thunderbolt: Add initial support for USB4

USB4 is the public specification based on Thunderbolt 3 protocol. There
are some differences in register layouts and flows. In addition to PCIe
and DP tunneling, USB4 supports tunneling of USB 3.x. USB4 is also
backward compatible with Thunderbolt 3 (and older generations but the
spec only talks about 3rd generation). USB4 compliant devices can be
identified by checking USB4 version field in router configuration space.

This patch adds initial support for USB4 compliant hosts and devices
which enables following features provided by the existing functionality
in the driver:

  - PCIe tunneling
  - Display Port tunneling
  - Host and device NVM firmware upgrade
  - P2P networking

This brings the USB4 support to the same level that we already have for
Thunderbolt 1, 2 and 3 devices.

Note the spec talks about host and device "routers" but in the driver we
still use term "switch" in most places. Both can be used interchangeably.

Co-developed-by: Rajmohan Mani <rajmohan.mani@intel.com>
Signed-off-by: Rajmohan Mani <rajmohan.mani@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Link: https://lore.kernel.org/r/20191217123345.31850-5-mika.westerberg@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 724 insertions, 0 deletions

diff --git a/drivers/thunderbolt/usb4.c b/drivers/thunderbolt/usb4.c
new file mode 100644
index 000000000000..b84c74346d2b
--- /dev/null
+++ b/drivers/thunderbolt/usb4.c
@@ -0,0 +1,724 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB4 specific functionality
+ *
+ * Copyright (C) 2019, Intel Corporation
+ * Authors: Mika Westerberg <mika.westerberg@linux.intel.com>
+ *	    Rajmohan Mani <rajmohan.mani@intel.com>
+ */
+
+#include <linux/delay.h>
+#include <linux/ktime.h>
+
+#include "tb.h"
+
+#define USB4_DATA_DWORDS		16
+#define USB4_DATA_RETRIES		3
+
+enum usb4_switch_op {
+	USB4_SWITCH_OP_QUERY_DP_RESOURCE = 0x10,
+	USB4_SWITCH_OP_ALLOC_DP_RESOURCE = 0x11,
+	USB4_SWITCH_OP_DEALLOC_DP_RESOURCE = 0x12,
+	USB4_SWITCH_OP_NVM_WRITE = 0x20,
+	USB4_SWITCH_OP_NVM_AUTH = 0x21,
+	USB4_SWITCH_OP_NVM_READ = 0x22,
+	USB4_SWITCH_OP_NVM_SET_OFFSET = 0x23,
+	USB4_SWITCH_OP_DROM_READ = 0x24,
+	USB4_SWITCH_OP_NVM_SECTOR_SIZE = 0x25,
+};
+
+#define USB4_NVM_READ_OFFSET_MASK	GENMASK(23, 2)
+#define USB4_NVM_READ_OFFSET_SHIFT	2
+#define USB4_NVM_READ_LENGTH_MASK	GENMASK(27, 24)
+#define USB4_NVM_READ_LENGTH_SHIFT	24
+
+#define USB4_NVM_SET_OFFSET_MASK	USB4_NVM_READ_OFFSET_MASK
+#define USB4_NVM_SET_OFFSET_SHIFT	USB4_NVM_READ_OFFSET_SHIFT
+
+#define USB4_DROM_ADDRESS_MASK		GENMASK(14, 2)
+#define USB4_DROM_ADDRESS_SHIFT		2
+#define USB4_DROM_SIZE_MASK		GENMASK(19, 15)
+#define USB4_DROM_SIZE_SHIFT		15
+
+#define USB4_NVM_SECTOR_SIZE_MASK	GENMASK(23, 0)
+
+typedef int (*read_block_fn)(struct tb_switch *, unsigned int, void *, size_t);
+typedef int (*write_block_fn)(struct tb_switch *, const void *, size_t);
+
+static int usb4_switch_wait_for_bit(struct tb_switch *sw, u32 offset, u32 bit,
+				    u32 value, int timeout_msec)
+{
+	ktime_t timeout = ktime_add_ms(ktime_get(), timeout_msec);
+
+	do {
+		u32 val;
+		int ret;
+
+		ret = tb_sw_read(sw, &val, TB_CFG_SWITCH, offset, 1);
+		if (ret)
+			return ret;
+
+		if ((val & bit) == value)
+			return 0;
+
+		usleep_range(50, 100);
+	} while (ktime_before(ktime_get(), timeout));
+
+	return -ETIMEDOUT;
+}
+
+static int usb4_switch_op_read_data(struct tb_switch *sw, void *data,
+				    size_t dwords)
+{
+	if (dwords > USB4_DATA_DWORDS)
+		return -EINVAL;
+
+	return tb_sw_read(sw, data, TB_CFG_SWITCH, ROUTER_CS_9, dwords);
+}
+
+static int usb4_switch_op_write_data(struct tb_switch *sw, const void *data,
+				     size_t dwords)
+{
+	if (dwords > USB4_DATA_DWORDS)
+		return -EINVAL;
+
+	return tb_sw_write(sw, data, TB_CFG_SWITCH, ROUTER_CS_9, dwords);
+}
+
+static int usb4_switch_op_read_metadata(struct tb_switch *sw, u32 *metadata)
+{
+	return tb_sw_read(sw, metadata, TB_CFG_SWITCH, ROUTER_CS_25, 1);
+}
+
+static int usb4_switch_op_write_metadata(struct tb_switch *sw, u32 metadata)
+{
+	return tb_sw_write(sw, &metadata, TB_CFG_SWITCH, ROUTER_CS_25, 1);
+}
+
+static int usb4_switch_do_read_data(struct tb_switch *sw, u16 address,
+	void *buf, size_t size, read_block_fn read_block)
+{
+	unsigned int retries = USB4_DATA_RETRIES;
+	unsigned int offset;
+
+	offset = address & 3;
+	address = address & ~3;
+
+	do {
+		size_t nbytes = min_t(size_t, size, USB4_DATA_DWORDS * 4);
+		unsigned int dwaddress, dwords;
+		u8 data[USB4_DATA_DWORDS * 4];
+		int ret;
+
+		dwaddress = address / 4;
+		dwords = ALIGN(nbytes, 4) / 4;
+
+		ret = read_block(sw, dwaddress, data, dwords);
+		if (ret) {
+			if (ret == -ETIMEDOUT) {
+				if (retries--)
+					continue;
+				ret = -EIO;
+			}
+			return ret;
+		}
+
+		memcpy(buf, data + offset, nbytes);
+
+		size -= nbytes;
+		address += nbytes;
+		buf += nbytes;
+	} while (size > 0);
+
+	return 0;
+}
+
+static int usb4_switch_do_write_data(struct tb_switch *sw, u16 address,
+	const void *buf, size_t size, write_block_fn write_next_block)
+{
+	unsigned int retries = USB4_DATA_RETRIES;
+	unsigned int offset;
+
+	offset = address & 3;
+	address = address & ~3;
+
+	do {
+		u32 nbytes = min_t(u32, size, USB4_DATA_DWORDS * 4);
+		u8 data[USB4_DATA_DWORDS * 4];
+		int ret;
+
+		memcpy(data + offset, buf, nbytes);
+
+		ret = write_next_block(sw, data, nbytes / 4);
+		if (ret) {
+			if (ret == -ETIMEDOUT) {
+				if (retries--)
+					continue;
+				ret = -EIO;
+			}
+			return ret;
+		}
+
+		size -= nbytes;
+		address += nbytes;
+		buf += nbytes;
+	} while (size > 0);
+
+	return 0;
+}
+
+static int usb4_switch_op(struct tb_switch *sw, u16 opcode, u8 *status)
+{
+	u32 val;
+	int ret;
+
+	val = opcode | ROUTER_CS_26_OV;
+	ret = tb_sw_write(sw, &val, TB_CFG_SWITCH, ROUTER_CS_26, 1);
+	if (ret)
+		return ret;
+
+	ret = usb4_switch_wait_for_bit(sw, ROUTER_CS_26, ROUTER_CS_26_OV, 0, 500);
+	if (ret)
+		return ret;
+
+	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH, ROUTER_CS_26, 1);
+	if (val & ROUTER_CS_26_ONS)
+		return -EOPNOTSUPP;
+
+	*status = (val & ROUTER_CS_26_STATUS_MASK) >> ROUTER_CS_26_STATUS_SHIFT;
+	return 0;
+}
+
+/**
+ * usb4_switch_setup() - Additional setup for USB4 device
+ * @sw: USB4 router to setup
+ *
+ * USB4 routers need additional settings in order to enable all the
+ * tunneling. This function enables USB and PCIe tunneling if it can be
+ * enabled (e.g the parent switch also supports them). If USB tunneling
+ * is not available for some reason (like that there is Thunderbolt 3
+ * switch upstream) then the internal xHCI controller is enabled
+ * instead.
+ */
+int usb4_switch_setup(struct tb_switch *sw)
+{
+	struct tb_switch *parent;
+	bool tbt3, xhci;
+	u32 val = 0;
+	int ret;
+
+	if (!tb_route(sw))
+		return 0;
+
+	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH, ROUTER_CS_6, 1);
+	if (ret)
+		return ret;
+
+	xhci = val & ROUTER_CS_6_HCI;
+	tbt3 = !(val & ROUTER_CS_6_TNS);
+
+	tb_sw_dbg(sw, "TBT3 support: %s, xHCI: %s\n",
+		  tbt3 ? "yes" : "no", xhci ? "yes" : "no");
+
+	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH, ROUTER_CS_5, 1);
+	if (ret)
+		return ret;
+
+	parent = tb_switch_parent(sw);
+
+	/* Only enable PCIe tunneling if the parent router supports it */
+	if (tb_switch_find_port(parent, TB_TYPE_PCIE_DOWN)) {
+		val |= ROUTER_CS_5_PTO;
+		/* xHCI can be enabled if PCIe tunneling is supported */
+		if (xhci & ROUTER_CS_6_HCI)
+			val |= ROUTER_CS_5_HCO;
+	}
+
+	/* TBT3 supported by the CM */
+	val |= ROUTER_CS_5_C3S;
+	/* Tunneling configuration is ready now */
+	val |= ROUTER_CS_5_CV;
+
+	ret = tb_sw_write(sw, &val, TB_CFG_SWITCH, ROUTER_CS_5, 1);
+	if (ret)
+		return ret;
+
+	return usb4_switch_wait_for_bit(sw, ROUTER_CS_6, ROUTER_CS_6_CR,
+					ROUTER_CS_6_CR, 50);
+}
+
+/**
+ * usb4_switch_read_uid() - Read UID from USB4 router
+ * @sw: USB4 router
+ *
+ * Reads 64-bit UID from USB4 router config space.
+ */
+int usb4_switch_read_uid(struct tb_switch *sw, u64 *uid)
+{
+	return tb_sw_read(sw, uid, TB_CFG_SWITCH, ROUTER_CS_7, 2);
+}
+
+static int usb4_switch_drom_read_block(struct tb_switch *sw,
+				       unsigned int dwaddress, void *buf,
+				       size_t dwords)
+{
+	u8 status = 0;
+	u32 metadata;
+	int ret;
+
+	metadata = (dwords << USB4_DROM_SIZE_SHIFT) & USB4_DROM_SIZE_MASK;
+	metadata |= (dwaddress << USB4_DROM_ADDRESS_SHIFT) &
+		USB4_DROM_ADDRESS_MASK;
+
+	ret = usb4_switch_op_write_metadata(sw, metadata);
+	if (ret)
+		return ret;
+
+	ret = usb4_switch_op(sw, USB4_SWITCH_OP_DROM_READ, &status);
+	if (ret)
+		return ret;
+
+	if (status)
+		return -EIO;
+
+	return usb4_switch_op_read_data(sw, buf, dwords);
+}
+
+/**
+ * usb4_switch_drom_read() - Read arbitrary bytes from USB4 router DROM
+ * @sw: USB4 router
+ *
+ * Uses USB4 router operations to read router DROM. For devices this
+ * should always work but for hosts it may return %-EOPNOTSUPP in which
+ * case the host router does not have DROM.
+ */
+int usb4_switch_drom_read(struct tb_switch *sw, unsigned int address, void *buf,
+			  size_t size)
+{
+	return usb4_switch_do_read_data(sw, address, buf, size,
+					usb4_switch_drom_read_block);
+}
+
+static int usb4_set_port_configured(struct tb_port *port, bool configured)
+{
+	int ret;
+	u32 val;
+
+	ret = tb_port_read(port, &val, TB_CFG_PORT,
+			   port->cap_usb4 + PORT_CS_19, 1);
+	if (ret)
+		return ret;
+
+	if (configured)
+		val |= PORT_CS_19_PC;
+	else
+		val &= ~PORT_CS_19_PC;
+
+	return tb_port_write(port, &val, TB_CFG_PORT,
+			     port->cap_usb4 + PORT_CS_19, 1);
+}
+
+/**
+ * usb4_switch_configure_link() - Set upstream USB4 link configured
+ * @sw: USB4 router
+ *
+ * Sets the upstream USB4 link to be configured for power management
+ * purposes.
+ */
+int usb4_switch_configure_link(struct tb_switch *sw)
+{
+	struct tb_port *up;
+
+	if (!tb_route(sw))
+		return 0;
+
+	up = tb_upstream_port(sw);
+	return usb4_set_port_configured(up, true);
+}
+
+/**
+ * usb4_switch_unconfigure_link() - Un-set upstream USB4 link configuration
+ * @sw: USB4 router
+ *
+ * Reverse of usb4_switch_configure_link().
+ */
+void usb4_switch_unconfigure_link(struct tb_switch *sw)
+{
+	struct tb_port *up;
+
+	if (sw->is_unplugged || !tb_route(sw))
+		return;
+
+	up = tb_upstream_port(sw);
+	usb4_set_port_configured(up, false);
+}
+
+/**
+ * usb4_switch_lane_bonding_possible() - Are conditions met for lane bonding
+ * @sw: USB4 router
+ *
+ * Checks whether conditions are met so that lane bonding can be
+ * established with the upstream router. Call only for device routers.
+ */
+bool usb4_switch_lane_bonding_possible(struct tb_switch *sw)
+{
+	struct tb_port *up;
+	int ret;
+	u32 val;
+
+	up = tb_upstream_port(sw);
+	ret = tb_port_read(up, &val, TB_CFG_PORT, up->cap_usb4 + PORT_CS_18, 1);
+	if (ret)
+		return false;
+
+	return !!(val & PORT_CS_18_BE);
+}
+
+/**
+ * usb4_switch_set_sleep() - Prepare the router to enter sleep
+ * @sw: USB4 router
+ *
+ * Enables wakes and sets sleep bit for the router. Returns when the
+ * router sleep ready bit has been asserted.
+ */
+int usb4_switch_set_sleep(struct tb_switch *sw)
+{
+	int ret;
+	u32 val;
+
+	/* Set sleep bit and wait for sleep ready to be asserted */
+	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH, ROUTER_CS_5, 1);
+	if (ret)
+		return ret;
+
+	val |= ROUTER_CS_5_SLP;
+
+	ret = tb_sw_write(sw, &val, TB_CFG_SWITCH, ROUTER_CS_5, 1);
+	if (ret)
+		return ret;
+
+	return usb4_switch_wait_for_bit(sw, ROUTER_CS_6, ROUTER_CS_6_SLPR,
+					ROUTER_CS_6_SLPR, 500);
+}
+
+/**
+ * usb4_switch_nvm_sector_size() - Return router NVM sector size
+ * @sw: USB4 router
+ *
+ * If the router supports NVM operations this function returns the NVM
+ * sector size in bytes. If NVM operations are not supported returns
+ * %-EOPNOTSUPP.
+ */
+int usb4_switch_nvm_sector_size(struct tb_switch *sw)
+{
+	u32 metadata;
+	u8 status;
+	int ret;
+
+	ret = usb4_switch_op(sw, USB4_SWITCH_OP_NVM_SECTOR_SIZE, &status);
+	if (ret)
+		return ret;
+
+	if (status)
+		return status == 0x2 ? -EOPNOTSUPP : -EIO;
+
+	ret = usb4_switch_op_read_metadata(sw, &metadata);
+	if (ret)
+		return ret;
+
+	return metadata & USB4_NVM_SECTOR_SIZE_MASK;
+}
+
+static int usb4_switch_nvm_read_block(struct tb_switch *sw,
+	unsigned int dwaddress, void *buf, size_t dwords)
+{
+	u8 status = 0;
+	u32 metadata;
+	int ret;
+
+	metadata = (dwords << USB4_NVM_READ_LENGTH_SHIFT) &
+		   USB4_NVM_READ_LENGTH_MASK;
+	metadata |= (dwaddress << USB4_NVM_READ_OFFSET_SHIFT) &
+		   USB4_NVM_READ_OFFSET_MASK;
+
+	ret = usb4_switch_op_write_metadata(sw, metadata);
+	if (ret)
+		return ret;
+
+	ret = usb4_switch_op(sw, USB4_SWITCH_OP_NVM_READ, &status);
+	if (ret)
+		return ret;
+
+	if (status)
+		return -EIO;
+
+	return usb4_switch_op_read_data(sw, buf, dwords);
+}
+
+/**
+ * usb4_switch_nvm_read() - Read arbitrary bytes from router NVM
+ * @sw: USB4 router
+ * @address: Starting address in bytes
+ * @buf: Read data is placed here
+ * @size: How many bytes to read
+ *
+ * Reads NVM contents of the router. If NVM is not supported returns
+ * %-EOPNOTSUPP.
+ */
+int usb4_switch_nvm_read(struct tb_switch *sw, unsigned int address, void *buf,
+			 size_t size)
+{
+	return usb4_switch_do_read_data(sw, address, buf, size,
+					usb4_switch_nvm_read_block);
+}
+
+static int usb4_switch_nvm_set_offset(struct tb_switch *sw,
+				      unsigned int address)
+{
+	u32 metadata, dwaddress;
+	u8 status = 0;
+	int ret;
+
+	dwaddress = address / 4;
+	metadata = (dwaddress << USB4_NVM_SET_OFFSET_SHIFT) &
+		   USB4_NVM_SET_OFFSET_MASK;
+
+	ret = usb4_switch_op_write_metadata(sw, metadata);
+	if (ret)
+		return ret;
+
+	ret = usb4_switch_op(sw, USB4_SWITCH_OP_NVM_SET_OFFSET, &status);
+	if (ret)
+		return ret;
+
+	return status ? -EIO : 0;
+}
+
+static int usb4_switch_nvm_write_next_block(struct tb_switch *sw,
+					    const void *buf, size_t dwords)
+{
+	u8 status;
+	int ret;
+
+	ret = usb4_switch_op_write_data(sw, buf, dwords);
+	if (ret)
+		return ret;
+
+	ret = usb4_switch_op(sw, USB4_SWITCH_OP_NVM_WRITE, &status);
+	if (ret)
+		return ret;
+
+	return status ? -EIO : 0;
+}
+
+/**
+ * usb4_switch_nvm_write() - Write to the router NVM
+ * @sw: USB4 router
+ * @address: Start address where to write in bytes
+ * @buf: Pointer to the data to write
+ * @size: Size of @buf in bytes
+ *
+ * Writes @buf to the router NVM using USB4 router operations. If NVM
+ * write is not supported returns %-EOPNOTSUPP.
+ */
+int usb4_switch_nvm_write(struct tb_switch *sw, unsigned int address,
+			  const void *buf, size_t size)
+{
+	int ret;
+
+	ret = usb4_switch_nvm_set_offset(sw, address);
+	if (ret)
+		return ret;
+
+	return usb4_switch_do_write_data(sw, address, buf, size,
+					 usb4_switch_nvm_write_next_block);
+}
+
+/**
+ * usb4_switch_nvm_authenticate() - Authenticate new NVM
+ * @sw: USB4 router
+ *
+ * After the new NVM has been written via usb4_switch_nvm_write(), this
+ * function triggers NVM authentication process. If the authentication
+ * is successful the router is power cycled and the new NVM starts
+ * running. In case of failure returns negative errno.
+ */
+int usb4_switch_nvm_authenticate(struct tb_switch *sw)
+{
+	u8 status = 0;
+	int ret;
+
+	ret = usb4_switch_op(sw, USB4_SWITCH_OP_NVM_AUTH, &status);
+	if (ret)
+		return ret;
+
+	switch (status) {
+	case 0x0:
+		tb_sw_dbg(sw, "NVM authentication successful\n");
+		return 0;
+	case 0x1:
+		return -EINVAL;
+	case 0x2:
+		return -EAGAIN;
+	case 0x3:
+		return -EOPNOTSUPP;
+	default:
+		return -EIO;
+	}
+}
+
+/**
+ * usb4_switch_query_dp_resource() - Query availability of DP IN resource
+ * @sw: USB4 router
+ * @in: DP IN adapter
+ *
+ * For DP tunneling this function can be used to query availability of
+ * DP IN resource. Returns true if the resource is available for DP
+ * tunneling, false otherwise.
+ */
+bool usb4_switch_query_dp_resource(struct tb_switch *sw, struct tb_port *in)
+{
+	u8 status;
+	int ret;
+
+	ret = usb4_switch_op_write_metadata(sw, in->port);
+	if (ret)
+		return false;
+
+	ret = usb4_switch_op(sw, USB4_SWITCH_OP_QUERY_DP_RESOURCE, &status);
+	/*
+	 * If DP resource allocation is not supported assume it is
+	 * always available.
+	 */
+	if (ret == -EOPNOTSUPP)
+		return true;
+	else if (ret)
+		return false;
+
+	return !status;
+}
+
+/**
+ * usb4_switch_alloc_dp_resource() - Allocate DP IN resource
+ * @sw: USB4 router
+ * @in: DP IN adapter
+ *
+ * Allocates DP IN resource for DP tunneling using USB4 router
+ * operations. If the resource was allocated returns %0. Otherwise
+ * returns negative errno, in particular %-EBUSY if the resource is
+ * already allocated.
+ */
+int usb4_switch_alloc_dp_resource(struct tb_switch *sw, struct tb_port *in)
+{
+	u8 status;
+	int ret;
+
+	ret = usb4_switch_op_write_metadata(sw, in->port);
+	if (ret)
+		return ret;
+
+	ret = usb4_switch_op(sw, USB4_SWITCH_OP_ALLOC_DP_RESOURCE, &status);
+	if (ret == -EOPNOTSUPP)
+		return 0;
+	else if (ret)
+		return ret;
+
+	return status ? -EBUSY : 0;
+}
+
+/**
+ * usb4_switch_dealloc_dp_resource() - Releases allocated DP IN resource
+ * @sw: USB4 router
+ * @in: DP IN adapter
+ *
+ * Releases the previously allocated DP IN resource.
+ */
+int usb4_switch_dealloc_dp_resource(struct tb_switch *sw, struct tb_port *in)
+{
+	u8 status;
+	int ret;
+
+	ret = usb4_switch_op_write_metadata(sw, in->port);
+	if (ret)
+		return ret;
+
+	ret = usb4_switch_op(sw, USB4_SWITCH_OP_DEALLOC_DP_RESOURCE, &status);
+	if (ret == -EOPNOTSUPP)
+		return 0;
+	else if (ret)
+		return ret;
+
+	return status ? -EIO : 0;
+}
+
+static int usb4_port_idx(const struct tb_switch *sw, const struct tb_port *port)
+{
+	struct tb_port *p;
+	int usb4_idx = 0;
+
+	/* Assume port is primary */
+	tb_switch_for_each_port(sw, p) {
+		if (!tb_port_is_null(p))
+			continue;
+		if (tb_is_upstream_port(p))
+			continue;
+		if (!p->link_nr) {
+			if (p == port)
+				break;
+			usb4_idx++;
+		}
+	}
+
+	return usb4_idx;
+}
+
+/**
+ * usb4_switch_map_pcie_down() - Map USB4 port to a PCIe downstream adapter
+ * @sw: USB4 router
+ * @port: USB4 port
+ *
+ * USB4 routers have direct mapping between USB4 ports and PCIe
+ * downstream adapters where the PCIe topology is extended. This
+ * function returns the corresponding downstream PCIe adapter or %NULL
+ * if no such mapping was possible.
+ */
+struct tb_port *usb4_switch_map_pcie_down(struct tb_switch *sw,
+					  const struct tb_port *port)
+{
+	int usb4_idx = usb4_port_idx(sw, port);
+	struct tb_port *p;
+	int pcie_idx = 0;
+
+	/* Find PCIe down port matching usb4_port */
+	tb_switch_for_each_port(sw, p) {
+		if (!tb_port_is_pcie_down(p))
+			continue;
+
+		if (pcie_idx == usb4_idx && !tb_pci_port_is_enabled(p))
+			return p;
+
+		pcie_idx++;
+	}
+
+	return NULL;
+}
+
+/**
+ * usb4_port_unlock() - Unlock USB4 downstream port
+ * @port: USB4 port to unlock
+ *
+ * Unlocks USB4 downstream port so that the connection manager can
+ * access the router below this port.
+ */
+int usb4_port_unlock(struct tb_port *port)
+{
+	int ret;
+	u32 val;
+
+	ret = tb_port_read(port, &val, TB_CFG_PORT, ADP_CS_4, 1);
+	if (ret)
+		return ret;
+
+	val &= ~ADP_CS_4_LCK;
+	return tb_port_write(port, &val, TB_CFG_PORT, ADP_CS_4, 1);
+}