kernel/rtc.c

   1 #include "rtc.h"
   2 #include "stdlib.h"
   3 #include "console.h"
   4 #include "interrupt.h"
   5 #include "portio.h"
   6
   7 static uint8_t read_cmos(const uint8_t reg)
   8 {
   9     /* we don't to cause any undefined behaviour by reading above CMOS RAM */
  10     if(reg >= 64){return 0;}
  11
  12     outb(0x70, reg);
  13     return inb(0x71);
  14 }
  15
  16 static void write_cmos(uint8_t reg, uint8_t val)
  17 {
  18     /* we don't to cause any undefined behaviour by reading above CMOS RAM */
  19     if(reg >= 64){return;}
  20
  21     outb(0x70, reg);
  22     outb(0x71, val);
  23 }
  24
  25 static uint16_t cmos_checksum()
  26 {
  27     uint8_t i;
  28     uint16_t checksum;
  29
  30     checksum = 0;
  31
  32     for(i = 16; i < 46; i++)
  33     {checksum += read_cmos(i);}
  34
  35     return hs2net_16(checksum);
  36 }
  37
  38 static void rtc_handler(int vector, struct interrupt_stack *is)
  39 {
  40     time.second = bcd2bin(read_cmos(0x00));
  41     time.minute = bcd2bin(read_cmos(0x02));
  42     time.hour =  bcd2bin(read_cmos(0x04));
  43     time.day_of_week = bcd2bin(read_cmos(0x06));
  44     time.day_of_month = bcd2bin(read_cmos(0x07));
  45     time.month = bcd2bin(read_cmos(0x08));
  46
  47     uint8_t year = bcd2bin(read_cmos(0x09));
  48     uint16_t century = bcd2bin(read_cmos(0x32));
  49
  50     century *= 100;
  51     time.year = century + year;
  52
  53     read_cmos(0x0C);        /* clear pending interrupts */
  54     ack_irq(8);
  55 }
  56
  57 static void force_update()
  58 {
  59     read_cmos(0x0C);        /* clear pending interrupts */
  60
  61     time.second = bcd2bin(read_cmos(0x00));
  62     time.minute = bcd2bin(read_cmos(0x02));
  63     time.hour =  bcd2bin(read_cmos(0x04));
  64     time.day_of_week = bcd2bin(read_cmos(0x06));
  65     time.day_of_month = bcd2bin(read_cmos(0x07));
  66     time.month = bcd2bin(read_cmos(0x08));
  67
  68     uint8_t year = bcd2bin(read_cmos(0x09));
  69     uint16_t century = bcd2bin(read_cmos(0x32));
  70
  71     century *= 100;
  72     time.year = century + year;
  73 }
  74
  75 void init_rtc()
  76 {
  77     uint8_t status_b;
  78     uint16_t theirs, ours;
  79
  80     theirs = read_cmos(46) & 0xFF;
  81     theirs += ((read_cmos(47) << 8) & 0xFF00);
  82
  83     ours = cmos_checksum();
  84
  85     /* QEMU seems to not use the checksum field, so we have to take this with a grain of salt. */
  86     if(theirs != ours)
  87     {
  88         console_printf(get_vterm(0), "CMOS: checksum error.  theirs = %x, ours = %x \n", theirs, ours);
  89     }
  90
  91     /* this, on the other hand, is not to be looked over lightly */
  92     if(!(read_cmos(0x0D) & 0x80))
  93     {
  94         console_printf(get_vterm(0), "CMOS: data invalid (status register D = %x) \n", read_cmos(0x0D));
  95         return;
  96     }
  97
  98     status_b = read_cmos(0x0B);
  99     status_b |= 0x12;   /* set UI and 24h */
 100     status_b &= 0x9F;   /* clear PI and AI */
 101     write_cmos(0x0B, status_b);
 102
 103     time.second = 0;
 104     interrupt_set_handler(irq_to_int(8), &rtc_handler);
 105     unmask_irq(8);
 106
 107     read_cmos(0x0C);        /* clear pending interrupts */
 108     force_update();
 109
 110     console_printf(get_vterm(0), "RTC: current time = %u:%u:%u, date = %u/%u/%u\n", time.hour, time.minute, time.second, time.month, time.day_of_month, time.year);
 111 }
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