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
|
/*
* Copyright (c) 2023 Ian Marco Moffett and the Osmora Team.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Hyra nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <machine/isa/i8254.h>
#include <machine/io.h>
#include <sys/types.h>
#include <sys/cdefs.h>
/*
* Fetches the current count.
*/
uint16_t
i8254_get_count(void)
{
uint8_t lo, hi;
outb(i8254_COMMAND, 0x00);
lo = inb(0x40);
hi = inb(0x40);
return __COMBINE8(hi, lo);
}
/*
* Set the reload value
*
* The reload value is where the i8254's counter
* starts...
*/
void
i8254_set_reload(uint16_t val)
{
/* Channel 0, lo/hi access, rate generator */
outb(i8254_COMMAND, 0x34);
outb(0x40, (val & 0xFF));
outb(0x40, (val >> 8) & 0xFF);
}
void
i8254_set_frequency(uint64_t freq_hz)
{
uint64_t divisor = i8254_DIVIDEND / freq_hz;
if ((i8254_DIVIDEND % freq_hz) > (freq_hz / 2)) {
++divisor;
}
i8254_set_reload(freq_hz);
}
|
