linux/arch/x86/kernel/rtc.c
David P. Reed 04aaa7ba09 x86: fix cmos read and write to not use inb_p and outb_p
fix code to access CMOS rtc registers so that it does not use inb_p and
outb_p routines, which are deprecated.  Extensive research on all known
CMOS RTC chipset timing shows that there is no need for a delay in
accessing the registers of these chips even on old machines. These chipa
are never on an expansion bus, but have always been "motherboard"
resources, either in the processor chipset or explicitly on the
motherboard, and they are not part of the ISA/LPC or PCI buses, so
delays should not be based on bus timing. The reason to fix it:

 1) port 80 writes often hang some laptops that use ENE EC chipsets,
    esp. those designed and manufactured by Quanta for HP;

 2) RTC accesses are timing sensitive, and extra microseconds may matter;

 3) the new "io_delay" function is calibrated by expansion bus timing needs,
    thus is not appropriate for access to CMOS rtc registers.

Signed-off-by: David P. Reed <dpreed@reed.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-04-17 17:40:47 +02:00

199 lines
5.2 KiB
C

/*
* RTC related functions
*/
#include <linux/acpi.h>
#include <linux/bcd.h>
#include <linux/mc146818rtc.h>
#include <asm/time.h>
#include <asm/vsyscall.h>
#ifdef CONFIG_X86_32
/*
* This is a special lock that is owned by the CPU and holds the index
* register we are working with. It is required for NMI access to the
* CMOS/RTC registers. See include/asm-i386/mc146818rtc.h for details.
*/
volatile unsigned long cmos_lock = 0;
EXPORT_SYMBOL(cmos_lock);
#endif
/* For two digit years assume time is always after that */
#define CMOS_YEARS_OFFS 2000
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);
/*
* In order to set the CMOS clock precisely, set_rtc_mmss has to be
* called 500 ms after the second nowtime has started, because when
* nowtime is written into the registers of the CMOS clock, it will
* jump to the next second precisely 500 ms later. Check the Motorola
* MC146818A or Dallas DS12887 data sheet for details.
*
* BUG: This routine does not handle hour overflow properly; it just
* sets the minutes. Usually you'll only notice that after reboot!
*/
int mach_set_rtc_mmss(unsigned long nowtime)
{
int retval = 0;
int real_seconds, real_minutes, cmos_minutes;
unsigned char save_control, save_freq_select;
/* tell the clock it's being set */
save_control = CMOS_READ(RTC_CONTROL);
CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
/* stop and reset prescaler */
save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
cmos_minutes = CMOS_READ(RTC_MINUTES);
if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
BCD_TO_BIN(cmos_minutes);
/*
* since we're only adjusting minutes and seconds,
* don't interfere with hour overflow. This avoids
* messing with unknown time zones but requires your
* RTC not to be off by more than 15 minutes
*/
real_seconds = nowtime % 60;
real_minutes = nowtime / 60;
/* correct for half hour time zone */
if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
real_minutes += 30;
real_minutes %= 60;
if (abs(real_minutes - cmos_minutes) < 30) {
if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
BIN_TO_BCD(real_seconds);
BIN_TO_BCD(real_minutes);
}
CMOS_WRITE(real_seconds,RTC_SECONDS);
CMOS_WRITE(real_minutes,RTC_MINUTES);
} else {
printk(KERN_WARNING
"set_rtc_mmss: can't update from %d to %d\n",
cmos_minutes, real_minutes);
retval = -1;
}
/* The following flags have to be released exactly in this order,
* otherwise the DS12887 (popular MC146818A clone with integrated
* battery and quartz) will not reset the oscillator and will not
* update precisely 500 ms later. You won't find this mentioned in
* the Dallas Semiconductor data sheets, but who believes data
* sheets anyway ... -- Markus Kuhn
*/
CMOS_WRITE(save_control, RTC_CONTROL);
CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
return retval;
}
unsigned long mach_get_cmos_time(void)
{
unsigned int status, year, mon, day, hour, min, sec, century = 0;
/*
* If UIP is clear, then we have >= 244 microseconds before
* RTC registers will be updated. Spec sheet says that this
* is the reliable way to read RTC - registers. If UIP is set
* then the register access might be invalid.
*/
while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
cpu_relax();
sec = CMOS_READ(RTC_SECONDS);
min = CMOS_READ(RTC_MINUTES);
hour = CMOS_READ(RTC_HOURS);
day = CMOS_READ(RTC_DAY_OF_MONTH);
mon = CMOS_READ(RTC_MONTH);
year = CMOS_READ(RTC_YEAR);
#ifdef CONFIG_ACPI
if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
acpi_gbl_FADT.century)
century = CMOS_READ(acpi_gbl_FADT.century);
#endif
status = CMOS_READ(RTC_CONTROL);
WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
BCD_TO_BIN(sec);
BCD_TO_BIN(min);
BCD_TO_BIN(hour);
BCD_TO_BIN(day);
BCD_TO_BIN(mon);
BCD_TO_BIN(year);
}
if (century) {
BCD_TO_BIN(century);
year += century * 100;
printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
} else
year += CMOS_YEARS_OFFS;
return mktime(year, mon, day, hour, min, sec);
}
/* Routines for accessing the CMOS RAM/RTC. */
unsigned char rtc_cmos_read(unsigned char addr)
{
unsigned char val;
lock_cmos_prefix(addr);
outb(addr, RTC_PORT(0));
val = inb(RTC_PORT(1));
lock_cmos_suffix(addr);
return val;
}
EXPORT_SYMBOL(rtc_cmos_read);
void rtc_cmos_write(unsigned char val, unsigned char addr)
{
lock_cmos_prefix(addr);
outb(addr, RTC_PORT(0));
outb(val, RTC_PORT(1));
lock_cmos_suffix(addr);
}
EXPORT_SYMBOL(rtc_cmos_write);
static int set_rtc_mmss(unsigned long nowtime)
{
int retval;
unsigned long flags;
spin_lock_irqsave(&rtc_lock, flags);
retval = set_wallclock(nowtime);
spin_unlock_irqrestore(&rtc_lock, flags);
return retval;
}
/* not static: needed by APM */
unsigned long read_persistent_clock(void)
{
unsigned long retval, flags;
spin_lock_irqsave(&rtc_lock, flags);
retval = get_wallclock();
spin_unlock_irqrestore(&rtc_lock, flags);
return retval;
}
int update_persistent_clock(struct timespec now)
{
return set_rtc_mmss(now.tv_sec);
}
unsigned long long native_read_tsc(void)
{
return __native_read_tsc();
}
EXPORT_SYMBOL(native_read_tsc);