1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
|
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2007 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/* Copyright (c) 1990, 1991 UNIX System Laboratories, Inc. */
/* Copyright (c) 1984, 1986, 1987, 1988, 1989, 1990 AT&T */
/* All Rights Reserved */
#pragma ident "%Z%%M% %I% %E% SMI"
#include <sys/types.h>
#include <sys/dl.h>
#include <sys/param.h>
#include <sys/pit.h>
#include <sys/inline.h>
#include <sys/machlock.h>
#include <sys/avintr.h>
#include <sys/smp_impldefs.h>
#include <sys/archsystm.h>
#include <sys/systm.h>
#include <sys/machsystm.h>
#define PIT_COUNTDOWN (PIT_READMODE | PIT_NDIVMODE)
#define MICROCOUNT 0x2000
/*
* Loop count for 10 microsecond wait. MUST be initialized for those who
* insist on calling "tenmicrosec" before the clock has been initialized.
*/
unsigned int microdata = 50;
void
microfind(void)
{
uint64_t max, count = MICROCOUNT;
/*
* The algorithm tries to guess a loop count for tenmicrosec such
* that found will be 0xf000 PIT counts, but because it is only a
* rough guess there is no guarantee that tenmicrosec will take
* exactly 0xf000 PIT counts. min is set initially to 0xe000 and
* represents the number of PIT counts that must elapse in
* tenmicrosec for microfind to calculate the correct loop count for
* tenmicrosec. The algorith will successively set count to better
* approximations until the number of PIT counts elapsed are greater
* than min. Ideally the first guess should be correct, but as cpu's
* become faster MICROCOUNT may have to be increased to ensure
* that the first guess for count is correct. There is no harm
* leaving MICRCOUNT at 0x2000, the results will be correct, it just
* may take longer to calculate the correct value for the loop
* count used by tenmicrosec. In some cases min may be reset as the
* algorithm progresses in order to facilitate faster cpu's.
*/
unsigned long found, min = 0xe000;
ulong_t s;
unsigned char status;
s = clear_int_flag(); /* disable interrupts */
/*CONSTCOND*/
while (1) {
/*
* microdata is the loop count used in tenmicrosec. The first
* time around microdata is set to 1 to make tenmicrosec
* return quickly. The purpose of this while loop is to
* warm the cache for the next time around when the number
* of PIT counts are measured.
*/
microdata = 1;
/*CONSTCOND*/
while (1) {
/* Put counter 0 in mode 0 */
outb(PITCTL_PORT, PIT_LOADMODE);
/* output a count of -1 to counter 0 */
outb(PITCTR0_PORT, 0xff);
outb(PITCTR0_PORT, 0xff);
tenmicrosec();
/* READ BACK counter 0 to latch status and count */
outb(PITCTL_PORT, PIT_READBACK|PIT_READBACKC0);
/* Read status of counter 0 */
status = inb(PITCTR0_PORT);
/* Read the value left in the counter */
found = inb(PITCTR0_PORT) | (inb(PITCTR0_PORT) << 8);
if (microdata != 1)
break;
microdata = count;
}
/* verify that the counter began the count-down */
if (status & (1 << PITSTAT_NULLCNT)) {
/* microdata is too small */
count = count << 1;
/*
* If the cpu is so fast that it cannot load the
* counting element of the PIT with a very large
* value for the loop used in tenmicrosec, then
* the algorithm will not work for this cpu.
* It is very unlikely there will ever be such
* an x86.
*/
if (count > 0x100000000)
panic("microfind: cpu is too fast");
continue;
}
/* verify that the counter did not wrap around */
if (status & (1 << PITSTAT_OUTPUT)) {
/*
* microdata is too large. Since there are counts
* that would have been appropriate for the PIT
* not to wrap on even a lowly AT, count will never
* decrease to 1.
*/
count = count >> 1;
continue;
}
/* mode 0 is an n + 1 counter */
found = 0x10000 - found;
if (found > min)
break;
/* verify that the cpu is slow enough to count to 0xf000 */
count *= 0xf000;
max = 0x100000001 * found;
/*
* It is possible that at some point cpu's will become
* sufficiently fast such that the PIT will not be able to
* count to 0xf000 within the maximum loop count used in
* tenmicrosec. In that case the loop count in tenmicrosec
* may be set to the maximum value because it is unlikely
* that the cpu will be so fast that tenmicrosec with the
* maximum loop count will take more than ten microseconds.
* If the cpu is indeed too fast for the current
* implementation of tenmicrosec, then there is code below
* intended to catch that situation.
*/
if (count >= max) {
/* cpu is fast, just make it count as high it can */
count = 0x100000000;
min = 0;
continue;
}
/*
* Count in the neighborhood of 0xf000 next time around
* There is no risk of dividing by zero since found is in the
* range of 0x1 to 0x1000.
*/
count = count / found;
}
/*
* Formula for delaycount is :
* (loopcount * timer clock speed) / (counter ticks * 1000)
* Note also that 1000 is for figuring out milliseconds
*/
count *= PIT_HZ;
max = ((uint64_t)found) * 100000;
count = count / max; /* max is never zero */
if (count >= 0x100000001)
/*
* This cpu is too fast for the current implementation of
* tenmicrosec. It is unlikely such a fast x86 will exist.
*/
panic("microfind: cpu is too fast");
if (count != 0)
microdata = count;
else
microdata = 1;
/* Restore timer channel 0 for BIOS use */
/* write mode to 3, square-wave */
outb(PITCTL_PORT, PIT_C0 | PIT_LOADMODE | PIT_SQUAREMODE);
/* write 16 bits of 0 for initial count */
outb(PITCTR0_PORT, 0);
outb(PITCTR0_PORT, 0);
restore_int_flag(s); /* restore interrupt state */
}
|
