Generalize revision number calculation function

Some platforms use tertiary interpretation of GPIO input state to
increase number of distinct values represented by a limited number of
GPIOs. The three states are

- external pull down (interpreted as 0)
- external pull up (1)
- not connected (2)

This has been required by Nvidia devices so far, but Exynos and
Ipq8086 platforms need this too.

This patch moves the function reading the tertiary state into the
library and exposes the necessary GPIO API functions in a new include
file. The functions are still supposed to be provided by platform
specific modules.

The function interpreting the GPIO states has been modified to allow
to interpret the state either as a true tertiary number or as a set
two bit fields.

Since linker garbage collection is not happening when building x86
targets, a new configuration option is being added to include the new
module only when needed.

BUG=chrome-os-partner:30489
TEST=verified that nyan_big still reports proper revision ID.

Change-Id: Ib55122c359629b58288c1022da83e6c63dc2264d
Original-Change-Id: I243c9f43c82bd4a41de2154bbdbd07df0a241046
Original-Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/209673
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
(cherry picked from commit c79ef1c545d073eaad69e6c8c629f9656b8c2f3e)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Reviewed-on: http://review.coreboot.org/8717
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

9 files changed, 155 insertions, 90 deletions

diff --git a/src/Kconfig b/src/Kconfig
index 26141fe3a2..25184eb887 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -1122,6 +1122,13 @@ config DEBUG_COVERAGE
 	  If enabled, the code coverage hooks in coreboot will output some
 	  information about the coverage data that is dumped.
 
+config TERTIARY_BOARD_ID
+	bool "Interpret board ID GPIOs as tertiary inputs"
+	default n
+	help
+	  Consider each GPIO as being in one of three states: pulled down (0),
+	  pulled up (1), or not connected (2)
+
 endmenu
 
 # These probably belong somewhere else, but they are needed somewhere.
@@ -1184,4 +1191,4 @@ config MAX_REBOOT_CNT
 	help
 	  Internal option that sets the maximum number of bootblock executions allowed
 	  with the normal image enabled before assuming the normal image is defective
-	  and switching to the fallback image.
\ No newline at end of file
+	  and switching to the fallback image.
diff --git a/src/include/gpiolib.h b/src/include/gpiolib.h
new file mode 100644
index 0000000000..daec3b66bd
--- /dev/null
+++ b/src/include/gpiolib.h
@@ -0,0 +1,47 @@
+/*
+ * 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
+ */
+
+#ifndef __SRC_INCLUDE_GPIOLIB_H__
+#define __SRC_INCLUDE_GPIOLIB_H__
+
+/* A generic type, use accessor macros to actually access the hardware. */
+typedef unsigned gpio_t;
+
+/*
+ * Read the value presented by the set of GPIOs, when each pin is interpreted
+ * as a number in 0..2 range depending on the external pullup situation.
+ *
+ * Depending on the third parameter, the return value is either a set of two
+ * bit fields, each representing one GPIO value, or a number where each GPIO is
+ * included multiplied by 3^gpio_num, resulting in a true tertiary value.
+ *
+ */
+int gpio_board_id(gpio_t gpio[], int num_gpio, int tertiary);
+
+/*
+ * The following functions are not provided by the common library, but must be
+ * implemented by the appropriate SOC/board instead.
+ */
+int gpio_get_in_value(gpio_t gpio);
+void gpio_set_out_value(gpio_t gpio, int value);
+void gpio_input_pulldown(gpio_t gpio);
+void gpio_input_pullup(gpio_t gpio);
+void gpio_input(gpio_t gpio);
+
+#endif
diff --git a/src/lib/Makefile.inc b/src/lib/Makefile.inc
index d1e3a92b21..1e70e2e01a 100644
--- a/src/lib/Makefile.inc
+++ b/src/lib/Makefile.inc
@@ -57,6 +57,7 @@ ifeq ($(CONFIG_COMPILER_GCC),y)
 romstage-$(CONFIG_ARCH_ROMSTAGE_X86_32) += gcc.c
 ramstage-$(CONFIG_ARCH_RAMSTAGE_X86_32) += gcc.c
 endif
+romstage-$(CONFIG_TERTIARY_BOARD_ID) += tristate_gpios.c
 
 ramstage-y += hardwaremain.c
 ramstage-y += selfboot.c
diff --git a/src/lib/tristate_gpios.c b/src/lib/tristate_gpios.c
new file mode 100644
index 0000000000..b1ebbc0f71
--- /dev/null
+++ b/src/lib/tristate_gpios.c
@@ -0,0 +1,79 @@
+/*
+ * 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 <delay.h>
+#include <gpiolib.h>
+
+int gpio_board_id(gpio_t gpio[], int num_gpio, int tertiary)
+{
+	/*
+	 * GPIOs which are tied to stronger external pull up or pull down
+	 * will stay there regardless of the internal pull up or pull
+	 * down setting.
+	 *
+	 * GPIOs which are floating will go to whatever level they're
+	 * internally pulled to.
+	 */
+
+	int temp;
+	int index;
+	int id = 0;
+	char value[num_gpio];
+
+	/* Enable internal pull up */
+	for (index = 0; index < num_gpio; ++index)
+		gpio_input_pullup(gpio[index]);
+
+	/* Wait until signals become stable */
+	udelay(10);
+
+	/* Get gpio values at internal pull up */
+	for (index = 0; index < num_gpio; ++index)
+		value[index] = gpio_get_in_value(gpio[index]);
+
+	/* Enable internal pull down */
+	for (index = 0; index < num_gpio; ++index)
+		gpio_input_pulldown(gpio[index]);
+
+	/* Wait until signals become stable */
+	udelay(10);
+
+	/*
+	 * Get gpio values at internal pull down.
+	 * Compare with gpio pull up value and then
+	 * determine a gpio final value/state:
+	 *  0: pull down
+	 *  1: pull up
+	 *  2: floating
+	 */
+	for (index = 0; index < num_gpio; ++index) {
+		if (tertiary)
+			id *= 3;
+		else
+			id <<= 2;
+		temp = gpio_get_in_value(gpio[index]);
+		id += ((value[index] ^ temp) << 1) | temp;
+	}
+
+	/* Disable pull up / pull down to conserve power */
+	for (index = 0; index < num_gpio; ++index)
+		gpio_input(gpio[index]);
+
+	return id;
+}
diff --git a/src/mainboard/google/nyan_big/boardid.c b/src/mainboard/google/nyan_big/boardid.c
index c7bd2e6a1d..c79af45812 100644
--- a/src/mainboard/google/nyan_big/boardid.c
+++ b/src/mainboard/google/nyan_big/boardid.c
@@ -29,15 +29,9 @@ uint8_t board_id(void)
 
 	if (id < 0) {
 		gpio_t gpio[] = {GPIO(Q3), GPIO(T1), GPIO(X1), GPIO(X4)};
-		int value[ARRAY_SIZE(gpio)];
 
-		gpio_get_in_tristate_values(gpio, ARRAY_SIZE(gpio), value);
+		id = gpio_board_id(gpio, ARRAY_SIZE(gpio), 0);
 
-		/* A gpio state is encoded in every two-bit */
-		id = value[0] << 0 |
-		     value[1] << 2 |
-		     value[2] << 4 |
-		     value[3] << 6;
 		printk(BIOS_SPEW, "Board TRISTATE ID: %#x.\n", id);
 	}
 
diff --git a/src/mainboard/google/nyan_blaze/boardid.c b/src/mainboard/google/nyan_blaze/boardid.c
index c7bd2e6a1d..c79af45812 100644
--- a/src/mainboard/google/nyan_blaze/boardid.c
+++ b/src/mainboard/google/nyan_blaze/boardid.c
@@ -29,15 +29,9 @@ uint8_t board_id(void)
 
 	if (id < 0) {
 		gpio_t gpio[] = {GPIO(Q3), GPIO(T1), GPIO(X1), GPIO(X4)};
-		int value[ARRAY_SIZE(gpio)];
 
-		gpio_get_in_tristate_values(gpio, ARRAY_SIZE(gpio), value);
+		id = gpio_board_id(gpio, ARRAY_SIZE(gpio), 0);
 
-		/* A gpio state is encoded in every two-bit */
-		id = value[0] << 0 |
-		     value[1] << 2 |
-		     value[2] << 4 |
-		     value[3] << 6;
 		printk(BIOS_SPEW, "Board TRISTATE ID: %#x.\n", id);
 	}
 
diff --git a/src/soc/nvidia/tegra/gpio.c b/src/soc/nvidia/tegra/gpio.c
index b10cded12d..17b90aa1d9 100644
--- a/src/soc/nvidia/tegra/gpio.c
+++ b/src/soc/nvidia/tegra/gpio.c
@@ -23,6 +23,7 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <delay.h>
+#include <gpiolib.h>
 
 #include "gpio.h"
 #include "pinmux.h"
@@ -175,58 +176,6 @@ int gpio_get_in_value(gpio_t gpio)
 	return (port & (1 << bit)) != 0;
 }
 
-int gpio_get_in_tristate_values(gpio_t gpio[], int num_gpio, int value[])
-{
-	/*
-	 * GPIOs which are tied to stronger external pull up or pull down
-	 * will stay there regardless of the internal pull up or pull
-	 * down setting.
-	 *
-	 * GPIOs which are floating will go to whatever level they're
-	 * internally pulled to.
-	 */
-
-	int temp;
-	int index;
-
-	/* Enable internal pull up */
-	for (index = 0; index < num_gpio; ++index)
-		gpio_input_pullup(gpio[index]);
-
-	/* Wait until signals become stable */
-	udelay(10);
-
-	/* Get gpio values at internal pull up */
-	for (index = 0; index < num_gpio; ++index)
-		value[index] = gpio_get_in_value(gpio[index]);
-
-	/* Enable internal pull down */
-	for (index = 0; index < num_gpio; ++index)
-		gpio_input_pulldown(gpio[index]);
-
-	/* Wait until signals become stable */
-	udelay(10);
-
-	/*
-	 * Get gpio values at internal pull down.
-	 * Compare with gpio pull up value and then
-	 * determine a gpio final value/state:
-	 *  0: pull down
-	 *  1: pull up
-	 *  2: floating
-	 */
-	for (index = 0; index < num_gpio; ++index) {
-		temp = gpio_get_in_value(gpio[index]);
-		value[index] = ((value[index] ^ temp) << 1) | temp;
-	}
-
-	/* Disable pull up / pull down to conserve power */
-	for (index = 0; index < num_gpio; ++index)
-		gpio_input(gpio[index]);
-
-	return 0;
-}
-
 int gpio_get_int_status(gpio_t gpio)
 {
 	int bit = gpio % GPIO_GPIOS_PER_PORT;
@@ -279,3 +228,18 @@ void gpio_set_int_clear(gpio_t gpio)
 			offsetof(struct gpio_bank, int_clear),
 			1 << bit, 1 << bit);
 }
+
+void gpio_input_pulldown(gpio_t gpio)
+{
+	__gpio_input(gpio, PINMUX_PULL_DOWN);
+}
+
+void gpio_input_pullup(gpio_t gpio)
+{
+	__gpio_input(gpio, PINMUX_PULL_UP);
+}
+
+void gpio_input(gpio_t gpio)
+{
+	__gpio_input(gpio, PINMUX_PULL_NONE);
+}
diff --git a/src/soc/nvidia/tegra/gpio.h b/src/soc/nvidia/tegra/gpio.h
index 5f6833af79..43f898958e 100644
--- a/src/soc/nvidia/tegra/gpio.h
+++ b/src/soc/nvidia/tegra/gpio.h
@@ -21,12 +21,10 @@
 #define __SOC_NVIDIA_TEGRA_GPIO_H__
 
 #include <stdint.h>
+#include <gpiolib.h>
 
 #include "pinmux.h"
 
-/* Wrapper type for GPIOs. Always use GPIO() macro to generate. */
-typedef u32 gpio_t;
-
 #define GPIO_PINMUX_SHIFT 16
 #define GPIO(name) ((gpio_t)(GPIO_##name##_INDEX | \
 			     (PINMUX_GPIO_##name << GPIO_PINMUX_SHIFT)))
@@ -46,21 +44,6 @@ static inline void gpio_output_open_drain(gpio_t gpio, int value)
 	__gpio_output(gpio, value, PINMUX_OPEN_DRAIN);
 }
 
-static inline void gpio_input(gpio_t gpio)
-{
-	__gpio_input(gpio, PINMUX_PULL_NONE);
-}
-
-static inline void gpio_input_pulldown(gpio_t gpio)
-{
-	__gpio_input(gpio, PINMUX_PULL_DOWN);
-}
-
-static inline void gpio_input_pullup(gpio_t gpio)
-{
-	__gpio_input(gpio, PINMUX_PULL_UP);
-}
-
 /* Functions to modify specific GPIO control values. */
 
 enum gpio_mode {
@@ -77,12 +60,8 @@ int gpio_get_lock(gpio_t gpio);
 void gpio_set_out_enable(gpio_t gpio, int enable);
 int gpio_get_out_enable(gpio_t gpio);
 
-void gpio_set_out_value(gpio_t gpio, int value);
 int gpio_get_out_value(gpio_t gpio);
 
-int gpio_get_in_value(gpio_t gpio);
-int gpio_get_in_tristate_values(gpio_t gpio[], int num_gpio, int value[]);
-
 int gpio_get_int_status(gpio_t gpio);
 
 void gpio_set_int_enable(gpio_t gpio, int enable);
diff --git a/src/soc/qualcomm/ipq806x/include/gpio.h b/src/soc/qualcomm/ipq806x/include/gpio.h
index c1cefd4a8b..1f35aa7061 100644
--- a/src/soc/qualcomm/ipq806x/include/gpio.h
+++ b/src/soc/qualcomm/ipq806x/include/gpio.h
@@ -33,7 +33,7 @@
 #ifndef __SOC_QUALCOMM_IPQ806X_GPIO_H_
 #define __SOC_QUALCOMM_IPQ806X_GPIO_H_
 
-typedef unsigned int gpio_t;
+#include <gpiolib.h>
 
 #define GPIO_FUNC_ENABLE			1
 #define GPIO_FUNC_DISABLE			0