storm: Add board ID calculation function

storm uses three GPIOs in tertiary mode, such that proto0 returns
value of 8 when the GPIOs are interpreted as a single tertiary number.

Adjust the calculated value to return board ID of 0 on proto0, and
monotonously incrementing values on newer boards.

BUG=chrome-os-partner:30489
TEST=when enabled, the board ID value of zero is reported on the console.

Original-Change-Id: I2ff8fd5cbc8d568877b6f8bf220e146893f1e4be
Original-Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/210118
(cherry picked from commit 6ba24f31583933f02be111c8767ae9df56537011)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I35ee218df35a0924d4bb8fcbc6c875450a609f24
Reviewed-on: http://review.coreboot.org/8721
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

2 files changed, 52 insertions, 1 deletions

diff --git a/src/mainboard/google/storm/Makefile.inc b/src/mainboard/google/storm/Makefile.inc
index 4a47c9ec85..907638a3ef 100644
--- a/src/mainboard/google/storm/Makefile.inc
+++ b/src/mainboard/google/storm/Makefile.inc
@@ -22,5 +22,6 @@ bootblock-y += cdp.c
 romstage-y += romstage.c
 romstage-y += cdp.c
 
-ramstage-y += mainboard.c
+ramstage-y += boardid.c
 ramstage-y += cdp.c
+ramstage-y += mainboard.c
diff --git a/src/mainboard/google/storm/boardid.c b/src/mainboard/google/storm/boardid.c
new file mode 100644
index 0000000000..7cbb92a701
--- /dev/null
+++ b/src/mainboard/google/storm/boardid.c
@@ -0,0 +1,50 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2014 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdlib.h>
+#include <boardid.h>
+#include <gpiolib.h>
+#include <console/console.h>
+
+/*
+ * Storm boards dedicate to the board ID three GPIOs in tertiary mode: 29, 30
+ * and 68. On proto0 GPIO68 is used and tied low, so it reads as 'zero' by
+ * gpio_board_id(), whereas the other two pins are not connected and read as
+ * 'two'. This results in gpio_board_id() returning 8 on proto0.
+ *
+ * Three tertitiary signals could represent 27 different values. To make
+ * calculated board ID value continuous and starting at zero, offset the
+ * calculated value by 19 (i.e. 27 - 8) and return modulo 27 of the offset
+ * number. This results in proto0 returning zero as the board ID, the future
+ * revisions will have the inputs configured to match the actual board
+ * revision.
+ */
+
+uint8_t board_id(void)
+{
+	uint8_t bid;
+	gpio_t hw_rev_gpios[] = {68, 30, 29};
+	int offset = 19;
+
+	bid = gpio_board_id(hw_rev_gpios, ARRAY_SIZE(hw_rev_gpios), 1);
+	bid = (bid + offset) % 27;
+	printk(BIOS_INFO, "Board ID %d\n", bid);
+
+	return bid;
+}