diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index 84b0a2d..37da641 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -60,4 +60,12 @@ config ALTERA_MBOX
 	  An implementation of the Altera Mailbox soft core. It is used
 	  to send message between processors. Say Y here if you want to use the
 	  Altera mailbox support.
+
+config TEGRA_XUSB_MBOX
+	tristate "NVIDIA Tegra XUSB Mailbox"
+	depends on MFD_TEGRA_XUSB
+	help
+	  Mailbox driver for the XUSB complex found on NVIDIA Tegra124 and
+	  later SoCs.  The XUSB mailbox is used to communicate between the
+	  XUSB microcontroller and the host processor.
 endif
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index b18201e..d77012a 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -11,3 +11,5 @@ obj-$(CONFIG_OMAP2PLUS_MBOX)	+= omap-mailbox.o
 obj-$(CONFIG_PCC)		+= pcc.o
 
 obj-$(CONFIG_ALTERA_MBOX)	+= mailbox-altera.o
+
+obj-$(CONFIG_TEGRA_XUSB_MBOX)	+= tegra-xusb-mailbox.o
diff --git a/drivers/mailbox/tegra-xusb-mailbox.c b/drivers/mailbox/tegra-xusb-mailbox.c
new file mode 100644
index 0000000..4e2477d
--- /dev/null
+++ b/drivers/mailbox/tegra-xusb-mailbox.c
@@ -0,0 +1,290 @@
+/*
+ * NVIDIA Tegra XUSB mailbox driver
+ *
+ * Copyright (C) 2014 NVIDIA Corporation
+ * Copyright (C) 2014 Google, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mailbox_controller.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#include <soc/tegra/xusb.h>
+
+#define XUSB_MBOX_NUM_CHANS			2 /* Host + PHY */
+
+#define XUSB_CFG_ARU_MBOX_CMD			0xe4
+#define  MBOX_DEST_FALC				BIT(27)
+#define  MBOX_DEST_PME				BIT(28)
+#define  MBOX_DEST_SMI				BIT(29)
+#define  MBOX_DEST_XHCI				BIT(30)
+#define  MBOX_INT_EN				BIT(31)
+#define XUSB_CFG_ARU_MBOX_DATA_IN		0xe8
+#define  CMD_DATA_SHIFT				0
+#define  CMD_DATA_MASK				0xffffff
+#define  CMD_TYPE_SHIFT				24
+#define  CMD_TYPE_MASK				0xff
+#define XUSB_CFG_ARU_MBOX_DATA_OUT		0xec
+#define XUSB_CFG_ARU_MBOX_OWNER			0xf0
+#define  MBOX_OWNER_NONE			0
+#define  MBOX_OWNER_FW				1
+#define  MBOX_OWNER_SW				2
+#define XUSB_CFG_ARU_SMI_INTR			0x428
+#define  MBOX_SMI_INTR_FW_HANG			BIT(1)
+#define  MBOX_SMI_INTR_EN			BIT(3)
+
+struct tegra_xusb_mbox {
+	struct mbox_controller mbox;
+	struct regmap *fpci_regs;
+	spinlock_t lock;
+	int irq;
+};
+
+static inline u32 mbox_readl(struct tegra_xusb_mbox *mbox, unsigned long offset)
+{
+	u32 val;
+
+	regmap_read(mbox->fpci_regs, offset, &val);
+
+	return val;
+}
+
+static inline void mbox_writel(struct tegra_xusb_mbox *mbox, u32 val,
+			       unsigned long offset)
+{
+	regmap_write(mbox->fpci_regs, offset, val);
+}
+
+static inline struct tegra_xusb_mbox *to_tegra_mbox(struct mbox_controller *c)
+{
+	return container_of(c, struct tegra_xusb_mbox, mbox);
+}
+
+static inline u32 mbox_pack_msg(struct tegra_xusb_mbox_msg *msg)
+{
+	u32 val;
+
+	val = (msg->cmd & CMD_TYPE_MASK) << CMD_TYPE_SHIFT;
+	val |= (msg->data & CMD_DATA_MASK) << CMD_DATA_SHIFT;
+
+	return val;
+}
+
+static inline void mbox_unpack_msg(u32 val, struct tegra_xusb_mbox_msg *msg)
+{
+	msg->cmd = (val >> CMD_TYPE_SHIFT) & CMD_TYPE_MASK;
+	msg->data = (val >> CMD_DATA_SHIFT) & CMD_DATA_MASK;
+}
+
+static bool mbox_cmd_requires_ack(enum tegra_xusb_mbox_cmd cmd)
+{
+	switch (cmd) {
+	case MBOX_CMD_SET_BW:
+	case MBOX_CMD_ACK:
+	case MBOX_CMD_NAK:
+		return false;
+	default:
+		return true;
+	}
+}
+
+static int tegra_xusb_mbox_send_data(struct mbox_chan *chan, void *data)
+{
+	struct tegra_xusb_mbox *mbox = to_tegra_mbox(chan->mbox);
+	struct tegra_xusb_mbox_msg *msg = data;
+	unsigned long flags;
+	u32 reg;
+
+	dev_dbg(mbox->mbox.dev, "TX message %#x:%#x\n", msg->cmd, msg->data);
+
+	spin_lock_irqsave(&mbox->lock, flags);
+	/*
+	 * Acquire the mailbox.  The firmware still owns the mailbox for
+	 * ACK/NAK messages.
+	 */
+	if (!(msg->cmd == MBOX_CMD_ACK || msg->cmd == MBOX_CMD_NAK)) {
+		if (mbox_readl(mbox, XUSB_CFG_ARU_MBOX_OWNER) !=
+		    MBOX_OWNER_NONE) {
+			dev_err(mbox->mbox.dev, "Mailbox not idle\n");
+			goto busy;
+		}
+
+		mbox_writel(mbox, MBOX_OWNER_SW, XUSB_CFG_ARU_MBOX_OWNER);
+		if (mbox_readl(mbox, XUSB_CFG_ARU_MBOX_OWNER) !=
+		    MBOX_OWNER_SW) {
+			dev_err(mbox->mbox.dev, "Failed to acquire mailbox");
+			goto busy;
+		}
+	}
+
+	mbox_writel(mbox, mbox_pack_msg(msg), XUSB_CFG_ARU_MBOX_DATA_IN);
+	reg = mbox_readl(mbox, XUSB_CFG_ARU_MBOX_CMD);
+	reg |= MBOX_INT_EN | MBOX_DEST_FALC;
+	mbox_writel(mbox, reg, XUSB_CFG_ARU_MBOX_CMD);
+
+	spin_unlock_irqrestore(&mbox->lock, flags);
+
+	return 0;
+busy:
+	spin_unlock_irqrestore(&mbox->lock, flags);
+	return -EBUSY;
+}
+
+static int tegra_xusb_mbox_startup(struct mbox_chan *chan)
+{
+	return 0;
+}
+
+static void tegra_xusb_mbox_shutdown(struct mbox_chan *chan)
+{
+}
+
+static bool tegra_xusb_mbox_last_tx_done(struct mbox_chan *chan)
+{
+	struct tegra_xusb_mbox *mbox = to_tegra_mbox(chan->mbox);
+
+	return mbox_readl(mbox, XUSB_CFG_ARU_MBOX_OWNER) == MBOX_OWNER_NONE;
+}
+
+static const struct mbox_chan_ops tegra_xusb_mbox_chan_ops = {
+	.send_data = tegra_xusb_mbox_send_data,
+	.startup = tegra_xusb_mbox_startup,
+	.shutdown = tegra_xusb_mbox_shutdown,
+	.last_tx_done = tegra_xusb_mbox_last_tx_done,
+};
+
+static irqreturn_t tegra_xusb_mbox_irq(int irq, void *p)
+{
+	struct tegra_xusb_mbox *mbox = p;
+	struct tegra_xusb_mbox_msg msg;
+	unsigned int i;
+	u32 reg;
+
+	spin_lock(&mbox->lock);
+
+	/* Clear mbox interrupts */
+	reg = mbox_readl(mbox, XUSB_CFG_ARU_SMI_INTR);
+	if (reg & MBOX_SMI_INTR_FW_HANG)
+		dev_err(mbox->mbox.dev, "Controller firmware hang\n");
+	mbox_writel(mbox, reg, XUSB_CFG_ARU_SMI_INTR);
+
+	reg = mbox_readl(mbox, XUSB_CFG_ARU_MBOX_DATA_OUT);
+	mbox_unpack_msg(reg, &msg);
+
+	reg = mbox_readl(mbox, XUSB_CFG_ARU_MBOX_CMD);
+	reg &= ~MBOX_DEST_SMI;
+	mbox_writel(mbox, reg, XUSB_CFG_ARU_MBOX_CMD);
+
+	/* Clear mailbox owner if no ACK/NAK is required. */
+	if (!mbox_cmd_requires_ack(msg.cmd))
+		mbox_writel(mbox, MBOX_OWNER_NONE, XUSB_CFG_ARU_MBOX_OWNER);
+
+	dev_dbg(mbox->mbox.dev, "RX message %#x:%#x\n", msg.cmd, msg.data);
+	for (i = 0; i < XUSB_MBOX_NUM_CHANS; i++) {
+		if (mbox->mbox.chans[i].cl)
+			mbox_chan_received_data(&mbox->mbox.chans[i], &msg);
+	}
+
+	spin_unlock(&mbox->lock);
+
+	return IRQ_HANDLED;
+}
+
+static struct mbox_chan *tegra_xusb_mbox_of_xlate(struct mbox_controller *ctlr,
+					const struct of_phandle_args *sp)
+{
+	struct tegra_xusb_mbox *mbox = to_tegra_mbox(ctlr);
+	struct mbox_chan *chan = ERR_PTR(-EINVAL);
+	unsigned long flags;
+	unsigned int i;
+
+	/* Pick the first available (virtual) channel. */
+	spin_lock_irqsave(&mbox->lock, flags);
+	for (i = 0; XUSB_MBOX_NUM_CHANS; i++) {
+		if (!ctlr->chans[i].cl) {
+			chan = &ctlr->chans[i];
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&mbox->lock, flags);
+
+	return chan;
+}
+
+static const struct of_device_id tegra_xusb_mbox_of_match[] = {
+	{ .compatible = "nvidia,tegra124-xusb-mbox" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, tegra_xusb_mbox_of_match);
+
+static int tegra_xusb_mbox_probe(struct platform_device *pdev)
+{
+	struct tegra_xusb_mbox *mbox;
+	int ret;
+
+	mbox = devm_kzalloc(&pdev->dev, sizeof(*mbox), GFP_KERNEL);
+	if (!mbox)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, mbox);
+	spin_lock_init(&mbox->lock);
+	mbox->fpci_regs = dev_get_drvdata(pdev->dev.parent);
+
+	mbox->mbox.dev = &pdev->dev;
+	mbox->mbox.chans = devm_kcalloc(&pdev->dev, XUSB_MBOX_NUM_CHANS,
+					sizeof(*mbox->mbox.chans), GFP_KERNEL);
+	if (!mbox->mbox.chans)
+		return -ENOMEM;
+	mbox->mbox.num_chans = XUSB_MBOX_NUM_CHANS;
+	mbox->mbox.ops = &tegra_xusb_mbox_chan_ops;
+	mbox->mbox.txdone_poll = true;
+	mbox->mbox.txpoll_period = 1;
+	mbox->mbox.of_xlate = tegra_xusb_mbox_of_xlate;
+
+	mbox->irq = platform_get_irq(pdev, 0);
+	if (mbox->irq < 0)
+		return mbox->irq;
+	ret = devm_request_irq(&pdev->dev, mbox->irq, tegra_xusb_mbox_irq, 0,
+			       dev_name(&pdev->dev), mbox);
+	if (ret < 0)
+		return ret;
+
+	ret = mbox_controller_register(&mbox->mbox);
+	if (ret < 0)
+		dev_err(&pdev->dev, "failed to register mailbox: %d\n", ret);
+
+	return ret;
+}
+
+static int tegra_xusb_mbox_remove(struct platform_device *pdev)
+{
+	struct tegra_xusb_mbox *mbox = platform_get_drvdata(pdev);
+
+	synchronize_irq(mbox->irq);
+	devm_free_irq(&pdev->dev, mbox->irq, mbox);
+	mbox_controller_unregister(&mbox->mbox);
+
+	return 0;
+}
+
+static struct platform_driver tegra_xusb_mbox_driver = {
+	.probe = tegra_xusb_mbox_probe,
+	.remove = tegra_xusb_mbox_remove,
+	.driver = {
+		.name = "tegra-xusb-mbox",
+		.of_match_table = tegra_xusb_mbox_of_match,
+	},
+};
+module_platform_driver(tegra_xusb_mbox_driver);
+
+MODULE_AUTHOR("Andrew Bresticker <abrestic@chromium.org>");
+MODULE_DESCRIPTION("NVIDIA Tegra XUSB mailbox driver");
+MODULE_LICENSE("GPL v2");
diff --git a/include/soc/tegra/xusb.h b/include/soc/tegra/xusb.h
new file mode 100644
index 0000000..5ce5e12
--- /dev/null
+++ b/include/soc/tegra/xusb.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2014 NVIDIA Corporation
+ * Copyright (C) 2014 Google, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ */
+
+#ifndef __SOC_TEGRA_XUSB_H__
+#define __SOC_TEGRA_XUSB_H__
+
+/* Command requests from the firmware */
+enum tegra_xusb_mbox_cmd {
+	MBOX_CMD_MSG_ENABLED = 1,
+	MBOX_CMD_INC_FALC_CLOCK,
+	MBOX_CMD_DEC_FALC_CLOCK,
+	MBOX_CMD_INC_SSPI_CLOCK,
+	MBOX_CMD_DEC_SSPI_CLOCK,
+	MBOX_CMD_SET_BW, /* no ACK/NAK required */
+	MBOX_CMD_SET_SS_PWR_GATING,
+	MBOX_CMD_SET_SS_PWR_UNGATING,
+	MBOX_CMD_SAVE_DFE_CTLE_CTX,
+	MBOX_CMD_AIRPLANE_MODE_ENABLED, /* unused */
+	MBOX_CMD_AIRPLANE_MODE_DISABLED, /* unused */
+	MBOX_CMD_START_HSIC_IDLE,
+	MBOX_CMD_STOP_HSIC_IDLE,
+	MBOX_CMD_DBC_WAKE_STACK, /* unused */
+	MBOX_CMD_HSIC_PRETEND_CONNECT,
+
+	MBOX_CMD_MAX,
+
+	/* Response message to above commands */
+	MBOX_CMD_ACK = 128,
+	MBOX_CMD_NAK
+};
+
+struct tegra_xusb_mbox_msg {
+	u32 cmd;
+	u32 data;
+};
+
+#endif /* __SOC_TEGRA_XUSB_H__ */
