blob: 628d5429f5e6f977df2a15475b3e104faef8857e [file] [log] [blame]
// Support for MC146818 Real Time Clock chip.
//
// Copyright (C) 2008-2013 Kevin O'Connor <kevin@koconnor.net>
// Copyright (C) 2002 MandrakeSoft S.A.
//
// This file may be distributed under the terms of the GNU LGPLv3 license.
#include "biosvar.h" // GET_LOW
#include "rtc.h" // rtc_read
#include "stacks.h" // yield
#include "util.h" // timer_calc
#include "x86.h" // inb
u8
rtc_read(u8 index)
{
index |= NMI_DISABLE_BIT;
outb(index, PORT_CMOS_INDEX);
return inb(PORT_CMOS_DATA);
}
void
rtc_write(u8 index, u8 val)
{
index |= NMI_DISABLE_BIT;
outb(index, PORT_CMOS_INDEX);
outb(val, PORT_CMOS_DATA);
}
void
rtc_mask(u8 index, u8 off, u8 on)
{
outb(index, PORT_CMOS_INDEX);
u8 val = inb(PORT_CMOS_DATA);
outb((val & ~off) | on, PORT_CMOS_DATA);
}
int
rtc_updating(void)
{
// This function checks to see if the update-in-progress bit
// is set in CMOS Status Register A. If not, it returns 0.
// If it is set, it tries to wait until there is a transition
// to 0, and will return 0 if such a transition occurs. A -1
// is returned only after timing out. The maximum period
// that this bit should be set is constrained to (1984+244)
// useconds, but we wait for longer just to be sure.
if ((rtc_read(CMOS_STATUS_A) & RTC_A_UIP) == 0)
return 0;
u32 end = timer_calc(15);
for (;;) {
if ((rtc_read(CMOS_STATUS_A) & RTC_A_UIP) == 0)
return 0;
if (timer_check(end))
// update-in-progress never transitioned to 0
return -1;
yield();
}
}
void
rtc_setup(void)
{
rtc_write(CMOS_STATUS_A, 0x26); // 32,768Khz src, 976.5625us updates
rtc_mask(CMOS_STATUS_B, ~RTC_B_DSE, RTC_B_24HR);
rtc_read(CMOS_STATUS_C);
rtc_read(CMOS_STATUS_D);
}
int RTCusers VARLOW;
void
rtc_use(void)
{
int count = GET_LOW(RTCusers);
SET_LOW(RTCusers, count+1);
if (count)
return;
// Turn on the Periodic Interrupt timer
rtc_mask(CMOS_STATUS_B, 0, RTC_B_PIE);
}
void
rtc_release(void)
{
int count = GET_LOW(RTCusers);
SET_LOW(RTCusers, count-1);
if (count != 1)
return;
// Clear the Periodic Interrupt.
rtc_mask(CMOS_STATUS_B, RTC_B_PIE, 0);
}