0) + 8;
113 piix_timecounter.tc_frequency = piix_freq;
114 init_timecounter(&piix_timecounter);
115 return (ENXIO);
116 };
117 return (ENXIO);
118}
119
120static int
121piix_attach (device_t dev)
122{
123
124 return 0;
125}
126
127static device_method_t piix_methods[] = {
128 /* Device interface */
129 DEVMETHOD(device_probe, piix_probe),
130 DEVMETHOD(device_attach, piix_attach),
131 { 0, 0 }
132};
133
134static driver_t piix_driver = {
135 "piix",
136 piix_methods,
137 1,
138};
139
140static devclass_t piix_devclass;
141
142DRIVER_MODULE(piix, pci, piix_driver, piix_devclass, 0, 0);