11 files changed, 497 insertions, 5 deletions

diff --git a/src/cpu/allwinner/a10/twi.c b/src/cpu/allwinner/a10/twi.c
index 14e5ec7d9f..d6a0127803 100644
--- a/src/cpu/allwinner/a10/twi.c
+++ b/src/cpu/allwinner/a10/twi.c
@@ -215,7 +215,7 @@ static int i2c_write(unsigned bus, unsigned chip, unsigned addr,
  * TODO: Rewite the i2c_transfer and supporting functions
  *
  */
-int i2c_transfer(unsigned bus, struct i2c_seg *segments, int count)
+int platform_i2c_transfer(unsigned bus, struct i2c_seg *segments, int count)
 {
 	struct i2c_seg *seg = segments;
 
diff --git a/src/device/Kconfig b/src/device/Kconfig
index bd2f34b618..67d01e077a 100644
--- a/src/device/Kconfig
+++ b/src/device/Kconfig
@@ -376,6 +376,16 @@ config PXE_ROM_ID
 
 	  Under GNU/Linux you can run `lspci -nn` to list the IDs of your PCI devices.
 
+config SOFTWARE_I2C
+	bool "Enable I2C controller emulation in software"
+	default n
+	help
+	  This config option will enable code to override the i2c_transfer
+	  routine with a (simple) software emulation of the protocol. This may
+	  be useful for debugging or on platforms where a driver for the real
+	  I2C controller is not (yet) available. The platform code needs to
+	  provide bindings to manually toggle I2C lines.
+	  
 endmenu
 
 menu "Display"
diff --git a/src/device/Makefile.inc b/src/device/Makefile.inc
index a7f336489d..7fdd9b587d 100644
--- a/src/device/Makefile.inc
+++ b/src/device/Makefile.inc
@@ -24,3 +24,7 @@ romstage-$(CONFIG_PCI) += pci_early.c
 subdirs-y += oprom dram
 
 ramstage-$(CONFIG_VGA_ROM_RUN) += pci_rom.c
+
+bootblock-$(CONFIG_SOFTWARE_I2C) += software_i2c.c
+romstage-$(CONFIG_SOFTWARE_I2C) += software_i2c.c
+ramstage-$(CONFIG_SOFTWARE_I2C) += software_i2c.c
diff --git a/src/device/software_i2c.c b/src/device/software_i2c.c
new file mode 100644
index 0000000000..6c9c200dc7
--- /dev/null
+++ b/src/device/software_i2c.c
@@ -0,0 +1,345 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 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 <assert.h>
+#include <timer.h>
+#include <console/console.h>
+#include <device/i2c.h>
+
+/*
+ * The implementation is based on Wikipedia.
+ */
+
+#define DEBUG 0		/* Set to 1 for per-byte output */
+#define SPEW 0		/* Set to 1 for verbose bitwise/line-state output */
+#define DELAY_US 5	/* Default setup delay: 4us (+1 for timer inaccuracy) */
+#define TIMEOUT_US 50000 /* Maximum clock stretching time we want to allow */
+
+#define spew(...) do { if (SPEW) printk(BIOS_SPEW, ##__VA_ARGS__); } while (0)
+
+struct software_i2c_ops *software_i2c[SOFTWARE_I2C_MAX_BUS];
+
+/*
+ * Waits until either timeout_us have passed or (iff for_scl is set) until SCL
+ * goes high. Will report random line changes during the wait and return SCL.
+ */
+static int __wait(unsigned bus, int timeout_us, int for_scl)
+{
+	int us;
+	int sda = software_i2c[bus]->get_sda(bus);
+	int scl = software_i2c[bus]->get_scl(bus);
+	struct mono_time start;
+	timer_monotonic_get(&start);
+
+	do {
+		int old_sda = sda;
+		int old_scl = scl;
+		struct rela_time diff = current_time_from(&start);
+		us = rela_time_in_microseconds(&diff);
+
+		if (old_sda != (sda = software_i2c[bus]->get_sda(bus)))
+			spew("[SDA transitioned to %d after %dus] ", sda, us);
+		if (old_scl != (scl = software_i2c[bus]->get_scl(bus)))
+			spew("[SCL transitioned to %d after %dus] ", scl, us);
+	} while (us < timeout_us && (!for_scl || !scl));
+
+	return scl;
+}
+
+/* Waits the default DELAY_US to allow line state to stabilize. */
+static void wait(unsigned bus)
+{
+	__wait(bus, DELAY_US, 0);
+}
+
+/* Waits until SCL goes high. Prints a contextual error message on timeout. */
+static int wait_for_scl(unsigned bus, const char *error_context)
+{
+	if (!__wait(bus, TIMEOUT_US, 1)) {
+		printk(BIOS_ERR, "software_i2c(%d): ERROR: Clock stretching "
+				 "timeout %s!\n", bus, error_context);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int start_cond(unsigned bus)
+{
+	spew("software_i2c(%d): Sending start condition... ", bus);
+
+	/* SDA might not yet be high if repeated start. */
+	software_i2c[bus]->set_sda(bus, 1);
+	wait(bus);
+
+	/* Might need to wait for clock stretching if repeated start. */
+	software_i2c[bus]->set_scl(bus, 1);
+	if (wait_for_scl(bus, "before start condition"))
+		return -1;
+	wait(bus);	/* Repeated start setup time, minimum 4.7us */
+
+	if (!software_i2c[bus]->get_sda(bus)) {
+		printk(BIOS_ERR, "software_i2c(%d): Arbitration lost trying "
+			"to send start condition!\n", bus);
+		return -1;
+	}
+
+	/* SCL is high, transition SDA low as first part of start condition. */
+	software_i2c[bus]->set_sda(bus, 0);
+	wait(bus);
+	assert(software_i2c[bus]->get_scl(bus));
+
+	/* Pull SCL low to finish start condition (next pulse will be data). */
+	software_i2c[bus]->set_scl(bus, 0);
+
+	spew("Start condition transmitted!\n");
+	return 0;
+}
+
+static int stop_cond(unsigned bus)
+{
+	spew("software_i2c(%d): Sending stop condition... ", bus);
+
+	/* SDA is unknown, set it to low. SCL must be low. */
+	software_i2c[bus]->set_sda(bus, 0);
+	wait(bus);
+
+	/* Clock stretching */
+	assert(!software_i2c[bus]->get_scl(bus));
+	software_i2c[bus]->set_scl(bus, 1);
+	if (wait_for_scl(bus, "before stop condition"))
+		return -1;
+	wait(bus);	/* Stop bit setup time, minimum 4us */
+
+	/* SCL is high, transition SDA high to signal stop condition. */
+	software_i2c[bus]->set_sda(bus, 1);
+	wait(bus);
+	if (!software_i2c[bus]->get_sda(bus)) {
+		printk(BIOS_WARNING, "software_i2c(%d): WARNING: SDA low after "
+			"stop condition... access by another master or line "
+			"stuck from faulty slave?\n", bus);
+		/* Could theoretically happen with multi-master, so no -1. */
+	}
+
+	spew("Stop condition transmitted\n");
+	return 0;
+}
+
+static int out_bit(unsigned bus, int bit)
+{
+	spew("software_i2c(%d): Sending a %d bit... ", bus, bit);
+
+	software_i2c[bus]->set_sda(bus, bit);
+	wait(bus);
+
+	if (bit && !software_i2c[bus]->get_sda(bus)) {
+		printk(BIOS_ERR, "software_i2c(%d): ERROR: SDA wedged low "
+			"by slave before clock pulse on transmit!\n", bus);
+		return -1;
+	}
+
+	/* Clock stretching */
+	assert(!software_i2c[bus]->get_scl(bus));
+	software_i2c[bus]->set_scl(bus, 1);
+	if (wait_for_scl(bus, "on transmit"))
+		return -1;
+	wait(bus);
+
+	if (bit && !software_i2c[bus]->get_sda(bus)) {
+		printk(BIOS_ERR, "software_i2c(%d): ERROR: SDA wedged low "
+			"by slave after clock pulse on transmit!\n", bus);
+		return -1;
+	}
+
+	assert(software_i2c[bus]->get_scl(bus));
+	software_i2c[bus]->set_scl(bus, 0);
+
+	spew("%d bit sent!\n", bit);
+	return 0;
+}
+
+static int in_bit(unsigned bus)
+{
+	int bit;
+
+	spew("software_i2c(%d): Receiving a bit... ", bus);
+
+	/* Let the slave drive data */
+	software_i2c[bus]->set_sda(bus, 1);
+	wait(bus);
+
+	/* Clock stretching */
+	assert(!software_i2c[bus]->get_scl(bus));
+	software_i2c[bus]->set_scl(bus, 1);
+	if (wait_for_scl(bus, "on receive"))
+		return -1;
+
+	/* SCL is high, now data is valid */
+	bit = software_i2c[bus]->get_sda(bus);
+	wait(bus);
+	assert(software_i2c[bus]->get_scl(bus));
+	software_i2c[bus]->set_scl(bus, 0);
+
+	spew("Received a %d!\n", bit);
+
+	return bit;
+}
+
+/* Write a byte to I2C bus. Return 0 if ack by the slave. */
+static int out_byte(unsigned bus, u8 byte)
+{
+	unsigned bit;
+	int nack;
+
+	for (bit = 0; bit < 8; bit++)
+		if (out_bit(bus, (byte >> (7 - bit)) & 0x1) < 0)
+			return -1;
+
+	nack = in_bit(bus);
+
+	if (DEBUG && nack >= 0)
+		printk(BIOS_DEBUG, "software_i2c(%d): wrote byte 0x%02x, "
+			"received %s\n", bus, byte, nack ? "NAK" : "ACK");
+
+	return nack;
+}
+
+static int in_byte(unsigned bus, int ack)
+{
+	u8 byte = 0;
+	int i;
+	for (i = 0; i < 8; ++i) {
+		int bit = in_bit(bus);
+		if (bit < 0)
+			return -1;
+		byte = (byte << 1) | bit;
+	}
+
+	if (out_bit(bus, !ack) < 0)
+		return -1;
+
+	if (DEBUG)
+		printk(BIOS_DEBUG, "software_i2c(%d): read byte 0x%02x, "
+			"sent %s\n", bus, byte, ack ? "ACK" : "NAK");
+
+	return byte;
+}
+
+int software_i2c_transfer(unsigned bus, struct i2c_seg *segments, int count)
+{
+	int i;
+	struct i2c_seg *seg;
+
+	for (seg = segments; seg - segments < count; seg++) {
+		if (start_cond(bus) < 0)
+			return -1;
+		if (out_byte(bus, seg->chip << 1 | !!seg->read) < 0)
+			return -1;
+		for (i = 0; i < seg->len; i++) {
+			int ret;
+			if (seg->read) {
+				ret = in_byte(bus, i < seg->len - 1);
+				seg->buf[i] = (u8)ret;
+			} else {
+				ret = out_byte(bus, seg->buf[i]);
+			}
+			if (ret < 0)
+				return -1;
+		}
+	}
+	if (stop_cond(bus) < 0)
+		return -1;
+
+	return 0;
+}
+
+void software_i2c_wedge_ack(unsigned bus, u8 chip)
+{
+	int i;
+
+	/* Start a command to 'chip'... */
+	start_cond(bus);
+
+	/* Send the address bits but don't yet read the ACK. */
+	chip <<= 1;
+	for (i = 0; i < 8; ++i)
+		out_bit(bus, (chip >> (7 - i)) & 0x1);
+
+	/* Let the slave drive it's ACK but keep the clock high forever. */
+	software_i2c[bus]->set_sda(bus, 1);
+	wait(bus);
+	software_i2c[bus]->set_scl(bus, 1);
+	wait_for_scl(bus, "on wedge_ack()");
+
+	printk(BIOS_INFO, "software_i2c(%d): wedged address write on slave "
+		"ACK. SDA %d, SCL %d\n", bus, software_i2c[bus]->get_sda(bus),
+		software_i2c[bus]->get_scl(bus));
+}
+
+void software_i2c_wedge_read(unsigned bus, u8 chip, u8 reg, int bits)
+{
+	int i;
+
+	/* Start a command to 'chip'... */
+	start_cond(bus);
+	out_byte(bus, chip << 1);
+	/* ...for register 'reg'. */
+	out_byte(bus, reg);
+
+	/* Start a read command... */
+	start_cond(bus);
+	out_byte(bus, chip << 1 | 1);
+
+	/* Read bit_count bits and stop */
+	for (i = 0; i < bits; ++i)
+		in_bit(bus);
+
+	/* Let the slave drive SDA but keep the clock high forever. */
+	software_i2c[bus]->set_sda(bus, 1);
+	wait(bus);
+	software_i2c[bus]->set_scl(bus, 1);
+	wait_for_scl(bus, "on wedge_read()");
+
+	printk(BIOS_INFO, "software_i2c(%d): wedged data read after %d bits. "
+		"SDA %d, SCL %d\n", bus, bits, software_i2c[bus]->get_sda(bus),
+		software_i2c[bus]->get_scl(bus));
+}
+
+void software_i2c_wedge_write(unsigned bus, u8 chip, u8 reg, int bits)
+{
+	int i;
+
+	/* Start a command to 'chip'... */
+	start_cond(bus);
+	out_byte(bus, chip << 1);
+
+	/* Write bit_count register bits and stop */
+	for (i = 0; i < bits; ++i)
+		out_bit(bus, (reg >> (7 - i)) & 0x1);
+
+	/* Pretend to write another 1 bit but keep the clock high forever. */
+	software_i2c[bus]->set_sda(bus, 1);
+	wait(bus);
+	software_i2c[bus]->set_scl(bus, 1);
+	wait_for_scl(bus, "on wedge_write()");
+
+	printk(BIOS_INFO, "software_i2c(%d): wedged data write after %d bits. "
+		"SDA %d, SCL %d\n", bus, bits, software_i2c[bus]->get_sda(bus),
+		software_i2c[bus]->get_scl(bus));
+}
diff --git a/src/include/device/i2c.h b/src/include/device/i2c.h
index da9d1bcb3c..c1f2a2103a 100644
--- a/src/include/device/i2c.h
+++ b/src/include/device/i2c.h
@@ -31,7 +31,39 @@ struct i2c_seg
 	int len;
 };
 
-int i2c_transfer(unsigned bus, struct i2c_seg *segments, int count);
+int platform_i2c_transfer(unsigned bus, struct i2c_seg *segments, int count);
+
+#define SOFTWARE_I2C_MAX_BUS 10		/* increase as necessary */
+
+struct software_i2c_ops {
+	void (*set_sda)(unsigned bus, int high);
+	void (*set_scl)(unsigned bus, int high);
+	int (*get_sda)(unsigned bus);
+	int (*get_scl)(unsigned bus);
+};
+
+extern struct software_i2c_ops *software_i2c[];
+
+int software_i2c_transfer(unsigned bus, struct i2c_seg *segments, int count);
+void software_i2c_wedge_ack(unsigned bus, u8 chip);
+void software_i2c_wedge_read(unsigned bus, u8 chip, u8 reg, int bit_count);
+void software_i2c_wedge_write(unsigned bus, u8 chip, u8 reg, int bit_count);
+
+/*
+ * software_i2c is supposed to be a debug feature. It's usually not compiled in,
+ * but when it is it can be dynamically enabled at runtime for certain busses.
+ * Need this ugly stub to arbitrate since I2C device drivers hardcode
+ * 'i2c_transfer()' as their entry point.
+ */
+static inline int i2c_transfer(unsigned bus, struct i2c_seg *segments,
+			       int count)
+{
+	if (CONFIG_SOFTWARE_I2C)
+		if (bus < SOFTWARE_I2C_MAX_BUS && software_i2c[bus])
+			return software_i2c_transfer(bus, segments, count);
+
+	return platform_i2c_transfer(bus, segments, count);
+}
 
 /*
  * Read a raw chunk of data in one segment and one frame.
diff --git a/src/soc/nvidia/tegra/i2c.c b/src/soc/nvidia/tegra/i2c.c
index 6c269cfaed..555d0318c1 100644
--- a/src/soc/nvidia/tegra/i2c.c
+++ b/src/soc/nvidia/tegra/i2c.c
@@ -180,7 +180,7 @@ static int i2c_transfer_segment(unsigned bus, unsigned chip, int restart,
 	return 0;
 }
 
-int i2c_transfer(unsigned bus, struct i2c_seg *segments, int count)
+int platform_i2c_transfer(unsigned bus, struct i2c_seg *segments, int count)
 {
 	struct i2c_seg *seg = segments;
 
diff --git a/src/soc/nvidia/tegra/i2c.h b/src/soc/nvidia/tegra/i2c.h
index 6347fff8ad..4b1bddd2af 100644
--- a/src/soc/nvidia/tegra/i2c.h
+++ b/src/soc/nvidia/tegra/i2c.h
@@ -23,6 +23,8 @@
 #include <stdint.h>
 
 void i2c_init(unsigned bus);
+void tegra_software_i2c_init(unsigned bus);
+void tegra_software_i2c_disable(unsigned bus);
 
 enum {
 	/* Word 0 */
diff --git a/src/soc/nvidia/tegra/software_i2c.c b/src/soc/nvidia/tegra/software_i2c.c
new file mode 100644
index 0000000000..b50fb4f654
--- /dev/null
+++ b/src/soc/nvidia/tegra/software_i2c.c
@@ -0,0 +1,96 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 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 <device/i2c.h>
+#include <soc/nvidia/tegra124/gpio.h>
+#include <soc/nvidia/tegra124/pinmux.h>
+
+#include "i2c.h"
+
+static struct {
+	int pinmux_func;
+	gpio_t sda;
+	gpio_t scl;
+} pins[] = {
+	[0]{.pinmux_func = PINMUX_GEN1_I2C_SCL_FUNC_I2C1,
+	    .sda = GPIO(C5), .scl = GPIO(C4)},
+	[1]{.pinmux_func = PINMUX_GEN2_I2C_SCL_FUNC_I2C2,
+	    .sda = GPIO(T6), .scl = GPIO(T5)},
+	[2]{.pinmux_func = PINMUX_CAM_I2C_SCL_FUNC_I2C3,
+	    .sda = GPIO(BB2), .scl = GPIO(BB1)},
+	[3]{.pinmux_func = PINMUX_DDC_SCL_FUNC_I2C4,
+	    .sda = GPIO(V5), .scl = GPIO(V4)},
+	[4]{.pinmux_func = PINMUX_PWR_I2C_SCL_FUNC_I2CPMU,
+	    .sda = GPIO(Z7), .scl = GPIO(Z6)},
+};
+
+static void tegra_set_sda(unsigned bus, int high)
+{
+	if (high)
+		gpio_input_pullup(pins[bus].sda);
+	else
+		gpio_output(pins[bus].sda, 0);
+}
+
+static void tegra_set_scl(unsigned bus, int high)
+{
+	if (high)
+		gpio_input_pullup(pins[bus].scl);
+	else
+		gpio_output(pins[bus].scl, 0);
+}
+
+static int tegra_get_sda(unsigned bus)
+{
+	return gpio_get_in_value(pins[bus].sda);
+}
+
+static int tegra_get_scl(unsigned bus)
+{
+	return gpio_get_in_value(pins[bus].scl);
+}
+
+static struct software_i2c_ops tegra_ops = {
+	.set_sda = tegra_set_sda,
+	.set_scl = tegra_set_scl,
+	.get_sda = tegra_get_sda,
+	.get_scl = tegra_get_scl,
+};
+
+void tegra_software_i2c_init(unsigned bus)
+{
+	software_i2c[bus] = &tegra_ops;
+
+	/* Initialize bus to idle state. */
+	tegra_set_sda(bus, 1);
+	tegra_set_scl(bus, 1);
+}
+
+void tegra_software_i2c_disable(unsigned bus)
+{
+	software_i2c[bus] = NULL;
+
+	/* Return pins to I2C controller. */
+	pinmux_set_config(pins[bus].sda >> GPIO_PINMUX_SHIFT,
+			  pins[bus].pinmux_func | PINMUX_INPUT_ENABLE);
+	pinmux_set_config(pins[bus].scl >> GPIO_PINMUX_SHIFT,
+			  pins[bus].pinmux_func | PINMUX_INPUT_ENABLE);
+	gpio_set_mode(pins[bus].sda, GPIO_MODE_SPIO);
+	gpio_set_mode(pins[bus].scl, GPIO_MODE_SPIO);
+}
diff --git a/src/soc/nvidia/tegra124/Makefile.inc b/src/soc/nvidia/tegra124/Makefile.inc
index c7b2e16c4b..792bb9992b 100644
--- a/src/soc/nvidia/tegra124/Makefile.inc
+++ b/src/soc/nvidia/tegra124/Makefile.inc
@@ -11,6 +11,7 @@ bootblock-y += power.c
 bootblock-y += spi.c
 bootblock-y += ../tegra/gpio.c
 bootblock-y += ../tegra/i2c.c
+bootblock-$(CONFIG_SOFTWARE_I2C) += ../tegra/software_i2c.c
 bootblock-y += ../tegra/pingroup.c
 bootblock-y += ../tegra/pinmux.c
 bootblock-y += ../tegra/apbmisc.c
@@ -32,6 +33,7 @@ romstage-y += sdram_lp0.c
 romstage-y += spi.c
 romstage-y += ../tegra/gpio.c
 romstage-y += ../tegra/i2c.c
+romstage-$(CONFIG_SOFTWARE_I2C) += ../tegra/software_i2c.c
 romstage-y += ../tegra/pinmux.c
 romstage-y += timer.c
 romstage-$(CONFIG_CONSOLE_SERIAL) += uart.c
@@ -51,6 +53,7 @@ ramstage-y += spi.c
 ramstage-y += dp.c
 ramstage-y += ../tegra/gpio.c
 ramstage-y += ../tegra/i2c.c
+ramstage-$(CONFIG_SOFTWARE_I2C) += ../tegra/software_i2c.c
 ramstage-y += ../tegra/pinmux.c
 ramstage-y += ../tegra/usb.c
 ramstage-y += timer.c
diff --git a/src/soc/samsung/exynos5250/i2c.c b/src/soc/samsung/exynos5250/i2c.c
index d5d83b393a..1e526d633a 100644
--- a/src/soc/samsung/exynos5250/i2c.c
+++ b/src/soc/samsung/exynos5250/i2c.c
@@ -237,7 +237,7 @@ static int i2c_recv_buf(struct i2c_regs *regs, uint8_t *data, int len)
 	return 0;
 }
 
-int i2c_transfer(unsigned bus, struct i2c_seg *segments, int seg_count)
+int platform_i2c_transfer(unsigned bus, struct i2c_seg *segments, int seg_count)
 {
 	struct s3c24x0_i2c_bus *i2c = &i2c_busses[bus];
 	struct i2c_regs *regs = i2c->regs;
diff --git a/src/soc/samsung/exynos5420/i2c.c b/src/soc/samsung/exynos5420/i2c.c
index b79f9144a9..49875d79ed 100644
--- a/src/soc/samsung/exynos5420/i2c.c
+++ b/src/soc/samsung/exynos5420/i2c.c
@@ -633,7 +633,7 @@ static int i2c_recv_buf(struct i2c_regs *regs, uint8_t *data, int len)
 	return 0;
 }
 
-int i2c_transfer(unsigned bus, struct i2c_seg *segments, int count)
+int platform_i2c_transfer(unsigned bus, struct i2c_seg *segments, int count)
 {
 	struct i2c_bus *i2c = &i2c_busses[bus];
 	if (i2c->is_highspeed)