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rtc: Force negative edge on SET after battery replacement

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After the RTC coin cell has been replaced, the Update Cycle Inhibit
bit must see at least one low transition to ensure the RTC counts.
The reset value for this bit is undefined. Examples have been observed
where batteries are installed on a manufacturing line, the bit's state
comes up low, but the RTC does not count.

Change-Id: I05f61efdf941297fa9ec90136124b0c8fe0639c6
Signed-off-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-on: https://review.coreboot.org/17370
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
This commit is contained in:
Marshall Dawson 2016-11-05 18:47:51 -06:00 committed by Martin Roth
parent 5a043fe08d
commit f8a274acf5
1 changed files with 8 additions and 5 deletions
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13
src/drivers/pc80/rtc/mc146818rtc.c
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@ -95,7 +95,7 @@ static void cmos_set_checksum(int range_start, int range_end, int cks_loc)
#ifndef __SMM__
void cmos_init(bool invalid)
{
bool cmos_invalid = invalid;
bool cmos_invalid;
bool checksum_invalid = false;
bool clear_cmos;
size_t i;
@ -114,11 +114,11 @@ void cmos_init(bool invalid)
printk(BIOS_DEBUG, "RTC Init\n");
if (IS_ENABLED(CONFIG_USE_OPTION_TABLE)) {
/* See if there has been a CMOS power problem. */
x = cmos_read(RTC_VALID);
cmos_invalid = !(x & RTC_VRT);
/* See if there has been a CMOS power problem. */
x = cmos_read(RTC_VALID);
cmos_invalid = !(x & RTC_VRT);
if (IS_ENABLED(CONFIG_USE_OPTION_TABLE)) {
/* See if there is a CMOS checksum error */
checksum_invalid = !cmos_checksum_valid(PC_CKS_RANGE_START,
PC_CKS_RANGE_END, PC_CKS_LOC);
@ -128,6 +128,9 @@ void cmos_init(bool invalid)
clear_cmos = true;
}
if (cmos_invalid || invalid)
cmos_write(cmos_read(RTC_CONTROL) | RTC_SET, RTC_CONTROL);
if (invalid || cmos_invalid || checksum_invalid) {
if (clear_cmos) {
cmos_write(0, 0x01);