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
|
/*
* Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
* You can also choose to distribute this program under the terms of
* the Unmodified Binary Distribution Licence (as given in the file
* COPYING.UBDL), provided that you have satisfied its requirements.
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
/** @file
*
* BIOS timer
*
*/
#include <ipxe/timer.h>
#include <realmode.h>
#include <bios.h>
#include <ipxe/pit8254.h>
/** Number of ticks per day
*
* This seems to be the normative value, as used by e.g. SeaBIOS to
* decide when to set the midnight rollover flag.
*/
#define BIOS_TICKS_PER_DAY 0x1800b0
/** Number of ticks per BIOS tick */
#define TICKS_PER_BIOS_TICK \
( ( TICKS_PER_SEC * 60 * 60 * 24 ) / BIOS_TICKS_PER_DAY )
/**
* Get current system time in ticks
*
* @ret ticks Current time, in ticks
*
* Use direct memory access to BIOS variables, longword 0040:006C
* (ticks today) and byte 0040:0070 (midnight crossover flag) instead
* of calling timeofday BIOS interrupt.
*/
static unsigned long bios_currticks ( void ) {
static uint32_t offset;
uint32_t ticks;
uint8_t midnight;
/* Re-enable interrupts so that the timer interrupt can occur */
__asm__ __volatile__ ( "sti\n\t"
"nop\n\t"
"nop\n\t"
"cli\n\t" );
/* Read current BIOS time of day */
get_real ( ticks, BDA_SEG, BDA_TICKS );
get_real ( midnight, BDA_SEG, BDA_MIDNIGHT );
/* Handle midnight rollover */
if ( midnight ) {
midnight = 0;
put_real ( midnight, BDA_SEG, BDA_MIDNIGHT );
offset += BIOS_TICKS_PER_DAY;
}
ticks += offset;
/* Convert to timer ticks */
return ( ticks * TICKS_PER_BIOS_TICK );
}
/** BIOS timer */
struct timer bios_timer __timer ( TIMER_NORMAL ) = {
.name = "bios",
.currticks = bios_currticks,
.udelay = pit8254_udelay,
};
|
