nvram: Add option to reset NVRAM to default parameters on every boot

In specific configurations, such as homogeneous supercomputing systems,
changeable NVRAM parameters are more of a liability than a useful tool.
This patch allows a coreboot image to be compiled that will always set
the NVRAM parameters to their default values, reducing maintainance
overhead on large clusters.

Change-Id: Ic03e34211d4a58cd60740f2d9a6b50e11fe85822
Signed-off-by: Timothy Pearson <tpearson@raptorengineeringinc.com>
Reviewed-on: http://review.coreboot.org/8446
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

src/Kconfig

@@ -116,6 +116,15 @@ config USE_OPTION_TABLE
 	  Enable this option if coreboot shall read options from the "CMOS"
 	  NVRAM instead of using hard-coded values.
 
+config STATIC_OPTION_TABLE
+	bool "Load default configuration values into CMOS on each boot"
+	default n
+	depends on USE_OPTION_TABLE
+	help
+	  Enable this option to reset "CMOS" NVRAM values to default on
+	  every boot.  Use this if you want the NVRAM configuration to
+	  never be modified from its default values.
+
 config COMPRESS_RAMSTAGE
 	bool "Compress ramstage with LZMA"
 	default y

src/arch/x86/include/bootblock_common.h

@@ -32,7 +32,7 @@ static void bootblock_mainboard_init(void)
 #if CONFIG_USE_OPTION_TABLE
 static void sanitize_cmos(void)
 {
-	if (cmos_error() || !cmos_chksum_valid()) {
+	if (cmos_error() || !cmos_chksum_valid() || IS_ENABLED(CONFIG_STATIC_OPTION_TABLE)) {
 		unsigned char *cmos_default = (unsigned char*)walkcbfs("cmos.default");
 		if (cmos_default) {
 			int i;

src/drivers/pc80/mc146818rtc.c

@@ -56,6 +56,9 @@ static void cmos_reset_date(void)
 
 static int cmos_checksum_valid(int range_start, int range_end, int cks_loc)
 {
+	if (IS_ENABLED(CONFIG_STATIC_OPTION_TABLE))
+		return 1;
+
 	int i;
 	u16 sum, old_sum;
 	sum = 0;