2 files changed, 37 insertions, 3 deletions
diff --git a/src/mainboard/google/gru/Makefile.inc b/src/mainboard/google/gru/Makefile.inc
index da615132a8..a209d1bdf3 100644
--- a/src/mainboard/google/gru/Makefile.inc
+++ b/src/mainboard/google/gru/Makefile.inc
@@ -13,16 +13,13 @@
 ## GNU General Public License for more details.
 ##
 
-bootblock-y += boardid.c
 bootblock-y += bootblock.c
 bootblock-y += chromeos.c
 bootblock-y += memlayout.ld
 bootblock-y += reset.c
 
-verstage-y += boardid.c
 verstage-y += chromeos.c
 verstage-y += memlayout.ld
-verstage-y += memlayout.ld
 verstage-y += reset.c
 
 romstage-y += boardid.c
diff --git a/src/mainboard/google/gru/boardid.c b/src/mainboard/google/gru/boardid.c
index f62fe97226..5f030adf01 100644
--- a/src/mainboard/google/gru/boardid.c
+++ b/src/mainboard/google/gru/boardid.c
@@ -16,9 +16,46 @@
 #include <boardid.h>
 #include <console/console.h>
 #include <stdlib.h>
+#include <soc/saradc.h>
+
+/*
+ * This matches two Kevin prototypes, needs to be sorted out with HW engs to
+ * have more regular mapping between the voltage and board ID.
+ */
+static const int board_id_readings[] = { 42, 120 };
+
+/*
+ * The ADC produces a 10 bit value, the resistor accuracy is 1%, let's leave
+ * 2% room for error on both sides, total variation would be 4%, which is
+ * approximately 40 points with a 10 bit ADC. The hardware specification
+ * guarantees valid readings to be at least 64 bits (2^6) apart.
+ */
+#define ACCEPTABLE_DELTA  (int)(1024 * .02)
 
 uint8_t board_id(void)
 {
+	static int cached_board_id = -1;
+	int i;
+	int adc_reading;
+
+	if (cached_board_id != -1)
+		return cached_board_id;
+
+	adc_reading = get_saradc_value(1);
+	for (i = 0; i < ARRAY_SIZE(board_id_readings); i++) {
+		int delta = board_id_readings[i] - adc_reading;
+
+		if ((delta < ACCEPTABLE_DELTA) && (delta > -ACCEPTABLE_DELTA)) {
+			printk(BIOS_DEBUG, "ADC reading %d, "
+			       "expected value %d board ID %d\n",
+			       adc_reading, delta + adc_reading, i);
+			cached_board_id = i;
+			return i;
+		}
+	}
+
+	printk(BIOS_ERR, "Unmatched ADC reading of %d, using Board ID of 0\n",
+	       adc_reading);
 	return 0;
 }