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mc146818rtc: disable RTC before writing to nvram 

In principle this isn't necessary. However there's a byte (or several)
outside the first 14 bytes that are part of the RTC, and require
locking (century/altCentury).

Since their location is mostly unknown, guard writes properly.

Change-Id: I847cd4efa92722e8504d29feaf7dbfa5c5244b4e
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/1868
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
This commit is contained in:
Patrick Georgi 2012-11-15 14:54:05 +01:00 committed by Patrick Georgi
parent 4b62ebe961
commit f943901777
1 changed files with 30 additions and 1 deletions
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31
src/include/pc80/mc146818rtc.h
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@ -110,7 +110,7 @@ static inline unsigned char cmos_read(unsigned char addr)
return inb(RTC_BASE_PORT + offs + 1);
}
static inline void cmos_write(unsigned char val, unsigned char addr)
static inline void cmos_write_inner(unsigned char val, unsigned char addr)
{
int offs = 0;
if (addr >= 128) {
@ -121,6 +121,35 @@ static inline void cmos_write(unsigned char val, unsigned char addr)
outb(val, RTC_BASE_PORT + offs + 1);
}
static inline void cmos_write(unsigned char val, unsigned char addr)
{
u8 control_state = cmos_read(RTC_CONTROL);
/* There are various places where RTC bits might be hiding,
* eg. the Century / AltCentury byte. So to be safe, disable
* RTC before changing any value.
*/
if ((addr != RTC_CONTROL) && !(control_state & RTC_SET)) {
cmos_write_inner(control_state | RTC_SET, RTC_CONTROL);
}
cmos_write_inner(val, addr);
/* reset to prior configuration */
if ((addr != RTC_CONTROL) && !(control_state & RTC_SET)) {
cmos_write_inner(control_state, RTC_CONTROL);
}
}
static inline void cmos_disable_rtc(void)
{
u8 control_state = cmos_read(RTC_CONTROL);
cmos_write(control_state | RTC_SET, RTC_CONTROL);
}
static inline void cmos_enable_rtc(void)
{
u8 control_state = cmos_read(RTC_CONTROL);
cmos_write(control_state & ~RTC_SET, RTC_CONTROL);
}
static inline u32 cmos_read32(u8 offset)
{
u32 value = 0;