as3277: Fix month-off-by-one error for RTC driver

The AS3277 RTC code seems to closely follow the corresponding Linux
driver. Unfortunately, while coreboot (and even other parts of Linux,
like mktime()) directly follows the standard IBM PC RTC time
representation (except for the BCD part), Linux' struct rtc_time decided
to use 0-based (instead of 1-based) months instead.

This patch removes the faulty month offset that was copied into our
driver so that we will generate correct timestamps again.

BRANCH=nyan
BUG=chrome-os-partner:34108
TEST=firmware_EventLog (pre-release version) gets further than before
(and then craps up on unrelated problems with suspend/resume events).

Change-Id: Ica221a8bcfd7c1c6cd7ba382d760b586d511e3a3
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 5b55c3f5bbecc776a71338256b910aecccac1e04
Original-Change-Id: I163fa4778ec534cd9e6f92a6b6dc55e9871a6a82
Original-Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/238122
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/9723
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/src/drivers/ams/as3722rtc.c b/src/drivers/ams/as3722rtc.c
index 8fe5748..e15ae32 100644
--- a/src/drivers/ams/as3722rtc.c
+++ b/src/drivers/ams/as3722rtc.c
@@ -72,7 +72,7 @@
 	as3722_write(AS3722_RTC_MINUTE, bin2bcd(time->min));
 	as3722_write(AS3722_RTC_HOUR, bin2bcd(time->hour));
 	as3722_write(AS3722_RTC_DAY, bin2bcd(time->mday));
-	as3722_write(AS3722_RTC_MONTH, bin2bcd(time->mon + 1));
+	as3722_write(AS3722_RTC_MONTH, bin2bcd(time->mon));
 	as3722_write(AS3722_RTC_YEAR, bin2bcd(time->year));
 	return 0;
 }
@@ -85,7 +85,7 @@
 	time->min = bcd2bin(as3722_read(AS3722_RTC_MINUTE) & 0x7f);
 	time->hour = bcd2bin(as3722_read(AS3722_RTC_HOUR) & 0x3f);
 	time->mday = bcd2bin(as3722_read(AS3722_RTC_DAY) & 0x3f);
-	time->mon = bcd2bin(as3722_read(AS3722_RTC_MONTH) & 0x1f) - 1;
+	time->mon = bcd2bin(as3722_read(AS3722_RTC_MONTH) & 0x1f);
 	time->year = bcd2bin(as3722_read(AS3722_RTC_YEAR) & 0x7f);
 	return 0;
 }