diff --git a/drivers/thunderbolt/Makefile b/drivers/thunderbolt/Makefile
index e276a9a62261..9828e862dd35 100644
--- a/drivers/thunderbolt/Makefile
+++ b/drivers/thunderbolt/Makefile
@@ -1,3 +1,3 @@
 obj-${CONFIG_THUNDERBOLT} := thunderbolt.o
 thunderbolt-objs := nhi.o ctl.o tb.o switch.o cap.o path.o tunnel_pci.o eeprom.o
-thunderbolt-objs += domain.o
+thunderbolt-objs += domain.o dma_port.o
diff --git a/drivers/thunderbolt/dma_port.c b/drivers/thunderbolt/dma_port.c
new file mode 100644
index 000000000000..af6dde347bee
--- /dev/null
+++ b/drivers/thunderbolt/dma_port.c
@@ -0,0 +1,524 @@
+/*
+ * Thunderbolt DMA configuration based mailbox support
+ *
+ * Copyright (C) 2017, Intel Corporation
+ * Authors: Michael Jamet <michael.jamet@intel.com>
+ *          Mika Westerberg <mika.westerberg@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/delay.h>
+#include <linux/slab.h>
+
+#include "dma_port.h"
+#include "tb_regs.h"
+
+#define DMA_PORT_CAP			0x3e
+
+#define MAIL_DATA			1
+#define MAIL_DATA_DWORDS		16
+
+#define MAIL_IN				17
+#define MAIL_IN_CMD_SHIFT		28
+#define MAIL_IN_CMD_MASK		GENMASK(31, 28)
+#define MAIL_IN_CMD_FLASH_WRITE		0x0
+#define MAIL_IN_CMD_FLASH_UPDATE_AUTH	0x1
+#define MAIL_IN_CMD_FLASH_READ		0x2
+#define MAIL_IN_CMD_POWER_CYCLE		0x4
+#define MAIL_IN_DWORDS_SHIFT		24
+#define MAIL_IN_DWORDS_MASK		GENMASK(27, 24)
+#define MAIL_IN_ADDRESS_SHIFT		2
+#define MAIL_IN_ADDRESS_MASK		GENMASK(23, 2)
+#define MAIL_IN_CSS			BIT(1)
+#define MAIL_IN_OP_REQUEST		BIT(0)
+
+#define MAIL_OUT			18
+#define MAIL_OUT_STATUS_RESPONSE	BIT(29)
+#define MAIL_OUT_STATUS_CMD_SHIFT	4
+#define MAIL_OUT_STATUS_CMD_MASK	GENMASK(7, 4)
+#define MAIL_OUT_STATUS_MASK		GENMASK(3, 0)
+#define MAIL_OUT_STATUS_COMPLETED	0
+#define MAIL_OUT_STATUS_ERR_AUTH	1
+#define MAIL_OUT_STATUS_ERR_ACCESS	2
+
+#define DMA_PORT_TIMEOUT		5000 /* ms */
+#define DMA_PORT_RETRIES		3
+
+/**
+ * struct tb_dma_port - DMA control port
+ * @sw: Switch the DMA port belongs to
+ * @port: Switch port number where DMA capability is found
+ * @base: Start offset of the mailbox registers
+ * @buf: Temporary buffer to store a single block
+ */
+struct tb_dma_port {
+	struct tb_switch *sw;
+	u8 port;
+	u32 base;
+	u8 *buf;
+};
+
+/*
+ * When the switch is in safe mode it supports very little functionality
+ * so we don't validate that much here.
+ */
+static bool dma_port_match(const struct tb_cfg_request *req,
+			   const struct ctl_pkg *pkg)
+{
+	u64 route = tb_cfg_get_route(pkg->buffer) & ~BIT_ULL(63);
+
+	if (pkg->frame.eof == TB_CFG_PKG_ERROR)
+		return true;
+	if (pkg->frame.eof != req->response_type)
+		return false;
+	if (route != tb_cfg_get_route(req->request))
+		return false;
+	if (pkg->frame.size != req->response_size)
+		return false;
+
+	return true;
+}
+
+static bool dma_port_copy(struct tb_cfg_request *req, const struct ctl_pkg *pkg)
+{
+	memcpy(req->response, pkg->buffer, req->response_size);
+	return true;
+}
+
+static int dma_port_read(struct tb_ctl *ctl, void *buffer, u64 route,
+			 u32 port, u32 offset, u32 length, int timeout_msec)
+{
+	struct cfg_read_pkg request = {
+		.header = tb_cfg_make_header(route),
+		.addr = {
+			.seq = 1,
+			.port = port,
+			.space = TB_CFG_PORT,
+			.offset = offset,
+			.length = length,
+		},
+	};
+	struct tb_cfg_request *req;
+	struct cfg_write_pkg reply;
+	struct tb_cfg_result res;
+
+	req = tb_cfg_request_alloc();
+	if (!req)
+		return -ENOMEM;
+
+	req->match = dma_port_match;
+	req->copy = dma_port_copy;
+	req->request = &request;
+	req->request_size = sizeof(request);
+	req->request_type = TB_CFG_PKG_READ;
+	req->response = &reply;
+	req->response_size = 12 + 4 * length;
+	req->response_type = TB_CFG_PKG_READ;
+
+	res = tb_cfg_request_sync(ctl, req, timeout_msec);
+
+	tb_cfg_request_put(req);
+
+	if (res.err)
+		return res.err;
+
+	memcpy(buffer, &reply.data, 4 * length);
+	return 0;
+}
+
+static int dma_port_write(struct tb_ctl *ctl, const void *buffer, u64 route,
+			  u32 port, u32 offset, u32 length, int timeout_msec)
+{
+	struct cfg_write_pkg request = {
+		.header = tb_cfg_make_header(route),
+		.addr = {
+			.seq = 1,
+			.port = port,
+			.space = TB_CFG_PORT,
+			.offset = offset,
+			.length = length,
+		},
+	};
+	struct tb_cfg_request *req;
+	struct cfg_read_pkg reply;
+	struct tb_cfg_result res;
+
+	memcpy(&request.data, buffer, length * 4);
+
+	req = tb_cfg_request_alloc();
+	if (!req)
+		return -ENOMEM;
+
+	req->match = dma_port_match;
+	req->copy = dma_port_copy;
+	req->request = &request;
+	req->request_size = 12 + 4 * length;
+	req->request_type = TB_CFG_PKG_WRITE;
+	req->response = &reply;
+	req->response_size = sizeof(reply);
+	req->response_type = TB_CFG_PKG_WRITE;
+
+	res = tb_cfg_request_sync(ctl, req, timeout_msec);
+
+	tb_cfg_request_put(req);
+
+	return res.err;
+}
+
+static int dma_find_port(struct tb_switch *sw)
+{
+	int port, ret;
+	u32 type;
+
+	/*
+	 * The DMA (NHI) port is either 3 or 5 depending on the
+	 * controller. Try both starting from 5 which is more common.
+	 */
+	port = 5;
+	ret = dma_port_read(sw->tb->ctl, &type, tb_route(sw), port, 2, 1,
+			    DMA_PORT_TIMEOUT);
+	if (!ret && (type & 0xffffff) == TB_TYPE_NHI)
+		return port;
+
+	port = 3;
+	ret = dma_port_read(sw->tb->ctl, &type, tb_route(sw), port, 2, 1,
+			    DMA_PORT_TIMEOUT);
+	if (!ret && (type & 0xffffff) == TB_TYPE_NHI)
+		return port;
+
+	return -ENODEV;
+}
+
+/**
+ * dma_port_alloc() - Finds DMA control port from a switch pointed by route
+ * @sw: Switch from where find the DMA port
+ *
+ * Function checks if the switch NHI port supports DMA configuration
+ * based mailbox capability and if it does, allocates and initializes
+ * DMA port structure. Returns %NULL if the capabity was not found.
+ *
+ * The DMA control port is functional also when the switch is in safe
+ * mode.
+ */
+struct tb_dma_port *dma_port_alloc(struct tb_switch *sw)
+{
+	struct tb_dma_port *dma;
+	int port;
+
+	port = dma_find_port(sw);
+	if (port < 0)
+		return NULL;
+
+	dma = kzalloc(sizeof(*dma), GFP_KERNEL);
+	if (!dma)
+		return NULL;
+
+	dma->buf = kmalloc_array(MAIL_DATA_DWORDS, sizeof(u32), GFP_KERNEL);
+	if (!dma->buf) {
+		kfree(dma);
+		return NULL;
+	}
+
+	dma->sw = sw;
+	dma->port = port;
+	dma->base = DMA_PORT_CAP;
+
+	return dma;
+}
+
+/**
+ * dma_port_free() - Release DMA control port structure
+ * @dma: DMA control port
+ */
+void dma_port_free(struct tb_dma_port *dma)
+{
+	if (dma) {
+		kfree(dma->buf);
+		kfree(dma);
+	}
+}
+
+static int dma_port_wait_for_completion(struct tb_dma_port *dma,
+					unsigned int timeout)
+{
+	unsigned long end = jiffies + msecs_to_jiffies(timeout);
+	struct tb_switch *sw = dma->sw;
+
+	do {
+		int ret;
+		u32 in;
+
+		ret = dma_port_read(sw->tb->ctl, &in, tb_route(sw), dma->port,
+				    dma->base + MAIL_IN, 1, 50);
+		if (ret) {
+			if (ret != -ETIMEDOUT)
+				return ret;
+		} else if (!(in & MAIL_IN_OP_REQUEST)) {
+			return 0;
+		}
+
+		usleep_range(50, 100);
+	} while (time_before(jiffies, end));
+
+	return -ETIMEDOUT;
+}
+
+static int status_to_errno(u32 status)
+{
+	switch (status & MAIL_OUT_STATUS_MASK) {
+	case MAIL_OUT_STATUS_COMPLETED:
+		return 0;
+	case MAIL_OUT_STATUS_ERR_AUTH:
+		return -EINVAL;
+	case MAIL_OUT_STATUS_ERR_ACCESS:
+		return -EACCES;
+	}
+
+	return -EIO;
+}
+
+static int dma_port_request(struct tb_dma_port *dma, u32 in,
+			    unsigned int timeout)
+{
+	struct tb_switch *sw = dma->sw;
+	u32 out;
+	int ret;
+
+	ret = dma_port_write(sw->tb->ctl, &in, tb_route(sw), dma->port,
+			     dma->base + MAIL_IN, 1, DMA_PORT_TIMEOUT);
+	if (ret)
+		return ret;
+
+	ret = dma_port_wait_for_completion(dma, timeout);
+	if (ret)
+		return ret;
+
+	ret = dma_port_read(sw->tb->ctl, &out, tb_route(sw), dma->port,
+			    dma->base + MAIL_OUT, 1, DMA_PORT_TIMEOUT);
+	if (ret)
+		return ret;
+
+	return status_to_errno(out);
+}
+
+static int dma_port_flash_read_block(struct tb_dma_port *dma, u32 address,
+				     void *buf, u32 size)
+{
+	struct tb_switch *sw = dma->sw;
+	u32 in, dwaddress, dwords;
+	int ret;
+
+	dwaddress = address / 4;
+	dwords = size / 4;
+
+	in = MAIL_IN_CMD_FLASH_READ << MAIL_IN_CMD_SHIFT;
+	if (dwords < MAIL_DATA_DWORDS)
+		in |= (dwords << MAIL_IN_DWORDS_SHIFT) & MAIL_IN_DWORDS_MASK;
+	in |= (dwaddress << MAIL_IN_ADDRESS_SHIFT) & MAIL_IN_ADDRESS_MASK;
+	in |= MAIL_IN_OP_REQUEST;
+
+	ret = dma_port_request(dma, in, DMA_PORT_TIMEOUT);
+	if (ret)
+		return ret;
+
+	return dma_port_read(sw->tb->ctl, buf, tb_route(sw), dma->port,
+			     dma->base + MAIL_DATA, dwords, DMA_PORT_TIMEOUT);
+}
+
+static int dma_port_flash_write_block(struct tb_dma_port *dma, u32 address,
+				      const void *buf, u32 size)
+{
+	struct tb_switch *sw = dma->sw;
+	u32 in, dwaddress, dwords;
+	int ret;
+
+	dwords = size / 4;
+
+	/* Write the block to MAIL_DATA registers */
+	ret = dma_port_write(sw->tb->ctl, buf, tb_route(sw), dma->port,
+			    dma->base + MAIL_DATA, dwords, DMA_PORT_TIMEOUT);
+
+	in = MAIL_IN_CMD_FLASH_WRITE << MAIL_IN_CMD_SHIFT;
+
+	/* CSS header write is always done to the same magic address */
+	if (address >= DMA_PORT_CSS_ADDRESS) {
+		dwaddress = DMA_PORT_CSS_ADDRESS;
+		in |= MAIL_IN_CSS;
+	} else {
+		dwaddress = address / 4;
+	}
+
+	in |= ((dwords - 1) << MAIL_IN_DWORDS_SHIFT) & MAIL_IN_DWORDS_MASK;
+	in |= (dwaddress << MAIL_IN_ADDRESS_SHIFT) & MAIL_IN_ADDRESS_MASK;
+	in |= MAIL_IN_OP_REQUEST;
+
+	return dma_port_request(dma, in, DMA_PORT_TIMEOUT);
+}
+
+/**
+ * dma_port_flash_read() - Read from active flash region
+ * @dma: DMA control port
+ * @address: Address relative to the start of active region
+ * @buf: Buffer where the data is read
+ * @size: Size of the buffer
+ */
+int dma_port_flash_read(struct tb_dma_port *dma, unsigned int address,
+			void *buf, size_t size)
+{
+	unsigned int retries = DMA_PORT_RETRIES;
+	unsigned int offset;
+
+	offset = address & 3;
+	address = address & ~3;
+
+	do {
+		u32 nbytes = min_t(u32, size, MAIL_DATA_DWORDS * 4);
+		int ret;
+
+		ret = dma_port_flash_read_block(dma, address, dma->buf,
+						ALIGN(nbytes, 4));
+		if (ret) {
+			if (ret == -ETIMEDOUT) {
+				if (retries--)
+					continue;
+				ret = -EIO;
+			}
+			return ret;
+		}
+
+		memcpy(buf, dma->buf + offset, nbytes);
+
+		size -= nbytes;
+		address += nbytes;
+		buf += nbytes;
+	} while (size > 0);
+
+	return 0;
+}
+
+/**
+ * dma_port_flash_write() - Write to non-active flash region
+ * @dma: DMA control port
+ * @address: Address relative to the start of non-active region
+ * @buf: Data to write
+ * @size: Size of the buffer
+ *
+ * Writes block of data to the non-active flash region of the switch. If
+ * the address is given as %DMA_PORT_CSS_ADDRESS the block is written
+ * using CSS command.
+ */
+int dma_port_flash_write(struct tb_dma_port *dma, unsigned int address,
+			 const void *buf, size_t size)
+{
+	unsigned int retries = DMA_PORT_RETRIES;
+	unsigned int offset;
+
+	if (address >= DMA_PORT_CSS_ADDRESS) {
+		offset = 0;
+		if (size > DMA_PORT_CSS_MAX_SIZE)
+			return -E2BIG;
+	} else {
+		offset = address & 3;
+		address = address & ~3;
+	}
+
+	do {
+		u32 nbytes = min_t(u32, size, MAIL_DATA_DWORDS * 4);
+		int ret;
+
+		memcpy(dma->buf + offset, buf, nbytes);
+
+		ret = dma_port_flash_write_block(dma, address, buf, nbytes);
+		if (ret) {
+			if (ret == -ETIMEDOUT) {
+				if (retries--)
+					continue;
+				ret = -EIO;
+			}
+			return ret;
+		}
+
+		size -= nbytes;
+		address += nbytes;
+		buf += nbytes;
+	} while (size > 0);
+
+	return 0;
+}
+
+/**
+ * dma_port_flash_update_auth() - Starts flash authenticate cycle
+ * @dma: DMA control port
+ *
+ * Starts the flash update authentication cycle. If the image in the
+ * non-active area was valid, the switch starts upgrade process where
+ * active and non-active area get swapped in the end. Caller should call
+ * dma_port_flash_update_auth_status() to get status of this command.
+ * This is because if the switch in question is root switch the
+ * thunderbolt host controller gets reset as well.
+ */
+int dma_port_flash_update_auth(struct tb_dma_port *dma)
+{
+	u32 in;
+
+	in = MAIL_IN_CMD_FLASH_UPDATE_AUTH << MAIL_IN_CMD_SHIFT;
+	in |= MAIL_IN_OP_REQUEST;
+
+	return dma_port_request(dma, in, 150);
+}
+
+/**
+ * dma_port_flash_update_auth_status() - Reads status of update auth command
+ * @dma: DMA control port
+ * @status: Status code of the operation
+ *
+ * The function checks if there is status available from the last update
+ * auth command. Returns %0 if there is no status and no further
+ * action is required. If there is status, %1 is returned instead and
+ * @status holds the failure code.
+ *
+ * Negative return means there was an error reading status from the
+ * switch.
+ */
+int dma_port_flash_update_auth_status(struct tb_dma_port *dma, u32 *status)
+{
+	struct tb_switch *sw = dma->sw;
+	u32 out, cmd;
+	int ret;
+
+	ret = dma_port_read(sw->tb->ctl, &out, tb_route(sw), dma->port,
+			    dma->base + MAIL_OUT, 1, DMA_PORT_TIMEOUT);
+	if (ret)
+		return ret;
+
+	/* Check if the status relates to flash update auth */
+	cmd = (out & MAIL_OUT_STATUS_CMD_MASK) >> MAIL_OUT_STATUS_CMD_SHIFT;
+	if (cmd == MAIL_IN_CMD_FLASH_UPDATE_AUTH) {
+		if (status)
+			*status = out & MAIL_OUT_STATUS_MASK;
+
+		/* Reset is needed in any case */
+		return 1;
+	}
+
+	return 0;
+}
+
+/**
+ * dma_port_power_cycle() - Power cycles the switch
+ * @dma: DMA control port
+ *
+ * Triggers power cycle to the switch.
+ */
+int dma_port_power_cycle(struct tb_dma_port *dma)
+{
+	u32 in;
+
+	in = MAIL_IN_CMD_POWER_CYCLE << MAIL_IN_CMD_SHIFT;
+	in |= MAIL_IN_OP_REQUEST;
+
+	return dma_port_request(dma, in, 150);
+}
diff --git a/drivers/thunderbolt/dma_port.h b/drivers/thunderbolt/dma_port.h
new file mode 100644
index 000000000000..c4a69e0fbff7
--- /dev/null
+++ b/drivers/thunderbolt/dma_port.h
@@ -0,0 +1,34 @@
+/*
+ * Thunderbolt DMA configuration based mailbox support
+ *
+ * Copyright (C) 2017, Intel Corporation
+ * Authors: Michael Jamet <michael.jamet@intel.com>
+ *          Mika Westerberg <mika.westerberg@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef DMA_PORT_H_
+#define DMA_PORT_H_
+
+#include "tb.h"
+
+struct tb_switch;
+struct tb_dma_port;
+
+#define DMA_PORT_CSS_ADDRESS		0x3fffff
+#define DMA_PORT_CSS_MAX_SIZE		SZ_128
+
+struct tb_dma_port *dma_port_alloc(struct tb_switch *sw);
+void dma_port_free(struct tb_dma_port *dma);
+int dma_port_flash_read(struct tb_dma_port *dma, unsigned int address,
+			void *buf, size_t size);
+int dma_port_flash_update_auth(struct tb_dma_port *dma);
+int dma_port_flash_update_auth_status(struct tb_dma_port *dma, u32 *status);
+int dma_port_flash_write(struct tb_dma_port *dma, unsigned int address,
+			 const void *buf, size_t size);
+int dma_port_power_cycle(struct tb_dma_port *dma);
+
+#endif
diff --git a/drivers/thunderbolt/eeprom.c b/drivers/thunderbolt/eeprom.c
index d40a5f07fc4c..996c6e29c8ad 100644
--- a/drivers/thunderbolt/eeprom.c
+++ b/drivers/thunderbolt/eeprom.c
@@ -429,6 +429,50 @@ err:
 	return -EINVAL;
 }
 
+static int tb_drom_copy_nvm(struct tb_switch *sw, u16 *size)
+{
+	u32 drom_offset;
+	int ret;
+
+	if (!sw->dma_port)
+		return -ENODEV;
+
+	ret = tb_sw_read(sw, &drom_offset, TB_CFG_SWITCH,
+			 sw->cap_plug_events + 12, 1);
+	if (ret)
+		return ret;
+
+	if (!drom_offset)
+		return -ENODEV;
+
+	ret = dma_port_flash_read(sw->dma_port, drom_offset + 14, size,
+				  sizeof(*size));
+	if (ret)
+		return ret;
+
+	/* Size includes CRC8 + UID + CRC32 */
+	*size += 1 + 8 + 4;
+	sw->drom = kzalloc(*size, GFP_KERNEL);
+	if (!sw->drom)
+		return -ENOMEM;
+
+	ret = dma_port_flash_read(sw->dma_port, drom_offset, sw->drom, *size);
+	if (ret)
+		goto err_free;
+
+	/*
+	 * Read UID from the minimal DROM because the one in NVM is just
+	 * a placeholder.
+	 */
+	tb_drom_read_uid_only(sw, &sw->uid);
+	return 0;
+
+err_free:
+	kfree(sw->drom);
+	sw->drom = NULL;
+	return ret;
+}
+
 /**
  * tb_drom_read - copy drom to sw->drom and parse it
  */
@@ -450,6 +494,10 @@ int tb_drom_read(struct tb_switch *sw)
 		if (tb_drom_copy_efi(sw, &size) == 0)
 			goto parse;
 
+		/* Non-Apple hardware has the DROM as part of NVM */
+		if (tb_drom_copy_nvm(sw, &size) == 0)
+			goto parse;
+
 		/*
 		 * The root switch contains only a dummy drom (header only,
 		 * no entries). Hardcode the configuration here.
@@ -510,7 +558,8 @@ parse:
 			header->uid_crc8, crc);
 		goto err;
 	}
-	sw->uid = header->uid;
+	if (!sw->uid)
+		sw->uid = header->uid;
 	sw->vendor = header->vendor_id;
 	sw->device = header->model_id;
 
diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 6384061100b0..4b47e0999cda 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -377,6 +377,8 @@ static void tb_switch_release(struct device *dev)
 {
 	struct tb_switch *sw = tb_to_switch(dev);
 
+	dma_port_free(sw->dma_port);
+
 	kfree(sw->uuid);
 	kfree(sw->device_name);
 	kfree(sw->vendor_name);
@@ -570,6 +572,25 @@ static void tb_switch_set_uuid(struct tb_switch *sw)
 	sw->uuid = kmemdup(uuid, sizeof(uuid), GFP_KERNEL);
 }
 
+static void tb_switch_add_dma_port(struct tb_switch *sw)
+{
+	switch (sw->generation) {
+	case 3:
+		break;
+
+	case 2:
+		/* Only root switch can be upgraded */
+		if (tb_route(sw))
+			return;
+		break;
+
+	default:
+		return;
+	}
+
+	sw->dma_port = dma_port_alloc(sw);
+}
+
 /**
  * tb_switch_add() - Add a switch to the domain
  * @sw: Switch to add
@@ -586,6 +607,15 @@ int tb_switch_add(struct tb_switch *sw)
 {
 	int i, ret;
 
+	/*
+	 * Initialize DMA control port now before we read DROM. Recent
+	 * host controllers have more complete DROM on NVM that includes
+	 * vendor and model identification strings which we then expose
+	 * to the userspace. NVM can be accessed through DMA
+	 * configuration based mailbox.
+	 */
+	tb_switch_add_dma_port(sw);
+
 	/* read drom */
 	ret = tb_drom_read(sw);
 	if (ret) {
diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index 39d24dff82c5..31521c531715 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -12,12 +12,16 @@
 
 #include "tb_regs.h"
 #include "ctl.h"
+#include "dma_port.h"
 
 /**
  * struct tb_switch - a thunderbolt switch
  * @dev: Device for the switch
  * @config: Switch configuration
  * @ports: Ports in this switch
+ * @dma_port: If the switch has port supporting DMA configuration based
+ *	      mailbox this will hold the pointer to that (%NULL
+ *	      otherwise).
  * @tb: Pointer to the domain the switch belongs to
  * @uid: Unique ID of the switch
  * @uuid: UUID of the switch (or %NULL if not supported)
@@ -34,6 +38,7 @@ struct tb_switch {
 	struct device dev;
 	struct tb_regs_switch_header config;
 	struct tb_port *ports;
+	struct tb_dma_port *dma_port;
 	struct tb *tb;
 	u64 uid;
 	uuid_be *uuid;