diff --git a/Documentation/devicetree/bindings/i2c/i2c-cros-ec-tunnel.txt b/Documentation/devicetree/bindings/i2c/i2c-cros-ec-tunnel.txt
new file mode 100644
index 0000000000000..898f030eba622
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-cros-ec-tunnel.txt
@@ -0,0 +1,39 @@
+I2C bus that tunnels through the ChromeOS EC (cros-ec)
+======================================================
+On some ChromeOS board designs we've got a connection to the EC (embedded
+controller) but no direct connection to some devices on the other side of
+the EC (like a battery and PMIC). To get access to those devices we need
+to tunnel our i2c commands through the EC.
+
+The node for this device should be under a cros-ec node like google,cros-ec-spi
+or google,cros-ec-i2c.
+
+
+Required properties:
+- compatible: google,cros-ec-i2c-tunnel
+- google,remote-bus: The EC bus we'd like to talk to.
+
+Optional child nodes:
+- One node per I2C device connected to the tunnelled I2C bus.
+
+
+Example:
+ cros-ec@0 {
+ compatible = "google,cros-ec-spi";
+
+ ...
+
+ i2c-tunnel {
+ compatible = "google,cros-ec-i2c-tunnel";
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ google,remote-bus = <0>;
+
+ battery: sbs-battery@b {
+ compatible = "sbs,sbs-battery";
+ reg = <0xb>;
+ sbs,poll-retry-count = <1>;
+ };
+ };
+ }
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index c94db1c5e3538..9a0a6cc7f4ba8 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -993,6 +993,15 @@ config I2C_SIBYTE
help
Supports the SiByte SOC on-chip I2C interfaces (2 channels).
+config I2C_CROS_EC_TUNNEL
+ tristate "ChromeOS EC tunnel I2C bus"
+ depends on MFD_CROS_EC
+ help
+ If you say yes here you get an I2C bus that will tunnel i2c commands
+ through to the other side of the ChromeOS EC to the i2c bus
+ connected there. This will work whatever the interface used to
+ talk to the EC (SPI, I2C or LPC).
+
config SCx200_I2C
tristate "NatSemi SCx200 I2C using GPIO pins (DEPRECATED)"
depends on SCx200_GPIO
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 18d18ff9db939..e110ca932918f 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -95,6 +95,7 @@ obj-$(CONFIG_I2C_VIPERBOARD) += i2c-viperboard.o
# Other I2C/SMBus bus drivers
obj-$(CONFIG_I2C_ACORN) += i2c-acorn.o
obj-$(CONFIG_I2C_BCM_KONA) += i2c-bcm-kona.o
+obj-$(CONFIG_I2C_CROS_EC_TUNNEL) += i2c-cros-ec-tunnel.o
obj-$(CONFIG_I2C_ELEKTOR) += i2c-elektor.o
obj-$(CONFIG_I2C_PCA_ISA) += i2c-pca-isa.o
obj-$(CONFIG_I2C_SIBYTE) += i2c-sibyte.o
diff --git a/drivers/i2c/busses/i2c-cros-ec-tunnel.c b/drivers/i2c/busses/i2c-cros-ec-tunnel.c
new file mode 100644
index 0000000000000..8e7a71487bb16
--- /dev/null
+++ b/drivers/i2c/busses/i2c-cros-ec-tunnel.c
@@ -0,0 +1,318 @@
+/*
+ * Copyright (C) 2013 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; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Expose an I2C passthrough to the ChromeOS EC.
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/mfd/cros_ec.h>
+#include <linux/mfd/cros_ec_commands.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+/**
+ * struct ec_i2c_device - Driver data for I2C tunnel
+ *
+ * @dev: Device node
+ * @adap: I2C adapter
+ * @ec: Pointer to EC device
+ * @remote_bus: The EC bus number we tunnel to on the other side.
+ * @request_buf: Buffer for transmitting data; we expect most transfers to fit.
+ * @response_buf: Buffer for receiving data; we expect most transfers to fit.
+ */
+
+struct ec_i2c_device {
+ struct device *dev;
+ struct i2c_adapter adap;
+ struct cros_ec_device *ec;
+
+ u16 remote_bus;
+
+ u8 request_buf[256];
+ u8 response_buf[256];
+};
+
+/**
+ * ec_i2c_count_message - Count bytes needed for ec_i2c_construct_message
+ *
+ * @i2c_msgs: The i2c messages to read
+ * @num: The number of i2c messages.
+ *
+ * Returns the number of bytes the messages will take up.
+ */
+static int ec_i2c_count_message(const struct i2c_msg i2c_msgs[], int num)
+{
+ int i;
+ int size;
+
+ size = sizeof(struct ec_params_i2c_passthru);
+ size += num * sizeof(struct ec_params_i2c_passthru_msg);
+ for (i = 0; i < num; i++)
+ if (!(i2c_msgs[i].flags & I2C_M_RD))
+ size += i2c_msgs[i].len;
+
+ return size;
+}
+
+/**
+ * ec_i2c_construct_message - construct a message to go to the EC
+ *
+ * This function effectively stuffs the standard i2c_msg format of Linux into
+ * a format that the EC understands.
+ *
+ * @buf: The buffer to fill. We assume that the buffer is big enough.
+ * @i2c_msgs: The i2c messages to read.
+ * @num: The number of i2c messages.
+ * @bus_num: The remote bus number we want to talk to.
+ *
+ * Returns 0 or a negative error number.
+ */
+static int ec_i2c_construct_message(u8 *buf, const struct i2c_msg i2c_msgs[],
+ int num, u16 bus_num)
+{
+ struct ec_params_i2c_passthru *params;
+ u8 *out_data;
+ int i;
+
+ out_data = buf + sizeof(struct ec_params_i2c_passthru) +
+ num * sizeof(struct ec_params_i2c_passthru_msg);
+
+ params = (struct ec_params_i2c_passthru *)buf;
+ params->port = bus_num;
+ params->num_msgs = num;
+ for (i = 0; i < num; i++) {
+ const struct i2c_msg *i2c_msg = &i2c_msgs[i];
+ struct ec_params_i2c_passthru_msg *msg = ¶ms->msg[i];
+
+ msg->len = i2c_msg->len;
+ msg->addr_flags = i2c_msg->addr;
+
+ if (i2c_msg->flags & I2C_M_TEN)
+ msg->addr_flags |= EC_I2C_FLAG_10BIT;
+
+ if (i2c_msg->flags & I2C_M_RD) {
+ msg->addr_flags |= EC_I2C_FLAG_READ;
+ } else {
+ memcpy(out_data, i2c_msg->buf, msg->len);
+ out_data += msg->len;
+ }
+ }
+
+ return 0;
+}
+
+/**
+ * ec_i2c_count_response - Count bytes needed for ec_i2c_parse_response
+ *
+ * @i2c_msgs: The i2c messages to to fill up.
+ * @num: The number of i2c messages expected.
+ *
+ * Returns the number of response bytes expeced.
+ */
+static int ec_i2c_count_response(struct i2c_msg i2c_msgs[], int num)
+{
+ int size;
+ int i;
+
+ size = sizeof(struct ec_response_i2c_passthru);
+ for (i = 0; i < num; i++)
+ if (i2c_msgs[i].flags & I2C_M_RD)
+ size += i2c_msgs[i].len;
+
+ return size;
+}
+
+/**
+ * ec_i2c_parse_response - Parse a response from the EC
+ *
+ * We'll take the EC's response and copy it back into msgs.
+ *
+ * @buf: The buffer to parse.
+ * @i2c_msgs: The i2c messages to to fill up.
+ * @num: The number of i2c messages; will be modified to include the actual
+ * number received.
+ *
+ * Returns 0 or a negative error number.
+ */
+static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[],
+ int *num)
+{
+ const struct ec_response_i2c_passthru *resp;
+ const u8 *in_data;
+ int i;
+
+ in_data = buf + sizeof(struct ec_response_i2c_passthru);
+
+ resp = (const struct ec_response_i2c_passthru *)buf;
+ if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT)
+ return -ETIMEDOUT;
+ else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
+ return -EREMOTEIO;
+
+ /* Other side could send us back fewer messages, but not more */
+ if (resp->num_msgs > *num)
+ return -EPROTO;
+ *num = resp->num_msgs;
+
+ for (i = 0; i < *num; i++) {
+ struct i2c_msg *i2c_msg = &i2c_msgs[i];
+
+ if (i2c_msgs[i].flags & I2C_M_RD) {
+ memcpy(i2c_msg->buf, in_data, i2c_msg->len);
+ in_data += i2c_msg->len;
+ }
+ }
+
+ return 0;
+}
+
+static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
+ int num)
+{
+ struct ec_i2c_device *bus = adap->algo_data;
+ struct device *dev = bus->dev;
+ const u16 bus_num = bus->remote_bus;
+ int request_len;
+ int response_len;
+ u8 *request = NULL;
+ u8 *response = NULL;
+ int result;
+
+ request_len = ec_i2c_count_message(i2c_msgs, num);
+ if (request_len < 0) {
+ dev_warn(dev, "Error constructing message %d\n", request_len);
+ result = request_len;
+ goto exit;
+ }
+ response_len = ec_i2c_count_response(i2c_msgs, num);
+ if (response_len < 0) {
+ /* Unexpected; no errors should come when NULL response */
+ dev_warn(dev, "Error preparing response %d\n", response_len);
+ result = response_len;
+ goto exit;
+ }
+
+ if (request_len <= ARRAY_SIZE(bus->request_buf)) {
+ request = bus->request_buf;
+ } else {
+ request = kzalloc(request_len, GFP_KERNEL);
+ if (request == NULL) {
+ result = -ENOMEM;
+ goto exit;
+ }
+ }
+ if (response_len <= ARRAY_SIZE(bus->response_buf)) {
+ response = bus->response_buf;
+ } else {
+ response = kzalloc(response_len, GFP_KERNEL);
+ if (response == NULL) {
+ result = -ENOMEM;
+ goto exit;
+ }
+ }
+
+ ec_i2c_construct_message(request, i2c_msgs, num, bus_num);
+ result = bus->ec->command_sendrecv(bus->ec, EC_CMD_I2C_PASSTHRU,
+ request, request_len,
+ response, response_len);
+ if (result)
+ goto exit;
+
+ result = ec_i2c_parse_response(response, i2c_msgs, &num);
+ if (result < 0)
+ goto exit;
+
+ /* Indicate success by saying how many messages were sent */
+ result = num;
+exit:
+ if (request != bus->request_buf)
+ kfree(request);
+ if (response != bus->response_buf)
+ kfree(response);
+
+ return result;
+}
+
+static u32 ec_i2c_functionality(struct i2c_adapter *adap)
+{
+ return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm ec_i2c_algorithm = {
+ .master_xfer = ec_i2c_xfer,
+ .functionality = ec_i2c_functionality,
+};
+
+static int ec_i2c_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
+ struct device *dev = &pdev->dev;
+ struct ec_i2c_device *bus = NULL;
+ u32 remote_bus;
+ int err;
+
+ if (!ec->command_sendrecv) {
+ dev_err(dev, "Missing sendrecv\n");
+ return -EINVAL;
+ }
+
+ bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
+ if (bus == NULL)
+ return -ENOMEM;
+
+ err = of_property_read_u32(np, "google,remote-bus", &remote_bus);
+ if (err) {
+ dev_err(dev, "Couldn't read remote-bus property\n");
+ return err;
+ }
+ bus->remote_bus = remote_bus;
+
+ bus->ec = ec;
+ bus->dev = dev;
+
+ bus->adap.owner = THIS_MODULE;
+ strlcpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name));
+ bus->adap.algo = &ec_i2c_algorithm;
+ bus->adap.algo_data = bus;
+ bus->adap.dev.parent = &pdev->dev;
+ bus->adap.dev.of_node = np;
+
+ err = i2c_add_adapter(&bus->adap);
+ if (err) {
+ dev_err(dev, "cannot register i2c adapter\n");
+ return err;
+ }
+ platform_set_drvdata(pdev, bus);
+
+ return err;
+}
+
+static int ec_i2c_remove(struct platform_device *dev)
+{
+ struct ec_i2c_device *bus = platform_get_drvdata(dev);
+
+ i2c_del_adapter(&bus->adap);
+
+ return 0;
+}
+
+static struct platform_driver ec_i2c_tunnel_driver = {
+ .probe = ec_i2c_probe,
+ .remove = ec_i2c_remove,
+ .driver = {
+ .name = "cros-ec-i2c-tunnel",
+ },
+};
+
+module_platform_driver(ec_i2c_tunnel_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("EC I2C tunnel driver");
+MODULE_ALIAS("platform:cros-ec-i2c-tunnel");
diff --git a/drivers/mfd/cros_ec.c b/drivers/mfd/cros_ec.c
index 8b6fb34c9b31b..38fe9bf0d169b 100644
--- a/drivers/mfd/cros_ec.c
+++ b/drivers/mfd/cros_ec.c
@@ -90,6 +90,11 @@ static const struct mfd_cell cros_devs[] = {
.id = 1,
.of_compatible = "google,cros-ec-keyb",
},
+ {
+ .name = "cros-ec-i2c-tunnel",
+ .id = 2,
+ .of_compatible = "google,cros-ec-i2c-tunnel",
+ },
};
int cros_ec_register(struct cros_ec_device *ec_dev)