linux/drivers/thunderbolt/ctl.c

/*
 * Thunderbolt Cactus Ridge driver - control channel and configuration commands
 *
 * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
 */

#include <linux/crc32.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/pci.h>
#include <linux/dmapool.h>
#include <linux/workqueue.h>

#include "ctl.h"


#define TB_CTL_RX_PKG_COUNT	10
#define TB_CTL_RETRIES		4

/**
 * struct tb_cfg - thunderbolt control channel
 */
struct tb_ctl {
	struct tb_nhi *nhi;
	struct tb_ring *tx;
	struct tb_ring *rx;

	struct dma_pool *frame_pool;
	struct ctl_pkg *rx_packets[TB_CTL_RX_PKG_COUNT];
	struct mutex request_queue_lock;
	struct list_head request_queue;
	bool running;

	event_cb callback;
	void *callback_data;
};


#define tb_ctl_WARN(ctl, format, arg...) \
	dev_WARN(&(ctl)->nhi->pdev->dev, format, ## arg)

#define tb_ctl_err(ctl, format, arg...) \
	dev_err(&(ctl)->nhi->pdev->dev, format, ## arg)

#define tb_ctl_warn(ctl, format, arg...) \
	dev_warn(&(ctl)->nhi->pdev->dev, format, ## arg)

#define tb_ctl_info(ctl, format, arg...) \
	dev_info(&(ctl)->nhi->pdev->dev, format, ## arg)

#define tb_ctl_dbg(ctl, format, arg...) \
	dev_dbg(&(ctl)->nhi->pdev->dev, format, ## arg)

static DECLARE_WAIT_QUEUE_HEAD(tb_cfg_request_cancel_queue);
/* Serializes access to request kref_get/put */
static DEFINE_MUTEX(tb_cfg_request_lock);

/**
 * tb_cfg_request_alloc() - Allocates a new config request
 *
 * This is refcounted object so when you are done with this, call
 * tb_cfg_request_put() to it.
 */
struct tb_cfg_request *tb_cfg_request_alloc(void)
{
	struct tb_cfg_request *req;

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

	kref_init(&req->kref);

	return req;
}

/**
 * tb_cfg_request_get() - Increase refcount of a request
 * @req: Request whose refcount is increased
 */
void tb_cfg_request_get(struct tb_cfg_request *req)
{
	mutex_lock(&tb_cfg_request_lock);
	kref_get(&req->kref);
	mutex_unlock(&tb_cfg_request_lock);
}

static void tb_cfg_request_destroy(struct kref *kref)
{
	struct tb_cfg_request *req = container_of(kref, typeof(*req), kref);

	kfree(req);
}

/**
 * tb_cfg_request_put() - Decrease refcount and possibly release the request
 * @req: Request whose refcount is decreased
 *
 * Call this function when you are done with the request. When refcount
 * goes to %0 the object is released.
 */
void tb_cfg_request_put(struct tb_cfg_request *req)
{
	mutex_lock(&tb_cfg_request_lock);
	kref_put(&req->kref, tb_cfg_request_destroy);
	mutex_unlock(&tb_cfg_request_lock);
}

static int tb_cfg_request_enqueue(struct tb_ctl *ctl,
				  struct tb_cfg_request *req)
{
	WARN_ON(test_bit(TB_CFG_REQUEST_ACTIVE, &req->flags));
	WARN_ON(req->ctl);

	mutex_lock(&ctl->request_queue_lock);
	if (!ctl->running) {
		mutex_unlock(&ctl->request_queue_lock);
		return -ENOTCONN;
	}
	req->ctl = ctl;
	list_add_tail(&req->list, &ctl->request_queue);
	set_bit(TB_CFG_REQUEST_ACTIVE, &req->flags);
	mutex_unlock(&ctl->request_queue_lock);
	return 0;
}

static void tb_cfg_request_dequeue(struct tb_cfg_request *req)
{
	struct tb_ctl *ctl = req->ctl;

	mutex_lock(&ctl->request_queue_lock);
	list_del(&req->list);
	clear_bit(TB_CFG_REQUEST_ACTIVE, &req->flags);
	if (test_bit(TB_CFG_REQUEST_CANCELED, &req->flags))
		wake_up(&tb_cfg_request_cancel_queue);
	mutex_unlock(&ctl->request_queue_lock);
}

static bool tb_cfg_request_is_active(struct tb_cfg_request *req)
{
	return test_bit(TB_CFG_REQUEST_ACTIVE, &req->flags);
}

static struct tb_cfg_request *
tb_cfg_request_find(struct tb_ctl *ctl, struct ctl_pkg *pkg)
{
	struct tb_cfg_request *req;
	bool found = false;

	mutex_lock(&pkg->ctl->request_queue_lock);
	list_for_each_entry(req, &pkg->ctl->request_queue, list) {
		tb_cfg_request_get(req);
		if (req->match(req, pkg)) {
			found = true;
			break;
		}
		tb_cfg_request_put(req);
	}
	mutex_unlock(&pkg->ctl->request_queue_lock);

	return found ? req : NULL;
}

/* utility functions */


static int check_header(const struct ctl_pkg *pkg, u32 len,
			enum tb_cfg_pkg_type type, u64 route)
{
	struct tb_cfg_header *header = pkg->buffer;

	/* check frame, TODO: frame flags */
	if (WARN(len != pkg->frame.size,
			"wrong framesize (expected %#x, got %#x)\n",
			len, pkg->frame.size))
		return -EIO;
	if (WARN(type != pkg->frame.eof, "wrong eof (expected %#x, got %#x)\n",
			type, pkg->frame.eof))
		return -EIO;
	if (WARN(pkg->frame.sof, "wrong sof (expected 0x0, got %#x)\n",
			pkg->frame.sof))
		return -EIO;

	/* check header */
	if (WARN(header->unknown != 1 << 9,
			"header->unknown is %#x\n", header->unknown))
		return -EIO;
	if (WARN(route != tb_cfg_get_route(header),
			"wrong route (expected %llx, got %llx)",
			route, tb_cfg_get_route(header)))
		return -EIO;
	return 0;
}

static int check_config_address(struct tb_cfg_address addr,
				enum tb_cfg_space space, u32 offset,
				u32 length)
{
	if (WARN(addr.zero, "addr.zero is %#x\n", addr.zero))
		return -EIO;
	if (WARN(space != addr.space, "wrong space (expected %x, got %x\n)",
			space, addr.space))
		return -EIO;
	if (WARN(offset != addr.offset, "wrong offset (expected %x, got %x\n)",
			offset, addr.offset))
		return -EIO;
	if (WARN(length != addr.length, "wrong space (expected %x, got %x\n)",
			length, addr.length))
		return -EIO;
	/*
	 * We cannot check addr->port as it is set to the upstream port of the
	 * sender.
	 */
	return 0;
}

static struct tb_cfg_result decode_error(const struct ctl_pkg *response)
{
	struct cfg_error_pkg *pkg = response->buffer;
	struct tb_cfg_result res = { 0 };
	res.response_route = tb_cfg_get_route(&pkg->header);
	res.response_port = 0;
	res.err = check_header(response, sizeof(*pkg), TB_CFG_PKG_ERROR,
			       tb_cfg_get_route(&pkg->header));
	if (res.err)
		return res;

	WARN(pkg->zero1, "pkg->zero1 is %#x\n", pkg->zero1);
	WARN(pkg->zero2, "pkg->zero1 is %#x\n", pkg->zero1);
	WARN(pkg->zero3, "pkg->zero1 is %#x\n", pkg->zero1);
	res.err = 1;
	res.tb_error = pkg->error;
	res.response_port = pkg->port;
	return res;

}

static struct tb_cfg_result parse_header(const struct ctl_pkg *pkg, u32 len,
					 enum tb_cfg_pkg_type type, u64 route)
{
	struct tb_cfg_header *header = pkg->buffer;
	struct tb_cfg_result res = { 0 };

	if (pkg->frame.eof == TB_CFG_PKG_ERROR)
		return decode_error(pkg);

	res.response_port = 0; /* will be updated later for cfg_read/write */
	res.response_route = tb_cfg_get_route(header);
	res.err = check_header(pkg, len, type, route);
	return res;
}

static void tb_cfg_print_error(struct tb_ctl *ctl,
			       const struct tb_cfg_result *res)
{
	WARN_ON(res->err != 1);
	switch (res->tb_error) {
	case TB_CFG_ERROR_PORT_NOT_CONNECTED:
		/* Port is not connected. This can happen during surprise
		 * removal. Do not warn. */
		return;
	case TB_CFG_ERROR_INVALID_CONFIG_SPACE:
		/*
		 * Invalid cfg_space/offset/length combination in
		 * cfg_read/cfg_write.
		 */
		tb_ctl_WARN(ctl,
			"CFG_ERROR(%llx:%x): Invalid config space or offset\n",
			res->response_route, res->response_port);
		return;
	case TB_CFG_ERROR_NO_SUCH_PORT:
		/*
		 * - The route contains a non-existent port.
		 * - The route contains a non-PHY port (e.g. PCIe).
		 * - The port in cfg_read/cfg_write does not exist.
		 */
		tb_ctl_WARN(ctl, "CFG_ERROR(%llx:%x): Invalid port\n",
			res->response_route, res->response_port);
		return;
	case TB_CFG_ERROR_LOOP:
		tb_ctl_WARN(ctl, "CFG_ERROR(%llx:%x): Route contains a loop\n",
			res->response_route, res->response_port);
		return;
	default:
		/* 5,6,7,9 and 11 are also valid error codes */
		tb_ctl_WARN(ctl, "CFG_ERROR(%llx:%x): Unknown error\n",
			res->response_route, res->response_port);
		return;
	}
}

static __be32 tb_crc(const void *data, size_t len)
{
	return cpu_to_be32(~__crc32c_le(~0, data, len));
}

static void tb_ctl_pkg_free(struct ctl_pkg *pkg)
{
	if (pkg) {
		dma_pool_free(pkg->ctl->frame_pool,
			      pkg->buffer, pkg->frame.buffer_phy);
		kfree(pkg);
	}
}

static struct ctl_pkg *tb_ctl_pkg_alloc(struct tb_ctl *ctl)
{
	struct ctl_pkg *pkg = kzalloc(sizeof(*pkg), GFP_KERNEL);
	if (!pkg)
		return NULL;
	pkg->ctl = ctl;
	pkg->buffer = dma_pool_alloc(ctl->frame_pool, GFP_KERNEL,
				     &pkg->frame.buffer_phy);
	if (!pkg->buffer) {
		kfree(pkg);
		return NULL;
	}
	return pkg;
}


/* RX/TX handling */

static void tb_ctl_tx_callback(struct tb_ring *ring, struct ring_frame *frame,
			       bool canceled)
{
	struct ctl_pkg *pkg = container_of(frame, typeof(*pkg), frame);
	tb_ctl_pkg_free(pkg);
}

/**
 * tb_cfg_tx() - transmit a packet on the control channel
 *
 * len must be a multiple of four.
 *
 * Return: Returns 0 on success or an error code on failure.
 */
static int tb_ctl_tx(struct tb_ctl *ctl, const void *data, size_t len,
		     enum tb_cfg_pkg_type type)
{
	int res;
	struct ctl_pkg *pkg;
	if (len % 4 != 0) { /* required for le->be conversion */
		tb_ctl_WARN(ctl, "TX: invalid size: %zu\n", len);
		return -EINVAL;
	}
	if (len > TB_FRAME_SIZE - 4) { /* checksum is 4 bytes */
		tb_ctl_WARN(ctl, "TX: packet too large: %zu/%d\n",
			    len, TB_FRAME_SIZE - 4);
		return -EINVAL;
	}
	pkg = tb_ctl_pkg_alloc(ctl);
	if (!pkg)
		return -ENOMEM;
	pkg->frame.callback = tb_ctl_tx_callback;
	pkg->frame.size = len + 4;
	pkg->frame.sof = type;
	pkg->frame.eof = type;
	cpu_to_be32_array(pkg->buffer, data, len / 4);
	*(__be32 *) (pkg->buffer + len) = tb_crc(pkg->buffer, len);

	res = tb_ring_tx(ctl->tx, &pkg->frame);
	if (res) /* ring is stopped */
		tb_ctl_pkg_free(pkg);
	return res;
}

/**
 * tb_ctl_handle_event() - acknowledge a plug event, invoke ctl->callback
 */
static bool tb_ctl_handle_event(struct tb_ctl *ctl, enum tb_cfg_pkg_type type,
				struct ctl_pkg *pkg, size_t size)
{
	return ctl->callback(ctl->callback_data, type, pkg->buffer, size);
}

static void tb_ctl_rx_submit(struct ctl_pkg *pkg)
{
	tb_ring_rx(pkg->ctl->rx, &pkg->frame); /*
					     * We ignore failures during stop.
					     * All rx packets are referenced
					     * from ctl->rx_packets, so we do
					     * not loose them.
					     */
}

static int tb_async_error(const struct ctl_pkg *pkg)
{
	const struct cfg_error_pkg *error = (const struct cfg_error_pkg *)pkg;

	if (pkg->frame.eof != TB_CFG_PKG_ERROR)
		return false;

	switch (error->error) {
	case TB_CFG_ERROR_LINK_ERROR:
	case TB_CFG_ERROR_HEC_ERROR_DETECTED:
	case TB_CFG_ERROR_FLOW_CONTROL_ERROR:
		return true;

	default:
		return false;
	}
}

static void tb_ctl_rx_callback(struct tb_ring *ring, struct ring_frame *frame,
			       bool canceled)
{
	struct ctl_pkg *pkg = container_of(frame, typeof(*pkg), frame);
	struct tb_cfg_request *req;
	__be32 crc32;

	if (canceled)
		return; /*
			 * ring is stopped, packet is referenced from
			 * ctl->rx_packets.
			 */

	if (frame->size < 4 || frame->size % 4 != 0) {
		tb_ctl_err(pkg->ctl, "RX: invalid size %#x, dropping packet\n",
			   frame->size);
		goto rx;
	}

	frame->size -= 4; /* remove checksum */
	crc32 = tb_crc(pkg->buffer, frame->size);
	be32_to_cpu_array(pkg->buffer, pkg->buffer, frame->size / 4);

	switch (frame->eof) {
	case TB_CFG_PKG_READ:
	case TB_CFG_PKG_WRITE:
	case TB_CFG_PKG_ERROR:
	case TB_CFG_PKG_OVERRIDE:
	case TB_CFG_PKG_RESET:
		if (*(__be32 *)(pkg->buffer + frame->size) != crc32) {
			tb_ctl_err(pkg->ctl,
				   "RX: checksum mismatch, dropping packet\n");
			goto rx;
		}
		if (tb_async_error(pkg)) {
			tb_ctl_handle_event(pkg->ctl, frame->eof,
					    pkg, frame->size);
			goto rx;
		}
		break;

	case TB_CFG_PKG_EVENT:
	case TB_CFG_PKG_XDOMAIN_RESP:
	case TB_CFG_PKG_XDOMAIN_REQ:
		if (*(__be32 *)(pkg->buffer + frame->size) != crc32) {
			tb_ctl_err(pkg->ctl,
				   "RX: checksum mismatch, dropping packet\n");
			goto rx;
		}
		/* Fall through */
	case TB_CFG_PKG_ICM_EVENT:
		if (tb_ctl_handle_event(pkg->ctl, frame->eof, pkg, frame->size))
			goto rx;
		break;

	default:
		break;
	}

	/*
	 * The received packet will be processed only if there is an
	 * active request and that the packet is what is expected. This
	 * prevents packets such as replies coming after timeout has
	 * triggered from messing with the active requests.
	 */
	req = tb_cfg_request_find(pkg->ctl, pkg);
	if (req) {
		if (req->copy(req, pkg))
			schedule_work(&req->work);
		tb_cfg_request_put(req);
	}

rx:
	tb_ctl_rx_submit(pkg);
}

static void tb_cfg_request_work(struct work_struct *work)
{
	struct tb_cfg_request *req = container_of(work, typeof(*req), work);

	if (!test_bit(TB_CFG_REQUEST_CANCELED, &req->flags))
		req->callback(req->callback_data);

	tb_cfg_request_dequeue(req);
	tb_cfg_request_put(req);
}

/**
 * tb_cfg_request() - Start control request not waiting for it to complete
 * @ctl: Control channel to use
 * @req: Request to start
 * @callback: Callback called when the request is completed
 * @callback_data: Data to be passed to @callback
 *
 * This queues @req on the given control channel without waiting for it
 * to complete. When the request completes @callback is called.
 */
int tb_cfg_request(struct tb_ctl *ctl, struct tb_cfg_request *req,
		   void (*callback)(void *), void *callback_data)
{
	int ret;

	req->flags = 0;
	req->callback = callback;
	req->callback_data = callback_data;
	INIT_WORK(&req->work, tb_cfg_request_work);
	INIT_LIST_HEAD(&req->list);

	tb_cfg_request_get(req);
	ret = tb_cfg_request_enqueue(ctl, req);
	if (ret)
		goto err_put;

	ret = tb_ctl_tx(ctl, req->request, req->request_size,
			req->request_type);
	if (ret)
		goto err_dequeue;

	if (!req->response)
		schedule_work(&req->work);

	return 0;

err_dequeue:
	tb_cfg_request_dequeue(req);
err_put:
	tb_cfg_request_put(req);

	return ret;
}

/**
 * tb_cfg_request_cancel() - Cancel a control request
 * @req: Request to cancel
 * @err: Error to assign to the request
 *
 * This function can be used to cancel ongoing request. It will wait
 * until the request is not active anymore.
 */
void tb_cfg_request_cancel(struct tb_cfg_request *req, int err)
{
	set_bit(TB_CFG_REQUEST_CANCELED, &req->flags);
	schedule_work(&req->work);
	wait_event(tb_cfg_request_cancel_queue, !tb_cfg_request_is_active(req));
	req->result.err = err;
}

static void tb_cfg_request_complete(void *data)
{
	complete(data);
}

/**
 * tb_cfg_request_sync() - Start control request and wait until it completes
 * @ctl: Control channel to use
 * @req: Request to start
 * @timeout_msec: Timeout how long to wait @req to complete
 *
 * Starts a control request and waits until it completes. If timeout
 * triggers the request is canceled before function returns. Note the
 * caller needs to make sure only one message for given switch is active
 * at a time.
 */
struct tb_cfg_result tb_cfg_request_sync(struct tb_ctl *ctl,
					 struct tb_cfg_request *req,
					 int timeout_msec)
{
	unsigned long timeout = msecs_to_jiffies(timeout_msec);
	struct tb_cfg_result res = { 0 };
	DECLARE_COMPLETION_ONSTACK(done);
	int ret;

	ret = tb_cfg_request(ctl, req, tb_cfg_request_complete, &done);
	if (ret) {
		res.err = ret;
		return res;
	}

	if (!wait_for_completion_timeout(&done, timeout))
		tb_cfg_request_cancel(req, -ETIMEDOUT);

	flush_work(&req->work);

	return req->result;
}

/* public interface, alloc/start/stop/free */

/**
 * tb_ctl_alloc() - allocate a control channel
 *
 * cb will be invoked once for every hot plug event.
 *
 * Return: Returns a pointer on success or NULL on failure.
 */
struct tb_ctl *tb_ctl_alloc(struct tb_nhi *nhi, event_cb cb, void *cb_data)
{
	int i;
	struct tb_ctl *ctl = kzalloc(sizeof(*ctl), GFP_KERNEL);
	if (!ctl)
		return NULL;
	ctl->nhi = nhi;
	ctl->callback = cb;
	ctl->callback_data = cb_data;

	mutex_init(&ctl->request_queue_lock);
	INIT_LIST_HEAD(&ctl->request_queue);
	ctl->frame_pool = dma_pool_create("thunderbolt_ctl", &nhi->pdev->dev,
					 TB_FRAME_SIZE, 4, 0);
	if (!ctl->frame_pool)
		goto err;

	ctl->tx = tb_ring_alloc_tx(nhi, 0, 10, RING_FLAG_NO_SUSPEND);
	if (!ctl->tx)
		goto err;

	ctl->rx = tb_ring_alloc_rx(nhi, 0, 10, RING_FLAG_NO_SUSPEND, 0xffff,
				0xffff);
	if (!ctl->rx)
		goto err;

	for (i = 0; i < TB_CTL_RX_PKG_COUNT; i++) {
		ctl->rx_packets[i] = tb_ctl_pkg_alloc(ctl);
		if (!ctl->rx_packets[i])
			goto err;
		ctl->rx_packets[i]->frame.callback = tb_ctl_rx_callback;
	}

	tb_ctl_info(ctl, "control channel created\n");
	return ctl;
err:
	tb_ctl_free(ctl);
	return NULL;
}

/**
 * tb_ctl_free() - free a control channel
 *
 * Must be called after tb_ctl_stop.
 *
 * Must NOT be called from ctl->callback.
 */
void tb_ctl_free(struct tb_ctl *ctl)
{
	int i;

	if (!ctl)
		return;

	if (ctl->rx)
		tb_ring_free(ctl->rx);
	if (ctl->tx)
		tb_ring_free(ctl->tx);

	/* free RX packets */
	for (i = 0; i < TB_CTL_RX_PKG_COUNT; i++)
		tb_ctl_pkg_free(ctl->rx_packets[i]);


	if (ctl->frame_pool)
		dma_pool_destroy(ctl->frame_pool);
	kfree(ctl);
}

/**
 * tb_cfg_start() - start/resume the control channel
 */
void tb_ctl_start(struct tb_ctl *ctl)
{
	int i;
	tb_ctl_info(ctl, "control channel starting...\n");
	tb_ring_start(ctl->tx); /* is used to ack hotplug packets, start first */
	tb_ring_start(ctl->rx);
	for (i = 0; i < TB_CTL_RX_PKG_COUNT; i++)
		tb_ctl_rx_submit(ctl->rx_packets[i]);

	ctl->running = true;
}

/**
 * control() - pause the control channel
 *
 * All invocations of ctl->callback will have finished after this method
 * returns.
 *
 * Must NOT be called from ctl->callback.
 */
void tb_ctl_stop(struct tb_ctl *ctl)
{
	mutex_lock(&ctl->request_queue_lock);
	ctl->running = false;
	mutex_unlock(&ctl->request_queue_lock);

	tb_ring_stop(ctl->rx);
	tb_ring_stop(ctl->tx);

	if (!list_empty(&ctl->request_queue))
		tb_ctl_WARN(ctl, "dangling request in request_queue\n");
	INIT_LIST_HEAD(&ctl->request_queue);
	tb_ctl_info(ctl, "control channel stopped\n");
}

/* public interface, commands */

/**
 * tb_cfg_error() - send error packet
 *
 * Return: Returns 0 on success or an error code on failure.
 */
int tb_cfg_error(struct tb_ctl *ctl, u64 route, u32 port,
		 enum tb_cfg_error error)
{
	struct cfg_error_pkg pkg = {
		.header = tb_cfg_make_header(route),
		.port = port,
		.error = error,
	};
	tb_ctl_info(ctl, "resetting error on %llx:%x.\n", route, port);
	return tb_ctl_tx(ctl, &pkg, sizeof(pkg), TB_CFG_PKG_ERROR);
}

static bool tb_cfg_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;

	if (pkg->frame.eof == TB_CFG_PKG_READ ||
	    pkg->frame.eof == TB_CFG_PKG_WRITE) {
		const struct cfg_read_pkg *req_hdr = req->request;
		const struct cfg_read_pkg *res_hdr = pkg->buffer;

		if (req_hdr->addr.seq != res_hdr->addr.seq)
			return false;
	}

	return true;
}

static bool tb_cfg_copy(struct tb_cfg_request *req, const struct ctl_pkg *pkg)
{
	struct tb_cfg_result res;

	/* Now make sure it is in expected format */
	res = parse_header(pkg, req->response_size, req->response_type,
			   tb_cfg_get_route(req->request));
	if (!res.err)
		memcpy(req->response, pkg->buffer, req->response_size);

	req->result = res;

	/* Always complete when first response is received */
	return true;
}

/**
 * tb_cfg_reset() - send a reset packet and wait for a response
 *
 * If the switch at route is incorrectly configured then we will not receive a
 * reply (even though the switch will reset). The caller should check for
 * -ETIMEDOUT and attempt to reconfigure the switch.
 */
struct tb_cfg_result tb_cfg_reset(struct tb_ctl *ctl, u64 route,
				  int timeout_msec)
{
	struct cfg_reset_pkg request = { .header = tb_cfg_make_header(route) };
	struct tb_cfg_result res = { 0 };
	struct tb_cfg_header reply;
	struct tb_cfg_request *req;

	req = tb_cfg_request_alloc();
	if (!req) {
		res.err = -ENOMEM;
		return res;
	}

	req->match = tb_cfg_match;
	req->copy = tb_cfg_copy;
	req->request = &request;
	req->request_size = sizeof(request);
	req->request_type = TB_CFG_PKG_RESET;
	req->response = &reply;
	req->response_size = sizeof(reply);
	req->response_type = TB_CFG_PKG_RESET;

	res = tb_cfg_request_sync(ctl, req, timeout_msec);

	tb_cfg_request_put(req);

	return res;
}

/**
 * tb_cfg_read() - read from config space into buffer
 *
 * Offset and length are in dwords.
 */
struct tb_cfg_result tb_cfg_read_raw(struct tb_ctl *ctl, void *buffer,
		u64 route, u32 port, enum tb_cfg_space space,
		u32 offset, u32 length, int timeout_msec)
{
	struct tb_cfg_result res = { 0 };
	struct cfg_read_pkg request = {
		.header = tb_cfg_make_header(route),
		.addr = {
			.port = port,
			.space = space,
			.offset = offset,
			.length = length,
		},
	};
	struct cfg_write_pkg reply;
	int retries = 0;

	while (retries < TB_CTL_RETRIES) {
		struct tb_cfg_request *req;

		req = tb_cfg_request_alloc();
		if (!req) {
			res.err = -ENOMEM;
			return res;
		}

		request.addr.seq = retries++;

		req->match = tb_cfg_match;
		req->copy = tb_cfg_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 != -ETIMEDOUT)
			break;

		/* Wait a bit (arbitrary time) until we send a retry */
		usleep_range(10, 100);
	}

	if (res.err)
		return res;

	res.response_port = reply.addr.port;
	res.err = check_config_address(reply.addr, space, offset, length);
	if (!res.err)
		memcpy(buffer, &reply.data, 4 * length);
	return res;
}

/**
 * tb_cfg_write() - write from buffer into config space
 *
 * Offset and length are in dwords.
 */
struct tb_cfg_result tb_cfg_write_raw(struct tb_ctl *ctl, const void *buffer,
		u64 route, u32 port, enum tb_cfg_space space,
		u32 offset, u32 length, int timeout_msec)
{
	struct tb_cfg_result res = { 0 };
	struct cfg_write_pkg request = {
		.header = tb_cfg_make_header(route),
		.addr = {
			.port = port,
			.space = space,
			.offset = offset,
			.length = length,
		},
	};
	struct cfg_read_pkg reply;
	int retries = 0;

	memcpy(&request.data, buffer, length * 4);

	while (retries < TB_CTL_RETRIES) {
		struct tb_cfg_request *req;

		req = tb_cfg_request_alloc();
		if (!req) {
			res.err = -ENOMEM;
			return res;
		}

		request.addr.seq = retries++;

		req->match = tb_cfg_match;
		req->copy = tb_cfg_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);

		if (res.err != -ETIMEDOUT)
			break;

		/* Wait a bit (arbitrary time) until we send a retry */
		usleep_range(10, 100);
	}

	if (res.err)
		return res;

	res.response_port = reply.addr.port;
	res.err = check_config_address(reply.addr, space, offset, length);
	return res;
}

int tb_cfg_read(struct tb_ctl *ctl, void *buffer, u64 route, u32 port,
		enum tb_cfg_space space, u32 offset, u32 length)
{
	struct tb_cfg_result res = tb_cfg_read_raw(ctl, buffer, route, port,
			space, offset, length, TB_CFG_DEFAULT_TIMEOUT);
	switch (res.err) {
	case 0:
		/* Success */
		break;

	case 1:
		/* Thunderbolt error, tb_error holds the actual number */
		tb_cfg_print_error(ctl, &res);
		return -EIO;

	case -ETIMEDOUT:
		tb_ctl_warn(ctl, "timeout reading config space %u from %#x\n",
			    space, offset);
		break;

	default:
		WARN(1, "tb_cfg_read: %d\n", res.err);
		break;
	}
	return res.err;
}

int tb_cfg_write(struct tb_ctl *ctl, const void *buffer, u64 route, u32 port,
		 enum tb_cfg_space space, u32 offset, u32 length)
{
	struct tb_cfg_result res = tb_cfg_write_raw(ctl, buffer, route, port,
			space, offset, length, TB_CFG_DEFAULT_TIMEOUT);
	switch (res.err) {
	case 0:
		/* Success */
		break;

	case 1:
		/* Thunderbolt error, tb_error holds the actual number */
		tb_cfg_print_error(ctl, &res);
		return -EIO;

	case -ETIMEDOUT:
		tb_ctl_warn(ctl, "timeout writing config space %u to %#x\n",
			    space, offset);
		break;

	default:
		WARN(1, "tb_cfg_write: %d\n", res.err);
		break;
	}
	return res.err;
}

/**
 * tb_cfg_get_upstream_port() - get upstream port number of switch at route
 *
 * Reads the first dword from the switches TB_CFG_SWITCH config area and
 * returns the port number from which the reply originated.
 *
 * Return: Returns the upstream port number on success or an error code on
 * failure.
 */
int tb_cfg_get_upstream_port(struct tb_ctl *ctl, u64 route)
{
	u32 dummy;
	struct tb_cfg_result res = tb_cfg_read_raw(ctl, &dummy, route, 0,
						   TB_CFG_SWITCH, 0, 1,
						   TB_CFG_DEFAULT_TIMEOUT);
	if (res.err == 1)
		return -EIO;
	if (res.err)
		return res.err;
	return res.response_port;
}