linux/drivers/thunderbolt/switch.c

/*
 * Thunderbolt Cactus Ridge driver - switch/port utility functions
 *
 * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
 */

#include <linux/delay.h>
#include <linux/slab.h>

#include "tb.h"

/* Switch authorization from userspace is serialized by this lock */
static DEFINE_MUTEX(switch_lock);

/* port utility functions */

static const char *tb_port_type(struct tb_regs_port_header *port)
{
	switch (port->type >> 16) {
	case 0:
		switch ((u8) port->type) {
		case 0:
			return "Inactive";
		case 1:
			return "Port";
		case 2:
			return "NHI";
		default:
			return "unknown";
		}
	case 0x2:
		return "Ethernet";
	case 0x8:
		return "SATA";
	case 0xe:
		return "DP/HDMI";
	case 0x10:
		return "PCIe";
	case 0x20:
		return "USB";
	default:
		return "unknown";
	}
}

static void tb_dump_port(struct tb *tb, struct tb_regs_port_header *port)
{
	tb_info(tb,
		" Port %d: %x:%x (Revision: %d, TB Version: %d, Type: %s (%#x))\n",
		port->port_number, port->vendor_id, port->device_id,
		port->revision, port->thunderbolt_version, tb_port_type(port),
		port->type);
	tb_info(tb, "  Max hop id (in/out): %d/%d\n",
		port->max_in_hop_id, port->max_out_hop_id);
	tb_info(tb, "  Max counters: %d\n", port->max_counters);
	tb_info(tb, "  NFC Credits: %#x\n", port->nfc_credits);
}

/**
 * tb_port_state() - get connectedness state of a port
 *
 * The port must have a TB_CAP_PHY (i.e. it should be a real port).
 *
 * Return: Returns an enum tb_port_state on success or an error code on failure.
 */
static int tb_port_state(struct tb_port *port)
{
	struct tb_cap_phy phy;
	int res;
	if (port->cap_phy == 0) {
		tb_port_WARN(port, "does not have a PHY\n");
		return -EINVAL;
	}
	res = tb_port_read(port, &phy, TB_CFG_PORT, port->cap_phy, 2);
	if (res)
		return res;
	return phy.state;
}

/**
 * tb_wait_for_port() - wait for a port to become ready
 *
 * Wait up to 1 second for a port to reach state TB_PORT_UP. If
 * wait_if_unplugged is set then we also wait if the port is in state
 * TB_PORT_UNPLUGGED (it takes a while for the device to be registered after
 * switch resume). Otherwise we only wait if a device is registered but the link
 * has not yet been established.
 *
 * Return: Returns an error code on failure. Returns 0 if the port is not
 * connected or failed to reach state TB_PORT_UP within one second. Returns 1
 * if the port is connected and in state TB_PORT_UP.
 */
int tb_wait_for_port(struct tb_port *port, bool wait_if_unplugged)
{
	int retries = 10;
	int state;
	if (!port->cap_phy) {
		tb_port_WARN(port, "does not have PHY\n");
		return -EINVAL;
	}
	if (tb_is_upstream_port(port)) {
		tb_port_WARN(port, "is the upstream port\n");
		return -EINVAL;
	}

	while (retries--) {
		state = tb_port_state(port);
		if (state < 0)
			return state;
		if (state == TB_PORT_DISABLED) {
			tb_port_info(port, "is disabled (state: 0)\n");
			return 0;
		}
		if (state == TB_PORT_UNPLUGGED) {
			if (wait_if_unplugged) {
				/* used during resume */
				tb_port_info(port,
					     "is unplugged (state: 7), retrying...\n");
				msleep(100);
				continue;
			}
			tb_port_info(port, "is unplugged (state: 7)\n");
			return 0;
		}
		if (state == TB_PORT_UP) {
			tb_port_info(port,
				     "is connected, link is up (state: 2)\n");
			return 1;
		}

		/*
		 * After plug-in the state is TB_PORT_CONNECTING. Give it some
		 * time.
		 */
		tb_port_info(port,
			     "is connected, link is not up (state: %d), retrying...\n",
			     state);
		msleep(100);
	}
	tb_port_warn(port,
		     "failed to reach state TB_PORT_UP. Ignoring port...\n");
	return 0;
}

/**
 * tb_port_add_nfc_credits() - add/remove non flow controlled credits to port
 *
 * Change the number of NFC credits allocated to @port by @credits. To remove
 * NFC credits pass a negative amount of credits.
 *
 * Return: Returns 0 on success or an error code on failure.
 */
int tb_port_add_nfc_credits(struct tb_port *port, int credits)
{
	if (credits == 0)
		return 0;
	tb_port_info(port,
		     "adding %#x NFC credits (%#x -> %#x)",
		     credits,
		     port->config.nfc_credits,
		     port->config.nfc_credits + credits);
	port->config.nfc_credits += credits;
	return tb_port_write(port, &port->config.nfc_credits,
			     TB_CFG_PORT, 4, 1);
}

/**
 * tb_port_clear_counter() - clear a counter in TB_CFG_COUNTER
 *
 * Return: Returns 0 on success or an error code on failure.
 */
int tb_port_clear_counter(struct tb_port *port, int counter)
{
	u32 zero[3] = { 0, 0, 0 };
	tb_port_info(port, "clearing counter %d\n", counter);
	return tb_port_write(port, zero, TB_CFG_COUNTERS, 3 * counter, 3);
}

/**
 * tb_init_port() - initialize a port
 *
 * This is a helper method for tb_switch_alloc. Does not check or initialize
 * any downstream switches.
 *
 * Return: Returns 0 on success or an error code on failure.
 */
static int tb_init_port(struct tb_port *port)
{
	int res;
	int cap;

	res = tb_port_read(port, &port->config, TB_CFG_PORT, 0, 8);
	if (res)
		return res;

	/* Port 0 is the switch itself and has no PHY. */
	if (port->config.type == TB_TYPE_PORT && port->port != 0) {
		cap = tb_port_find_cap(port, TB_PORT_CAP_PHY);

		if (cap > 0)
			port->cap_phy = cap;
		else
			tb_port_WARN(port, "non switch port without a PHY\n");
	}

	tb_dump_port(port->sw->tb, &port->config);

	/* TODO: Read dual link port, DP port and more from EEPROM. */
	return 0;

}

/* switch utility functions */

static void tb_dump_switch(struct tb *tb, struct tb_regs_switch_header *sw)
{
	tb_info(tb,
		" Switch: %x:%x (Revision: %d, TB Version: %d)\n",
		sw->vendor_id, sw->device_id, sw->revision,
		sw->thunderbolt_version);
	tb_info(tb, "  Max Port Number: %d\n", sw->max_port_number);
	tb_info(tb, "  Config:\n");
	tb_info(tb,
		"   Upstream Port Number: %d Depth: %d Route String: %#llx Enabled: %d, PlugEventsDelay: %dms\n",
		sw->upstream_port_number, sw->depth,
		(((u64) sw->route_hi) << 32) | sw->route_lo,
		sw->enabled, sw->plug_events_delay);
	tb_info(tb,
		"   unknown1: %#x unknown4: %#x\n",
		sw->__unknown1, sw->__unknown4);
}

/**
 * reset_switch() - reconfigure route, enable and send TB_CFG_PKG_RESET
 *
 * Return: Returns 0 on success or an error code on failure.
 */
int tb_switch_reset(struct tb *tb, u64 route)
{
	struct tb_cfg_result res;
	struct tb_regs_switch_header header = {
		header.route_hi = route >> 32,
		header.route_lo = route,
		header.enabled = true,
	};
	tb_info(tb, "resetting switch at %llx\n", route);
	res.err = tb_cfg_write(tb->ctl, ((u32 *) &header) + 2, route,
			0, 2, 2, 2);
	if (res.err)
		return res.err;
	res = tb_cfg_reset(tb->ctl, route, TB_CFG_DEFAULT_TIMEOUT);
	if (res.err > 0)
		return -EIO;
	return res.err;
}

struct tb_switch *get_switch_at_route(struct tb_switch *sw, u64 route)
{
	u8 next_port = route; /*
			       * Routes use a stride of 8 bits,
			       * eventhough a port index has 6 bits at most.
			       * */
	if (route == 0)
		return sw;
	if (next_port > sw->config.max_port_number)
		return NULL;
	if (tb_is_upstream_port(&sw->ports[next_port]))
		return NULL;
	if (!sw->ports[next_port].remote)
		return NULL;
	return get_switch_at_route(sw->ports[next_port].remote->sw,
				   route >> TB_ROUTE_SHIFT);
}

/**
 * tb_plug_events_active() - enable/disable plug events on a switch
 *
 * Also configures a sane plug_events_delay of 255ms.
 *
 * Return: Returns 0 on success or an error code on failure.
 */
static int tb_plug_events_active(struct tb_switch *sw, bool active)
{
	u32 data;
	int res;

	if (!sw->config.enabled)
		return 0;

	sw->config.plug_events_delay = 0xff;
	res = tb_sw_write(sw, ((u32 *) &sw->config) + 4, TB_CFG_SWITCH, 4, 1);
	if (res)
		return res;

	res = tb_sw_read(sw, &data, TB_CFG_SWITCH, sw->cap_plug_events + 1, 1);
	if (res)
		return res;

	if (active) {
		data = data & 0xFFFFFF83;
		switch (sw->config.device_id) {
		case PCI_DEVICE_ID_INTEL_LIGHT_RIDGE:
		case PCI_DEVICE_ID_INTEL_EAGLE_RIDGE:
		case PCI_DEVICE_ID_INTEL_PORT_RIDGE:
			break;
		default:
			data |= 4;
		}
	} else {
		data = data | 0x7c;
	}
	return tb_sw_write(sw, &data, TB_CFG_SWITCH,
			   sw->cap_plug_events + 1, 1);
}

static ssize_t authorized_show(struct device *dev,
			       struct device_attribute *attr,
			       char *buf)
{
	struct tb_switch *sw = tb_to_switch(dev);

	return sprintf(buf, "%u\n", sw->authorized);
}

static int tb_switch_set_authorized(struct tb_switch *sw, unsigned int val)
{
	int ret = -EINVAL;

	if (mutex_lock_interruptible(&switch_lock))
		return -ERESTARTSYS;

	if (sw->authorized)
		goto unlock;

	switch (val) {
	/* Approve switch */
	case 1:
		if (sw->key)
			ret = tb_domain_approve_switch_key(sw->tb, sw);
		else
			ret = tb_domain_approve_switch(sw->tb, sw);
		break;

	/* Challenge switch */
	case 2:
		if (sw->key)
			ret = tb_domain_challenge_switch_key(sw->tb, sw);
		break;

	default:
		break;
	}

	if (!ret) {
		sw->authorized = val;
		/* Notify status change to the userspace */
		kobject_uevent(&sw->dev.kobj, KOBJ_CHANGE);
	}

unlock:
	mutex_unlock(&switch_lock);
	return ret;
}

static ssize_t authorized_store(struct device *dev,
				struct device_attribute *attr,
				const char *buf, size_t count)
{
	struct tb_switch *sw = tb_to_switch(dev);
	unsigned int val;
	ssize_t ret;

	ret = kstrtouint(buf, 0, &val);
	if (ret)
		return ret;
	if (val > 2)
		return -EINVAL;

	ret = tb_switch_set_authorized(sw, val);

	return ret ? ret : count;
}
static DEVICE_ATTR_RW(authorized);

static ssize_t device_show(struct device *dev, struct device_attribute *attr,
			   char *buf)
{
	struct tb_switch *sw = tb_to_switch(dev);

	return sprintf(buf, "%#x\n", sw->device);
}
static DEVICE_ATTR_RO(device);

static ssize_t
device_name_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct tb_switch *sw = tb_to_switch(dev);

	return sprintf(buf, "%s\n", sw->device_name ? sw->device_name : "");
}
static DEVICE_ATTR_RO(device_name);

static ssize_t key_show(struct device *dev, struct device_attribute *attr,
			char *buf)
{
	struct tb_switch *sw = tb_to_switch(dev);
	ssize_t ret;

	if (mutex_lock_interruptible(&switch_lock))
		return -ERESTARTSYS;

	if (sw->key)
		ret = sprintf(buf, "%*phN\n", TB_SWITCH_KEY_SIZE, sw->key);
	else
		ret = sprintf(buf, "\n");

	mutex_unlock(&switch_lock);
	return ret;
}

static ssize_t key_store(struct device *dev, struct device_attribute *attr,
			 const char *buf, size_t count)
{
	struct tb_switch *sw = tb_to_switch(dev);
	u8 key[TB_SWITCH_KEY_SIZE];
	ssize_t ret = count;

	if (count < 64)
		return -EINVAL;

	if (hex2bin(key, buf, sizeof(key)))
		return -EINVAL;

	if (mutex_lock_interruptible(&switch_lock))
		return -ERESTARTSYS;

	if (sw->authorized) {
		ret = -EBUSY;
	} else {
		kfree(sw->key);
		sw->key = kmemdup(key, sizeof(key), GFP_KERNEL);
		if (!sw->key)
			ret = -ENOMEM;
	}

	mutex_unlock(&switch_lock);
	return ret;
}
static DEVICE_ATTR_RW(key);

static ssize_t vendor_show(struct device *dev, struct device_attribute *attr,
			   char *buf)
{
	struct tb_switch *sw = tb_to_switch(dev);

	return sprintf(buf, "%#x\n", sw->vendor);
}
static DEVICE_ATTR_RO(vendor);

static ssize_t
vendor_name_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct tb_switch *sw = tb_to_switch(dev);

	return sprintf(buf, "%s\n", sw->vendor_name ? sw->vendor_name : "");
}
static DEVICE_ATTR_RO(vendor_name);

static ssize_t unique_id_show(struct device *dev, struct device_attribute *attr,
			      char *buf)
{
	struct tb_switch *sw = tb_to_switch(dev);

	return sprintf(buf, "%pUb\n", sw->uuid);
}
static DEVICE_ATTR_RO(unique_id);

static struct attribute *switch_attrs[] = {
	&dev_attr_authorized.attr,
	&dev_attr_device.attr,
	&dev_attr_device_name.attr,
	&dev_attr_key.attr,
	&dev_attr_vendor.attr,
	&dev_attr_vendor_name.attr,
	&dev_attr_unique_id.attr,
	NULL,
};

static umode_t switch_attr_is_visible(struct kobject *kobj,
				      struct attribute *attr, int n)
{
	struct device *dev = container_of(kobj, struct device, kobj);
	struct tb_switch *sw = tb_to_switch(dev);

	if (attr == &dev_attr_key.attr) {
		if (tb_route(sw) &&
		    sw->tb->security_level == TB_SECURITY_SECURE &&
		    sw->security_level == TB_SECURITY_SECURE)
			return attr->mode;
		return 0;
	}

	return attr->mode;
}

static struct attribute_group switch_group = {
	.is_visible = switch_attr_is_visible,
	.attrs = switch_attrs,
};

static const struct attribute_group *switch_groups[] = {
	&switch_group,
	NULL,
};

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);
	kfree(sw->ports);
	kfree(sw->drom);
	kfree(sw->key);
	kfree(sw);
}

struct device_type tb_switch_type = {
	.name = "thunderbolt_device",
	.release = tb_switch_release,
};

static int tb_switch_get_generation(struct tb_switch *sw)
{
	switch (sw->config.device_id) {
	case PCI_DEVICE_ID_INTEL_LIGHT_RIDGE:
	case PCI_DEVICE_ID_INTEL_EAGLE_RIDGE:
	case PCI_DEVICE_ID_INTEL_LIGHT_PEAK:
	case PCI_DEVICE_ID_INTEL_CACTUS_RIDGE_2C:
	case PCI_DEVICE_ID_INTEL_CACTUS_RIDGE_4C:
	case PCI_DEVICE_ID_INTEL_PORT_RIDGE:
	case PCI_DEVICE_ID_INTEL_REDWOOD_RIDGE_2C_BRIDGE:
	case PCI_DEVICE_ID_INTEL_REDWOOD_RIDGE_4C_BRIDGE:
		return 1;

	case PCI_DEVICE_ID_INTEL_WIN_RIDGE_2C_BRIDGE:
	case PCI_DEVICE_ID_INTEL_FALCON_RIDGE_2C_BRIDGE:
	case PCI_DEVICE_ID_INTEL_FALCON_RIDGE_4C_BRIDGE:
		return 2;

	case PCI_DEVICE_ID_INTEL_ALPINE_RIDGE_LP_BRIDGE:
	case PCI_DEVICE_ID_INTEL_ALPINE_RIDGE_2C_BRIDGE:
	case PCI_DEVICE_ID_INTEL_ALPINE_RIDGE_4C_BRIDGE:
	case PCI_DEVICE_ID_INTEL_ALPINE_RIDGE_C_2C_BRIDGE:
	case PCI_DEVICE_ID_INTEL_ALPINE_RIDGE_C_4C_BRIDGE:
		return 3;

	default:
		/*
		 * For unknown switches assume generation to be 1 to be
		 * on the safe side.
		 */
		tb_sw_warn(sw, "unsupported switch device id %#x\n",
			   sw->config.device_id);
		return 1;
	}
}

/**
 * tb_switch_alloc() - allocate a switch
 * @tb: Pointer to the owning domain
 * @parent: Parent device for this switch
 * @route: Route string for this switch
 *
 * Allocates and initializes a switch. Will not upload configuration to
 * the switch. For that you need to call tb_switch_configure()
 * separately. The returned switch should be released by calling
 * tb_switch_put().
 *
 * Return: Pointer to the allocated switch or %NULL in case of failure
 */
struct tb_switch *tb_switch_alloc(struct tb *tb, struct device *parent,
				  u64 route)
{
	int i;
	int cap;
	struct tb_switch *sw;
	int upstream_port = tb_cfg_get_upstream_port(tb->ctl, route);
	if (upstream_port < 0)
		return NULL;

	sw = kzalloc(sizeof(*sw), GFP_KERNEL);
	if (!sw)
		return NULL;

	sw->tb = tb;
	if (tb_cfg_read(tb->ctl, &sw->config, route, 0, TB_CFG_SWITCH, 0, 5))
		goto err_free_sw_ports;

	tb_info(tb, "current switch config:\n");
	tb_dump_switch(tb, &sw->config);

	/* configure switch */
	sw->config.upstream_port_number = upstream_port;
	sw->config.depth = tb_route_length(route);
	sw->config.route_lo = route;
	sw->config.route_hi = route >> 32;
	sw->config.enabled = 0;

	/* initialize ports */
	sw->ports = kcalloc(sw->config.max_port_number + 1, sizeof(*sw->ports),
				GFP_KERNEL);
	if (!sw->ports)
		goto err_free_sw_ports;

	for (i = 0; i <= sw->config.max_port_number; i++) {
		/* minimum setup for tb_find_cap and tb_drom_read to work */
		sw->ports[i].sw = sw;
		sw->ports[i].port = i;
	}

	sw->generation = tb_switch_get_generation(sw);

	cap = tb_switch_find_vse_cap(sw, TB_VSE_CAP_PLUG_EVENTS);
	if (cap < 0) {
		tb_sw_warn(sw, "cannot find TB_VSE_CAP_PLUG_EVENTS aborting\n");
		goto err_free_sw_ports;
	}
	sw->cap_plug_events = cap;

	/* Root switch is always authorized */
	if (!route)
		sw->authorized = true;

	device_initialize(&sw->dev);
	sw->dev.parent = parent;
	sw->dev.bus = &tb_bus_type;
	sw->dev.type = &tb_switch_type;
	sw->dev.groups = switch_groups;
	dev_set_name(&sw->dev, "%u-%llx", tb->index, tb_route(sw));

	return sw;

err_free_sw_ports:
	kfree(sw->ports);
	kfree(sw);

	return NULL;
}

/**
 * tb_switch_configure() - Uploads configuration to the switch
 * @sw: Switch to configure
 *
 * Call this function before the switch is added to the system. It will
 * upload configuration to the switch and makes it available for the
 * connection manager to use.
 *
 * Return: %0 in case of success and negative errno in case of failure
 */
int tb_switch_configure(struct tb_switch *sw)
{
	struct tb *tb = sw->tb;
	u64 route;
	int ret;

	route = tb_route(sw);
	tb_info(tb,
		"initializing Switch at %#llx (depth: %d, up port: %d)\n",
		route, tb_route_length(route), sw->config.upstream_port_number);

	if (sw->config.vendor_id != PCI_VENDOR_ID_INTEL)
		tb_sw_warn(sw, "unknown switch vendor id %#x\n",
			   sw->config.vendor_id);

	sw->config.enabled = 1;

	/* upload configuration */
	ret = tb_sw_write(sw, 1 + (u32 *)&sw->config, TB_CFG_SWITCH, 1, 3);
	if (ret)
		return ret;

	return tb_plug_events_active(sw, true);
}

static void tb_switch_set_uuid(struct tb_switch *sw)
{
	u32 uuid[4];
	int cap;

	if (sw->uuid)
		return;

	/*
	 * The newer controllers include fused UUID as part of link
	 * controller specific registers
	 */
	cap = tb_switch_find_vse_cap(sw, TB_VSE_CAP_LINK_CONTROLLER);
	if (cap > 0) {
		tb_sw_read(sw, uuid, TB_CFG_SWITCH, cap + 3, 4);
	} else {
		/*
		 * ICM generates UUID based on UID and fills the upper
		 * two words with ones. This is not strictly following
		 * UUID format but we want to be compatible with it so
		 * we do the same here.
		 */
		uuid[0] = sw->uid & 0xffffffff;
		uuid[1] = (sw->uid >> 32) & 0xffffffff;
		uuid[2] = 0xffffffff;
		uuid[3] = 0xffffffff;
	}

	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
 *
 * This is the last step in adding switch to the domain. It will read
 * identification information from DROM and initializes ports so that
 * they can be used to connect other switches. The switch will be
 * exposed to the userspace when this function successfully returns. To
 * remove and release the switch, call tb_switch_remove().
 *
 * Return: %0 in case of success and negative errno in case of failure
 */
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) {
		tb_sw_warn(sw, "tb_eeprom_read_rom failed\n");
		return ret;
	}
	tb_sw_info(sw, "uid: %#llx\n", sw->uid);

	tb_switch_set_uuid(sw);

	for (i = 0; i <= sw->config.max_port_number; i++) {
		if (sw->ports[i].disabled) {
			tb_port_info(&sw->ports[i], "disabled by eeprom\n");
			continue;
		}
		ret = tb_init_port(&sw->ports[i]);
		if (ret)
			return ret;
	}

	return device_add(&sw->dev);
}

/**
 * tb_switch_remove() - Remove and release a switch
 * @sw: Switch to remove
 *
 * This will remove the switch from the domain and release it after last
 * reference count drops to zero. If there are switches connected below
 * this switch, they will be removed as well.
 */
void tb_switch_remove(struct tb_switch *sw)
{
	int i;

	/* port 0 is the switch itself and never has a remote */
	for (i = 1; i <= sw->config.max_port_number; i++) {
		if (tb_is_upstream_port(&sw->ports[i]))
			continue;
		if (sw->ports[i].remote)
			tb_switch_remove(sw->ports[i].remote->sw);
		sw->ports[i].remote = NULL;
	}

	if (!sw->is_unplugged)
		tb_plug_events_active(sw, false);

	device_unregister(&sw->dev);
}

/**
 * tb_sw_set_unplugged() - set is_unplugged on switch and downstream switches
 */
void tb_sw_set_unplugged(struct tb_switch *sw)
{
	int i;
	if (sw == sw->tb->root_switch) {
		tb_sw_WARN(sw, "cannot unplug root switch\n");
		return;
	}
	if (sw->is_unplugged) {
		tb_sw_WARN(sw, "is_unplugged already set\n");
		return;
	}
	sw->is_unplugged = true;
	for (i = 0; i <= sw->config.max_port_number; i++) {
		if (!tb_is_upstream_port(&sw->ports[i]) && sw->ports[i].remote)
			tb_sw_set_unplugged(sw->ports[i].remote->sw);
	}
}

int tb_switch_resume(struct tb_switch *sw)
{
	int i, err;
	tb_sw_info(sw, "resuming switch\n");

	/*
	 * Check for UID of the connected switches except for root
	 * switch which we assume cannot be removed.
	 */
	if (tb_route(sw)) {
		u64 uid;

		err = tb_drom_read_uid_only(sw, &uid);
		if (err) {
			tb_sw_warn(sw, "uid read failed\n");
			return err;
		}
		if (sw->uid != uid) {
			tb_sw_info(sw,
				"changed while suspended (uid %#llx -> %#llx)\n",
				sw->uid, uid);
			return -ENODEV;
		}
	}

	/* upload configuration */
	err = tb_sw_write(sw, 1 + (u32 *) &sw->config, TB_CFG_SWITCH, 1, 3);
	if (err)
		return err;

	err = tb_plug_events_active(sw, true);
	if (err)
		return err;

	/* check for surviving downstream switches */
	for (i = 1; i <= sw->config.max_port_number; i++) {
		struct tb_port *port = &sw->ports[i];
		if (tb_is_upstream_port(port))
			continue;
		if (!port->remote)
			continue;
		if (tb_wait_for_port(port, true) <= 0
			|| tb_switch_resume(port->remote->sw)) {
			tb_port_warn(port,
				     "lost during suspend, disconnecting\n");
			tb_sw_set_unplugged(port->remote->sw);
		}
	}
	return 0;
}

void tb_switch_suspend(struct tb_switch *sw)
{
	int i, err;
	err = tb_plug_events_active(sw, false);
	if (err)
		return;

	for (i = 1; i <= sw->config.max_port_number; i++) {
		if (!tb_is_upstream_port(&sw->ports[i]) && sw->ports[i].remote)
			tb_switch_suspend(sw->ports[i].remote->sw);
	}
	/*
	 * TODO: invoke tb_cfg_prepare_to_sleep here? does not seem to have any
	 * effect?
	 */
}

struct tb_sw_lookup {
	struct tb *tb;
	u8 link;
	u8 depth;
	const uuid_be *uuid;
};

static int tb_switch_match(struct device *dev, void *data)
{
	struct tb_switch *sw = tb_to_switch(dev);
	struct tb_sw_lookup *lookup = data;

	if (!sw)
		return 0;
	if (sw->tb != lookup->tb)
		return 0;

	if (lookup->uuid)
		return !memcmp(sw->uuid, lookup->uuid, sizeof(*lookup->uuid));

	/* Root switch is matched only by depth */
	if (!lookup->depth)
		return !sw->depth;

	return sw->link == lookup->link && sw->depth == lookup->depth;
}

/**
 * tb_switch_find_by_link_depth() - Find switch by link and depth
 * @tb: Domain the switch belongs
 * @link: Link number the switch is connected
 * @depth: Depth of the switch in link
 *
 * Returned switch has reference count increased so the caller needs to
 * call tb_switch_put() when done with the switch.
 */
struct tb_switch *tb_switch_find_by_link_depth(struct tb *tb, u8 link, u8 depth)
{
	struct tb_sw_lookup lookup;
	struct device *dev;

	memset(&lookup, 0, sizeof(lookup));
	lookup.tb = tb;
	lookup.link = link;
	lookup.depth = depth;

	dev = bus_find_device(&tb_bus_type, NULL, &lookup, tb_switch_match);
	if (dev)
		return tb_to_switch(dev);

	return NULL;
}

/**
 * tb_switch_find_by_link_depth() - Find switch by UUID
 * @tb: Domain the switch belongs
 * @uuid: UUID to look for
 *
 * Returned switch has reference count increased so the caller needs to
 * call tb_switch_put() when done with the switch.
 */
struct tb_switch *tb_switch_find_by_uuid(struct tb *tb, const uuid_be *uuid)
{
	struct tb_sw_lookup lookup;
	struct device *dev;

	memset(&lookup, 0, sizeof(lookup));
	lookup.tb = tb;
	lookup.uuid = uuid;

	dev = bus_find_device(&tb_bus_type, NULL, &lookup, tb_switch_match);
	if (dev)
		return tb_to_switch(dev);

	return NULL;
}