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
|
#include <pc80/mc146818rtc.h>
#include <part/fallback_boot.h>
#ifndef MAX_REBOOT_CNT
#error "MAX_REBOOT_CNT not defined"
#endif
#if MAX_REBOOT_CNT > 15
#error "MAX_REBOOT_CNT too high"
#endif
static unsigned char cmos_read(unsigned char addr)
{
outb(addr, RTC_BASE_PORT + 0);
return inb(RTC_BASE_PORT + 1);
}
static void cmos_write(unsigned char val, unsigned char addr)
{
outb(addr, RTC_BASE_PORT + 0);
outb(val, RTC_BASE_PORT + 1);
}
static int cmos_error(void)
{
unsigned char reg_d;
/* See if the cmos error condition has been flagged */
reg_d = cmos_read(RTC_REG_D);
return (reg_d & RTC_VRT) == 0;
}
static int cmos_chksum_valid(void)
{
unsigned char addr;
unsigned long sum, old_sum;
sum = 0;
/* Comput the cmos checksum */
for(addr = LB_CKS_RANGE_START; addr <= LB_CKS_RANGE_END; addr++) {
sum += cmos_read(addr);
}
sum = (sum & 0xffff) ^ 0xffff;
/* Read the stored checksum */
old_sum = cmos_read(LB_CKS_LOC) << 8;
old_sum |= cmos_read(LB_CKS_LOC+1);
return sum == old_sum;
}
static int last_boot_normal(void)
{
unsigned char byte;
byte = cmos_read(RTC_BOOT_BYTE);
return (byte & (1 << 1));
}
static int do_normal_boot(void)
{
unsigned char byte;
if (cmos_error() || !cmos_chksum_valid()) {
unsigned char byte;
/* There are no impossible values, no cheksums so just
* trust whatever value we have in the the cmos,
* but clear the fallback bit.
*/
byte = cmos_read(RTC_BOOT_BYTE);
byte &= 0x0c;
byte |= MAX_REBOOT_CNT << 4;
cmos_write(byte, RTC_BOOT_BYTE);
}
/* The RTC_BOOT_BYTE is now o.k. see where to go. */
byte = cmos_read(RTC_BOOT_BYTE);
/* Are we in normal mode? */
if (byte & 1) {
byte &= 0x0f; /* yes, clear the boot count */
}
/* Properly set the last boot flag */
byte &= 0xfc;
if ((byte >> 4) < MAX_REBOOT_CNT) {
byte |= (1<<1);
}
/* Are we already at the max count? */
if ((byte >> 4) < MAX_REBOOT_CNT) {
byte += 1 << 4; /* No, add 1 to the count */
}
else {
byte &= 0xfc; /* Yes, put in fallback mode */
}
/* Save the boot byte */
cmos_write(byte, RTC_BOOT_BYTE);
return (byte & (1<<1));
}
|
