rtc: Add an RTC API, and implement it for x86.

This CL adds an API for RTC drivers, and implements its two functions,
rtc_get and rtc_set, for x86's RTC. The function which resets the clock when the
CMOS as lost state now uses the RTC driver instead of accessing the those
registers directly.

BUG=None
TEST=Built and booted on Link with the event log code modified to use
the RTC interface. Verified that the event times were accurate.
BRANCH=nyan

Original-Change-Id: Ifa807898e583254e57167fd44932ea86627a02ee
Original-Signed-off-by: Gabe Black <gabeblack@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/197795
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
Original-Tested-by: Gabe Black <gabeblack@chromium.org>
Original-Commit-Queue: Gabe Black <gabeblack@chromium.org>

This is the first half of the patch.
(cherry picked from commit 9e0fd75142d29afe34f6c6b9ce0099f478ca5a93)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I159f9b4872a0bb932961b4168b180c087dfb1883
Reviewed-on: http://review.coreboot.org/7889
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/drivers/pc80/Kconfig b/src/drivers/pc80/Kconfig
index 5fad3a5433..f8ac5c5a6a 100644
--- a/src/drivers/pc80/Kconfig
+++ b/src/drivers/pc80/Kconfig
@@ -22,3 +22,7 @@ config LPC_TPM
 	  Enable this option to enable TPM support in coreboot.
 
 	  If unsure, say N.
+
+config DRIVERS_MC146818
+	bool
+	default y if ARCH_X86