// SPDX-License-Identifier: GPL-2.0
/*
 * Thunderbolt driver - Tunneling support
 *
 * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
 * Copyright (C) 2019, Intel Corporation
 */

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

#include "tunnel.h"
#include "tb.h"

/* PCIe adapters use always HopID of 8 for both directions */
#define TB_PCI_HOPID                    8

#define TB_PCI_PATH_DOWN                0
#define TB_PCI_PATH_UP                  1

/* USB3 adapters use always HopID of 8 for both directions */
#define TB_USB3_HOPID                   8

#define TB_USB3_PATH_DOWN               0
#define TB_USB3_PATH_UP                 1

/* DP adapters use HopID 8 for AUX and 9 for Video */
#define TB_DP_AUX_TX_HOPID              8
#define TB_DP_AUX_RX_HOPID              8
#define TB_DP_VIDEO_HOPID               9

#define TB_DP_VIDEO_PATH_OUT            0
#define TB_DP_AUX_PATH_OUT              1
#define TB_DP_AUX_PATH_IN               2

/* Minimum number of credits needed for PCIe path */
#define TB_MIN_PCIE_CREDITS             6U
/*
 * Number of credits we try to allocate for each DMA path if not limited
 * by the host router baMaxHI.
 */
#define TB_DMA_CREDITS                  14U
/* Minimum number of credits for DMA path */
#define TB_MIN_DMA_CREDITS              1U

static const char * const tb_tunnel_names[] = { "PCI", "DP", "DMA", "USB3" };

#define __TB_TUNNEL_PRINT(level, tunnel, fmt, arg...)                   \
        do {                                                            \
                struct tb_tunnel *__tunnel = (tunnel);                  \
                level(__tunnel->tb, "%llx:%x <-> %llx:%x (%s): " fmt,   \
                      tb_route(__tunnel->src_port->sw),                 \
                      __tunnel->src_port->port,                         \
                      tb_route(__tunnel->dst_port->sw),                 \
                      __tunnel->dst_port->port,                         \
                      tb_tunnel_names[__tunnel->type],                  \
                      ## arg);                                          \
        } while (0)

#define tb_tunnel_WARN(tunnel, fmt, arg...) \
        __TB_TUNNEL_PRINT(tb_WARN, tunnel, fmt, ##arg)
#define tb_tunnel_warn(tunnel, fmt, arg...) \
        __TB_TUNNEL_PRINT(tb_warn, tunnel, fmt, ##arg)
#define tb_tunnel_info(tunnel, fmt, arg...) \
        __TB_TUNNEL_PRINT(tb_info, tunnel, fmt, ##arg)
#define tb_tunnel_dbg(tunnel, fmt, arg...) \
        __TB_TUNNEL_PRINT(tb_dbg, tunnel, fmt, ##arg)

static inline unsigned int tb_usable_credits(const struct tb_port *port)
{
        return port->total_credits - port->ctl_credits;
}

/**
 * tb_available_credits() - Available credits for PCIe and DMA
 * @port: Lane adapter to check
 * @max_dp_streams: If non-%NULL stores maximum number of simultaneous DP
 *                  streams possible through this lane adapter
 */
static unsigned int tb_available_credits(const struct tb_port *port,
                                         size_t *max_dp_streams)
{
        const struct tb_switch *sw = port->sw;
        int credits, usb3, pcie, spare;
        size_t ndp;

        usb3 = tb_acpi_may_tunnel_usb3() ? sw->max_usb3_credits : 0;
        pcie = tb_acpi_may_tunnel_pcie() ? sw->max_pcie_credits : 0;

        if (tb_acpi_is_xdomain_allowed()) {
                spare = min_not_zero(sw->max_dma_credits, TB_DMA_CREDITS);
                /* Add some credits for potential second DMA tunnel */
                spare += TB_MIN_DMA_CREDITS;
        } else {
                spare = 0;
        }

        credits = tb_usable_credits(port);
        if (tb_acpi_may_tunnel_dp()) {
                /*
                 * Maximum number of DP streams possible through the
                 * lane adapter.
                 */
                ndp = (credits - (usb3 + pcie + spare)) /
                      (sw->min_dp_aux_credits + sw->min_dp_main_credits);
        } else {
                ndp = 0;
        }
        credits -= ndp * (sw->min_dp_aux_credits + sw->min_dp_main_credits);
        credits -= usb3;

        if (max_dp_streams)
                *max_dp_streams = ndp;

        return credits > 0 ? credits : 0;
}

static struct tb_tunnel *tb_tunnel_alloc(struct tb *tb, size_t npaths,
                                         enum tb_tunnel_type type)
{
        struct tb_tunnel *tunnel;

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

        tunnel->paths = kcalloc(npaths, sizeof(tunnel->paths[0]), GFP_KERNEL);
        if (!tunnel->paths) {
                tb_tunnel_free(tunnel);
                return NULL;
        }

        INIT_LIST_HEAD(&tunnel->list);
        tunnel->tb = tb;
        tunnel->npaths = npaths;
        tunnel->type = type;

        return tunnel;
}

static int tb_pci_activate(struct tb_tunnel *tunnel, bool activate)
{
        int res;

        res = tb_pci_port_enable(tunnel->src_port, activate);
        if (res)
                return res;

        if (tb_port_is_pcie_up(tunnel->dst_port))
                return tb_pci_port_enable(tunnel->dst_port, activate);

        return 0;
}

static int tb_pci_init_credits(struct tb_path_hop *hop)
{
        struct tb_port *port = hop->in_port;
        struct tb_switch *sw = port->sw;
        unsigned int credits;

        if (tb_port_use_credit_allocation(port)) {
                unsigned int available;

                available = tb_available_credits(port, NULL);
                credits = min(sw->max_pcie_credits, available);

                if (credits < TB_MIN_PCIE_CREDITS)
                        return -ENOSPC;

                credits = max(TB_MIN_PCIE_CREDITS, credits);
        } else {
                if (tb_port_is_null(port))
                        credits = port->bonded ? 32 : 16;
                else
                        credits = 7;
        }

        hop->initial_credits = credits;
        return 0;
}

static int tb_pci_init_path(struct tb_path *path)
{
        struct tb_path_hop *hop;

        path->egress_fc_enable = TB_PATH_SOURCE | TB_PATH_INTERNAL;
        path->egress_shared_buffer = TB_PATH_NONE;
        path->ingress_fc_enable = TB_PATH_ALL;
        path->ingress_shared_buffer = TB_PATH_NONE;
        path->priority = 3;
        path->weight = 1;
        path->drop_packages = 0;

        tb_path_for_each_hop(path, hop) {
                int ret;

                ret = tb_pci_init_credits(hop);
                if (ret)
                        return ret;
        }

        return 0;
}

/**
 * tb_tunnel_discover_pci() - Discover existing PCIe tunnels
 * @tb: Pointer to the domain structure
 * @down: PCIe downstream adapter
 *
 * If @down adapter is active, follows the tunnel to the PCIe upstream
 * adapter and back. Returns the discovered tunnel or %NULL if there was
 * no tunnel.
 */
struct tb_tunnel *tb_tunnel_discover_pci(struct tb *tb, struct tb_port *down)
{
        struct tb_tunnel *tunnel;
        struct tb_path *path;

        if (!tb_pci_port_is_enabled(down))
                return NULL;

        tunnel = tb_tunnel_alloc(tb, 2, TB_TUNNEL_PCI);
        if (!tunnel)
                return NULL;

        tunnel->activate = tb_pci_activate;
        tunnel->src_port = down;

        /*
         * Discover both paths even if they are not complete. We will
         * clean them up by calling tb_tunnel_deactivate() below in that
         * case.
         */
        path = tb_path_discover(down, TB_PCI_HOPID, NULL, -1,
                                &tunnel->dst_port, "PCIe Up");
        if (!path) {
                /* Just disable the downstream port */
                tb_pci_port_enable(down, false);
                goto err_free;
        }
        tunnel->paths[TB_PCI_PATH_UP] = path;
        if (tb_pci_init_path(tunnel->paths[TB_PCI_PATH_UP]))
                goto err_free;

        path = tb_path_discover(tunnel->dst_port, -1, down, TB_PCI_HOPID, NULL,
                                "PCIe Down");
        if (!path)
                goto err_deactivate;
        tunnel->paths[TB_PCI_PATH_DOWN] = path;
        if (tb_pci_init_path(tunnel->paths[TB_PCI_PATH_DOWN]))
                goto err_deactivate;

        /* Validate that the tunnel is complete */
        if (!tb_port_is_pcie_up(tunnel->dst_port)) {
                tb_port_warn(tunnel->dst_port,
                             "path does not end on a PCIe adapter, cleaning up\n");
                goto err_deactivate;
        }

        if (down != tunnel->src_port) {
                tb_tunnel_warn(tunnel, "path is not complete, cleaning up\n");
                goto err_deactivate;
        }

        if (!tb_pci_port_is_enabled(tunnel->dst_port)) {
                tb_tunnel_warn(tunnel,
                               "tunnel is not fully activated, cleaning up\n");
                goto err_deactivate;
        }

        tb_tunnel_dbg(tunnel, "discovered\n");
        return tunnel;

err_deactivate:
        tb_tunnel_deactivate(tunnel);
err_free:
        tb_tunnel_free(tunnel);

        return NULL;
}

/**
 * tb_tunnel_alloc_pci() - allocate a pci tunnel
 * @tb: Pointer to the domain structure
 * @up: PCIe upstream adapter port
 * @down: PCIe downstream adapter port
 *
 * Allocate a PCI tunnel. The ports must be of type TB_TYPE_PCIE_UP and
 * TB_TYPE_PCIE_DOWN.
 *
 * Return: Returns a tb_tunnel on success or NULL on failure.
 */
struct tb_tunnel *tb_tunnel_alloc_pci(struct tb *tb, struct tb_port *up,
                                      struct tb_port *down)
{
        struct tb_tunnel *tunnel;
        struct tb_path *path;

        tunnel = tb_tunnel_alloc(tb, 2, TB_TUNNEL_PCI);
        if (!tunnel)
                return NULL;

        tunnel->activate = tb_pci_activate;
        tunnel->src_port = down;
        tunnel->dst_port = up;

        path = tb_path_alloc(tb, down, TB_PCI_HOPID, up, TB_PCI_HOPID, 0,
                             "PCIe Down");
        if (!path)
                goto err_free;
        tunnel->paths[TB_PCI_PATH_DOWN] = path;
        if (tb_pci_init_path(path))
                goto err_free;

        path = tb_path_alloc(tb, up, TB_PCI_HOPID, down, TB_PCI_HOPID, 0,
                             "PCIe Up");
        if (!path)
                goto err_free;
        tunnel->paths[TB_PCI_PATH_UP] = path;
        if (tb_pci_init_path(path))
                goto err_free;

        return tunnel;

err_free:
        tb_tunnel_free(tunnel);
        return NULL;
}

static bool tb_dp_is_usb4(const struct tb_switch *sw)
{
        /* Titan Ridge DP adapters need the same treatment as USB4 */
        return tb_switch_is_usb4(sw) || tb_switch_is_titan_ridge(sw);
}

static int tb_dp_cm_handshake(struct tb_port *in, struct tb_port *out)
{
        int timeout = 10;
        u32 val;
        int ret;

        /* Both ends need to support this */
        if (!tb_dp_is_usb4(in->sw) || !tb_dp_is_usb4(out->sw))
                return 0;

        ret = tb_port_read(out, &val, TB_CFG_PORT,
                           out->cap_adap + DP_STATUS_CTRL, 1);
        if (ret)
                return ret;

        val |= DP_STATUS_CTRL_UF | DP_STATUS_CTRL_CMHS;

        ret = tb_port_write(out, &val, TB_CFG_PORT,
                            out->cap_adap + DP_STATUS_CTRL, 1);
        if (ret)
                return ret;

        do {
                ret = tb_port_read(out, &val, TB_CFG_PORT,
                                   out->cap_adap + DP_STATUS_CTRL, 1);
                if (ret)
                        return ret;
                if (!(val & DP_STATUS_CTRL_CMHS))
                        return 0;
                usleep_range(10, 100);
        } while (timeout--);

        return -ETIMEDOUT;
}

static inline u32 tb_dp_cap_get_rate(u32 val)
{
        u32 rate = (val & DP_COMMON_CAP_RATE_MASK) >> DP_COMMON_CAP_RATE_SHIFT;

        switch (rate) {
        case DP_COMMON_CAP_RATE_RBR:
                return 1620;
        case DP_COMMON_CAP_RATE_HBR:
                return 2700;
        case DP_COMMON_CAP_RATE_HBR2:
                return 5400;
        case DP_COMMON_CAP_RATE_HBR3:
                return 8100;
        default:
                return 0;
        }
}

static inline u32 tb_dp_cap_set_rate(u32 val, u32 rate)
{
        val &= ~DP_COMMON_CAP_RATE_MASK;
        switch (rate) {
        default:
                WARN(1, "invalid rate %u passed, defaulting to 1620 MB/s\n", rate);
                fallthrough;
        case 1620:
                val |= DP_COMMON_CAP_RATE_RBR << DP_COMMON_CAP_RATE_SHIFT;
                break;
        case 2700:
                val |= DP_COMMON_CAP_RATE_HBR << DP_COMMON_CAP_RATE_SHIFT;
                break;
        case 5400:
                val |= DP_COMMON_CAP_RATE_HBR2 << DP_COMMON_CAP_RATE_SHIFT;
                break;
        case 8100:
                val |= DP_COMMON_CAP_RATE_HBR3 << DP_COMMON_CAP_RATE_SHIFT;
                break;
        }
        return val;
}

static inline u32 tb_dp_cap_get_lanes(u32 val)
{
        u32 lanes = (val & DP_COMMON_CAP_LANES_MASK) >> DP_COMMON_CAP_LANES_SHIFT;

        switch (lanes) {
        case DP_COMMON_CAP_1_LANE:
                return 1;
        case DP_COMMON_CAP_2_LANES:
                return 2;
        case DP_COMMON_CAP_4_LANES:
                return 4;
        default:
                return 0;
        }
}

static inline u32 tb_dp_cap_set_lanes(u32 val, u32 lanes)
{
        val &= ~DP_COMMON_CAP_LANES_MASK;
        switch (lanes) {
        default:
                WARN(1, "invalid number of lanes %u passed, defaulting to 1\n",
                     lanes);
                fallthrough;
        case 1:
                val |= DP_COMMON_CAP_1_LANE << DP_COMMON_CAP_LANES_SHIFT;
                break;
        case 2:
                val |= DP_COMMON_CAP_2_LANES << DP_COMMON_CAP_LANES_SHIFT;
                break;
        case 4:
                val |= DP_COMMON_CAP_4_LANES << DP_COMMON_CAP_LANES_SHIFT;
                break;
        }
        return val;
}

static unsigned int tb_dp_bandwidth(unsigned int rate, unsigned int lanes)
{
        /* Tunneling removes the DP 8b/10b encoding */
        return rate * lanes * 8 / 10;
}

static int tb_dp_reduce_bandwidth(int max_bw, u32 in_rate, u32 in_lanes,
                                  u32 out_rate, u32 out_lanes, u32 *new_rate,
                                  u32 *new_lanes)
{
        static const u32 dp_bw[][2] = {
                /* Mb/s, lanes */
                { 8100, 4 }, /* 25920 Mb/s */
                { 5400, 4 }, /* 17280 Mb/s */
                { 8100, 2 }, /* 12960 Mb/s */
                { 2700, 4 }, /* 8640 Mb/s */
                { 5400, 2 }, /* 8640 Mb/s */
                { 8100, 1 }, /* 6480 Mb/s */
                { 1620, 4 }, /* 5184 Mb/s */
                { 5400, 1 }, /* 4320 Mb/s */
                { 2700, 2 }, /* 4320 Mb/s */
                { 1620, 2 }, /* 2592 Mb/s */
                { 2700, 1 }, /* 2160 Mb/s */
                { 1620, 1 }, /* 1296 Mb/s */
        };
        unsigned int i;

        /*
         * Find a combination that can fit into max_bw and does not
         * exceed the maximum rate and lanes supported by the DP OUT and
         * DP IN adapters.
         */
        for (i = 0; i < ARRAY_SIZE(dp_bw); i++) {
                if (dp_bw[i][0] > out_rate || dp_bw[i][1] > out_lanes)
                        continue;

                if (dp_bw[i][0] > in_rate || dp_bw[i][1] > in_lanes)
                        continue;

                if (tb_dp_bandwidth(dp_bw[i][0], dp_bw[i][1]) <= max_bw) {
                        *new_rate = dp_bw[i][0];
                        *new_lanes = dp_bw[i][1];
                        return 0;
                }
        }

        return -ENOSR;
}

static int tb_dp_xchg_caps(struct tb_tunnel *tunnel)
{
        u32 out_dp_cap, out_rate, out_lanes, in_dp_cap, in_rate, in_lanes, bw;
        struct tb_port *out = tunnel->dst_port;
        struct tb_port *in = tunnel->src_port;
        int ret, max_bw;

        /*
         * Copy DP_LOCAL_CAP register to DP_REMOTE_CAP register for
         * newer generation hardware.
         */
        if (in->sw->generation < 2 || out->sw->generation < 2)
                return 0;

        /*
         * Perform connection manager handshake between IN and OUT ports
         * before capabilities exchange can take place.
         */
        ret = tb_dp_cm_handshake(in, out);
        if (ret)
                return ret;

        /* Read both DP_LOCAL_CAP registers */
        ret = tb_port_read(in, &in_dp_cap, TB_CFG_PORT,
                           in->cap_adap + DP_LOCAL_CAP, 1);
        if (ret)
                return ret;

        ret = tb_port_read(out, &out_dp_cap, TB_CFG_PORT,
                           out->cap_adap + DP_LOCAL_CAP, 1);
        if (ret)
                return ret;

        /* Write IN local caps to OUT remote caps */
        ret = tb_port_write(out, &in_dp_cap, TB_CFG_PORT,
                            out->cap_adap + DP_REMOTE_CAP, 1);
        if (ret)
                return ret;

        in_rate = tb_dp_cap_get_rate(in_dp_cap);
        in_lanes = tb_dp_cap_get_lanes(in_dp_cap);
        tb_port_dbg(in, "maximum supported bandwidth %u Mb/s x%u = %u Mb/s\n",
                    in_rate, in_lanes, tb_dp_bandwidth(in_rate, in_lanes));

        /*
         * If the tunnel bandwidth is limited (max_bw is set) then see
         * if we need to reduce bandwidth to fit there.
         */
        out_rate = tb_dp_cap_get_rate(out_dp_cap);
        out_lanes = tb_dp_cap_get_lanes(out_dp_cap);
        bw = tb_dp_bandwidth(out_rate, out_lanes);
        tb_port_dbg(out, "maximum supported bandwidth %u Mb/s x%u = %u Mb/s\n",
                    out_rate, out_lanes, bw);

        if (in->sw->config.depth < out->sw->config.depth)
                max_bw = tunnel->max_down;
        else
                max_bw = tunnel->max_up;

        if (max_bw && bw > max_bw) {
                u32 new_rate, new_lanes, new_bw;

                ret = tb_dp_reduce_bandwidth(max_bw, in_rate, in_lanes,
                                             out_rate, out_lanes, &new_rate,
                                             &new_lanes);
                if (ret) {
                        tb_port_info(out, "not enough bandwidth for DP tunnel\n");
                        return ret;
                }

                new_bw = tb_dp_bandwidth(new_rate, new_lanes);
                tb_port_dbg(out, "bandwidth reduced to %u Mb/s x%u = %u Mb/s\n",
                            new_rate, new_lanes, new_bw);

                /*
                 * Set new rate and number of lanes before writing it to
                 * the IN port remote caps.
                 */
                out_dp_cap = tb_dp_cap_set_rate(out_dp_cap, new_rate);
                out_dp_cap = tb_dp_cap_set_lanes(out_dp_cap, new_lanes);
        }

        return tb_port_write(in, &out_dp_cap, TB_CFG_PORT,
                             in->cap_adap + DP_REMOTE_CAP, 1);
}

static int tb_dp_activate(struct tb_tunnel *tunnel, bool active)
{
        int ret;

        if (active) {
                struct tb_path **paths;
                int last;

                paths = tunnel->paths;
                last = paths[TB_DP_VIDEO_PATH_OUT]->path_length - 1;

                tb_dp_port_set_hops(tunnel->src_port,
                        paths[TB_DP_VIDEO_PATH_OUT]->hops[0].in_hop_index,
                        paths[TB_DP_AUX_PATH_OUT]->hops[0].in_hop_index,
                        paths[TB_DP_AUX_PATH_IN]->hops[last].next_hop_index);

                tb_dp_port_set_hops(tunnel->dst_port,
                        paths[TB_DP_VIDEO_PATH_OUT]->hops[last].next_hop_index,
                        paths[TB_DP_AUX_PATH_IN]->hops[0].in_hop_index,
                        paths[TB_DP_AUX_PATH_OUT]->hops[last].next_hop_index);
        } else {
                tb_dp_port_hpd_clear(tunnel->src_port);
                tb_dp_port_set_hops(tunnel->src_port, 0, 0, 0);
                if (tb_port_is_dpout(tunnel->dst_port))
                        tb_dp_port_set_hops(tunnel->dst_port, 0, 0, 0);
        }

        ret = tb_dp_port_enable(tunnel->src_port, active);
        if (ret)
                return ret;

        if (tb_port_is_dpout(tunnel->dst_port))
                return tb_dp_port_enable(tunnel->dst_port, active);

        return 0;
}

static int tb_dp_consumed_bandwidth(struct tb_tunnel *tunnel, int *consumed_up,
                                    int *consumed_down)
{
        struct tb_port *in = tunnel->src_port;
        const struct tb_switch *sw = in->sw;
        u32 val, rate = 0, lanes = 0;
        int ret;

        if (tb_dp_is_usb4(sw)) {
                int timeout = 20;

                /*
                 * Wait for DPRX done. Normally it should be already set
                 * for active tunnel.
                 */
                do {
                        ret = tb_port_read(in, &val, TB_CFG_PORT,
                                           in->cap_adap + DP_COMMON_CAP, 1);
                        if (ret)
                                return ret;

                        if (val & DP_COMMON_CAP_DPRX_DONE) {
                                rate = tb_dp_cap_get_rate(val);
                                lanes = tb_dp_cap_get_lanes(val);
                                break;
                        }
                        msleep(250);
                } while (timeout--);

                if (!timeout)
                        return -ETIMEDOUT;
        } else if (sw->generation >= 2) {
                /*
                 * Read from the copied remote cap so that we take into
                 * account if capabilities were reduced during exchange.
                 */
                ret = tb_port_read(in, &val, TB_CFG_PORT,
                                   in->cap_adap + DP_REMOTE_CAP, 1);
                if (ret)
                        return ret;

                rate = tb_dp_cap_get_rate(val);
                lanes = tb_dp_cap_get_lanes(val);
        } else {
                /* No bandwidth management for legacy devices  */
                *consumed_up = 0;
                *consumed_down = 0;
                return 0;
        }

        if (in->sw->config.depth < tunnel->dst_port->sw->config.depth) {
                *consumed_up = 0;
                *consumed_down = tb_dp_bandwidth(rate, lanes);
        } else {
                *consumed_up = tb_dp_bandwidth(rate, lanes);
                *consumed_down = 0;
        }

        return 0;
}

static void tb_dp_init_aux_credits(struct tb_path_hop *hop)
{
        struct tb_port *port = hop->in_port;
        struct tb_switch *sw = port->sw;

        if (tb_port_use_credit_allocation(port))
                hop->initial_credits = sw->min_dp_aux_credits;
        else
                hop->initial_credits = 1;
}

static void tb_dp_init_aux_path(struct tb_path *path)
{
        struct tb_path_hop *hop;

        path->egress_fc_enable = TB_PATH_SOURCE | TB_PATH_INTERNAL;
        path->egress_shared_buffer = TB_PATH_NONE;
        path->ingress_fc_enable = TB_PATH_ALL;
        path->ingress_shared_buffer = TB_PATH_NONE;
        path->priority = 2;
        path->weight = 1;

        tb_path_for_each_hop(path, hop)
                tb_dp_init_aux_credits(hop);
}

static int tb_dp_init_video_credits(struct tb_path_hop *hop)
{
        struct tb_port *port = hop->in_port;
        struct tb_switch *sw = port->sw;

        if (tb_port_use_credit_allocation(port)) {
                unsigned int nfc_credits;
                size_t max_dp_streams;

                tb_available_credits(port, &max_dp_streams);
                /*
                 * Read the number of currently allocated NFC credits
                 * from the lane adapter. Since we only use them for DP
                 * tunneling we can use that to figure out how many DP
                 * tunnels already go through the lane adapter.
                 */
                nfc_credits = port->config.nfc_credits &
                                ADP_CS_4_NFC_BUFFERS_MASK;
                if (nfc_credits / sw->min_dp_main_credits > max_dp_streams)
                        return -ENOSPC;

                hop->nfc_credits = sw->min_dp_main_credits;
        } else {
                hop->nfc_credits = min(port->total_credits - 2, 12U);
        }

        return 0;
}

static int tb_dp_init_video_path(struct tb_path *path)
{
        struct tb_path_hop *hop;

        path->egress_fc_enable = TB_PATH_NONE;
        path->egress_shared_buffer = TB_PATH_NONE;
        path->ingress_fc_enable = TB_PATH_NONE;
        path->ingress_shared_buffer = TB_PATH_NONE;
        path->priority = 1;
        path->weight = 1;

        tb_path_for_each_hop(path, hop) {
                int ret;

                ret = tb_dp_init_video_credits(hop);
                if (ret)
                        return ret;
        }

        return 0;
}

/**
 * tb_tunnel_discover_dp() - Discover existing Display Port tunnels
 * @tb: Pointer to the domain structure
 * @in: DP in adapter
 *
 * If @in adapter is active, follows the tunnel to the DP out adapter
 * and back. Returns the discovered tunnel or %NULL if there was no
 * tunnel.
 *
 * Return: DP tunnel or %NULL if no tunnel found.
 */
struct tb_tunnel *tb_tunnel_discover_dp(struct tb *tb, struct tb_port *in)
{
        struct tb_tunnel *tunnel;
        struct tb_port *port;
        struct tb_path *path;

        if (!tb_dp_port_is_enabled(in))
                return NULL;

        tunnel = tb_tunnel_alloc(tb, 3, TB_TUNNEL_DP);
        if (!tunnel)
                return NULL;

        tunnel->init = tb_dp_xchg_caps;
        tunnel->activate = tb_dp_activate;
        tunnel->consumed_bandwidth = tb_dp_consumed_bandwidth;
        tunnel->src_port = in;

        path = tb_path_discover(in, TB_DP_VIDEO_HOPID, NULL, -1,
                                &tunnel->dst_port, "Video");
        if (!path) {
                /* Just disable the DP IN port */
                tb_dp_port_enable(in, false);
                goto err_free;
        }
        tunnel->paths[TB_DP_VIDEO_PATH_OUT] = path;
        if (tb_dp_init_video_path(tunnel->paths[TB_DP_VIDEO_PATH_OUT]))
                goto err_free;

        path = tb_path_discover(in, TB_DP_AUX_TX_HOPID, NULL, -1, NULL, "AUX TX");
        if (!path)
                goto err_deactivate;
        tunnel->paths[TB_DP_AUX_PATH_OUT] = path;
        tb_dp_init_aux_path(tunnel->paths[TB_DP_AUX_PATH_OUT]);

        path = tb_path_discover(tunnel->dst_port, -1, in, TB_DP_AUX_RX_HOPID,
                                &port, "AUX RX");
        if (!path)
                goto err_deactivate;
        tunnel->paths[TB_DP_AUX_PATH_IN] = path;
        tb_dp_init_aux_path(tunnel->paths[TB_DP_AUX_PATH_IN]);

        /* Validate that the tunnel is complete */
        if (!tb_port_is_dpout(tunnel->dst_port)) {
                tb_port_warn(in, "path does not end on a DP adapter, cleaning up\n");
                goto err_deactivate;
        }

        if (!tb_dp_port_is_enabled(tunnel->dst_port))
                goto err_deactivate;

        if (!tb_dp_port_hpd_is_active(tunnel->dst_port))
                goto err_deactivate;

        if (port != tunnel->src_port) {
                tb_tunnel_warn(tunnel, "path is not complete, cleaning up\n");
                goto err_deactivate;
        }

        tb_tunnel_dbg(tunnel, "discovered\n");
        return tunnel;

err_deactivate:
        tb_tunnel_deactivate(tunnel);
err_free:
        tb_tunnel_free(tunnel);

        return NULL;
}

/**
 * tb_tunnel_alloc_dp() - allocate a Display Port tunnel
 * @tb: Pointer to the domain structure
 * @in: DP in adapter port
 * @out: DP out adapter port
 * @max_up: Maximum available upstream bandwidth for the DP tunnel (%0
 *          if not limited)
 * @max_down: Maximum available downstream bandwidth for the DP tunnel
 *            (%0 if not limited)
 *
 * Allocates a tunnel between @in and @out that is capable of tunneling
 * Display Port traffic.
 *
 * Return: Returns a tb_tunnel on success or NULL on failure.
 */
struct tb_tunnel *tb_tunnel_alloc_dp(struct tb *tb, struct tb_port *in,
                                     struct tb_port *out, int max_up,
                                     int max_down)
{
        struct tb_tunnel *tunnel;
        struct tb_path **paths;
        struct tb_path *path;

        if (WARN_ON(!in->cap_adap || !out->cap_adap))
                return NULL;

        tunnel = tb_tunnel_alloc(tb, 3, TB_TUNNEL_DP);
        if (!tunnel)
                return NULL;

        tunnel->init = tb_dp_xchg_caps;
        tunnel->activate = tb_dp_activate;
        tunnel->consumed_bandwidth = tb_dp_consumed_bandwidth;
        tunnel->src_port = in;
        tunnel->dst_port = out;
        tunnel->max_up = max_up;
        tunnel->max_down = max_down;

        paths = tunnel->paths;

        path = tb_path_alloc(tb, in, TB_DP_VIDEO_HOPID, out, TB_DP_VIDEO_HOPID,
                             1, "Video");
        if (!path)
                goto err_free;
        tb_dp_init_video_path(path);
        paths[TB_DP_VIDEO_PATH_OUT] = path;

        path = tb_path_alloc(tb, in, TB_DP_AUX_TX_HOPID, out,
                             TB_DP_AUX_TX_HOPID, 1, "AUX TX");
        if (!path)
                goto err_free;
        tb_dp_init_aux_path(path);
        paths[TB_DP_AUX_PATH_OUT] = path;

        path = tb_path_alloc(tb, out, TB_DP_AUX_RX_HOPID, in,
                             TB_DP_AUX_RX_HOPID, 1, "AUX RX");
        if (!path)
                goto err_free;
        tb_dp_init_aux_path(path);
        paths[TB_DP_AUX_PATH_IN] = path;

        return tunnel;

err_free:
        tb_tunnel_free(tunnel);
        return NULL;
}

static unsigned int tb_dma_available_credits(const struct tb_port *port)
{
        const struct tb_switch *sw = port->sw;
        int credits;

        credits = tb_available_credits(port, NULL);
        if (tb_acpi_may_tunnel_pcie())
                credits -= sw->max_pcie_credits;
        credits -= port->dma_credits;

        return credits > 0 ? credits : 0;
}

static int tb_dma_reserve_credits(struct tb_path_hop *hop, unsigned int credits)
{
        struct tb_port *port = hop->in_port;

        if (tb_port_use_credit_allocation(port)) {
                unsigned int available = tb_dma_available_credits(port);

                /*
                 * Need to have at least TB_MIN_DMA_CREDITS, otherwise
                 * DMA path cannot be established.
                 */
                if (available < TB_MIN_DMA_CREDITS)
                        return -ENOSPC;

                while (credits > available)
                        credits--;

                tb_port_dbg(port, "reserving %u credits for DMA path\n",
                            credits);

                port->dma_credits += credits;
        } else {
                if (tb_port_is_null(port))
                        credits = port->bonded ? 14 : 6;
                else
                        credits = min(port->total_credits, credits);
        }

        hop->initial_credits = credits;
        return 0;
}

/* Path from lane adapter to NHI */
static int tb_dma_init_rx_path(struct tb_path *path, unsigned int credits)
{
        struct tb_path_hop *hop;
        unsigned int i, tmp;

        path->egress_fc_enable = TB_PATH_SOURCE | TB_PATH_INTERNAL;
        path->ingress_fc_enable = TB_PATH_ALL;
        path->egress_shared_buffer = TB_PATH_NONE;
        path->ingress_shared_buffer = TB_PATH_NONE;
        path->priority = 5;
        path->weight = 1;
        path->clear_fc = true;

        /*
         * First lane adapter is the one connected to the remote host.
         * We don't tunnel other traffic over this link so can use all
         * the credits (except the ones reserved for control traffic).
         */
        hop = &path->hops[0];
        tmp = min(tb_usable_credits(hop->in_port), credits);
        hop->initial_credits = tmp;
        hop->in_port->dma_credits += tmp;

        for (i = 1; i < path->path_length; i++) {
                int ret;

                ret = tb_dma_reserve_credits(&path->hops[i], credits);
                if (ret)
                        return ret;
        }

        return 0;
}

/* Path from NHI to lane adapter */
static int tb_dma_init_tx_path(struct tb_path *path, unsigned int credits)
{
        struct tb_path_hop *hop;

        path->egress_fc_enable = TB_PATH_ALL;
        path->ingress_fc_enable = TB_PATH_ALL;
        path->egress_shared_buffer = TB_PATH_NONE;
        path->ingress_shared_buffer = TB_PATH_NONE;
        path->priority = 5;
        path->weight = 1;
        path->clear_fc = true;

        tb_path_for_each_hop(path, hop) {
                int ret;

                ret = tb_dma_reserve_credits(hop, credits);
                if (ret)
                        return ret;
        }

        return 0;
}

static void tb_dma_release_credits(struct tb_path_hop *hop)
{
        struct tb_port *port = hop->in_port;

        if (tb_port_use_credit_allocation(port)) {
                port->dma_credits -= hop->initial_credits;

                tb_port_dbg(port, "released %u DMA path credits\n",
                            hop->initial_credits);
        }
}

static void tb_dma_deinit_path(struct tb_path *path)
{
        struct tb_path_hop *hop;

        tb_path_for_each_hop(path, hop)
                tb_dma_release_credits(hop);
}

static void tb_dma_deinit(struct tb_tunnel *tunnel)
{
        int i;

        for (i = 0; i < tunnel->npaths; i++) {
                if (!tunnel->paths[i])
                        continue;
                tb_dma_deinit_path(tunnel->paths[i]);
        }
}

/**
 * tb_tunnel_alloc_dma() - allocate a DMA tunnel
 * @tb: Pointer to the domain structure
 * @nhi: Host controller port
 * @dst: Destination null port which the other domain is connected to
 * @transmit_path: HopID used for transmitting packets
 * @transmit_ring: NHI ring number used to send packets towards the
 *                 other domain. Set to %-1 if TX path is not needed.
 * @receive_path: HopID used for receiving packets
 * @receive_ring: NHI ring number used to receive packets from the
 *                other domain. Set to %-1 if RX path is not needed.
 *
 * Return: Returns a tb_tunnel on success or NULL on failure.
 */
struct tb_tunnel *tb_tunnel_alloc_dma(struct tb *tb, struct tb_port *nhi,
                                      struct tb_port *dst, int transmit_path,
                                      int transmit_ring, int receive_path,
                                      int receive_ring)
{
        struct tb_tunnel *tunnel;
        size_t npaths = 0, i = 0;
        struct tb_path *path;
        int credits;

        if (receive_ring > 0)
                npaths++;
        if (transmit_ring > 0)
                npaths++;

        if (WARN_ON(!npaths))
                return NULL;

        tunnel = tb_tunnel_alloc(tb, npaths, TB_TUNNEL_DMA);
        if (!tunnel)
                return NULL;

        tunnel->src_port = nhi;
        tunnel->dst_port = dst;
        tunnel->deinit = tb_dma_deinit;

        credits = min_not_zero(TB_DMA_CREDITS, nhi->sw->max_dma_credits);

        if (receive_ring > 0) {
                path = tb_path_alloc(tb, dst, receive_path, nhi, receive_ring, 0,
                                     "DMA RX");
                if (!path)
                        goto err_free;
                tunnel->paths[i++] = path;
                if (tb_dma_init_rx_path(path, credits)) {
                        tb_tunnel_dbg(tunnel, "not enough buffers for RX path\n");
                        goto err_free;
                }
        }

        if (transmit_ring > 0) {
                path = tb_path_alloc(tb, nhi, transmit_ring, dst, transmit_path, 0,
                                     "DMA TX");
                if (!path)
                        goto err_free;
                tunnel->paths[i++] = path;
                if (tb_dma_init_tx_path(path, credits)) {
                        tb_tunnel_dbg(tunnel, "not enough buffers for TX path\n");
                        goto err_free;
                }
        }

        return tunnel;

err_free:
        tb_tunnel_free(tunnel);
        return NULL;
}

/**
 * tb_tunnel_match_dma() - Match DMA tunnel
 * @tunnel: Tunnel to match
 * @transmit_path: HopID used for transmitting packets. Pass %-1 to ignore.
 * @transmit_ring: NHI ring number used to send packets towards the
 *                 other domain. Pass %-1 to ignore.
 * @receive_path: HopID used for receiving packets. Pass %-1 to ignore.
 * @receive_ring: NHI ring number used to receive packets from the
 *                other domain. Pass %-1 to ignore.
 *
 * This function can be used to match specific DMA tunnel, if there are
 * multiple DMA tunnels going through the same XDomain connection.
 * Returns true if there is match and false otherwise.
 */
bool tb_tunnel_match_dma(const struct tb_tunnel *tunnel, int transmit_path,
                         int transmit_ring, int receive_path, int receive_ring)
{
        const struct tb_path *tx_path = NULL, *rx_path = NULL;
        int i;

        if (!receive_ring || !transmit_ring)
                return false;

        for (i = 0; i < tunnel->npaths; i++) {
                const struct tb_path *path = tunnel->paths[i];

                if (!path)
                        continue;

                if (tb_port_is_nhi(path->hops[0].in_port))
                        tx_path = path;
                else if (tb_port_is_nhi(path->hops[path->path_length - 1].out_port))
                        rx_path = path;
        }

        if (transmit_ring > 0 || transmit_path > 0) {
                if (!tx_path)
                        return false;
                if (transmit_ring > 0 &&
                    (tx_path->hops[0].in_hop_index != transmit_ring))
                        return false;
                if (transmit_path > 0 &&
                    (tx_path->hops[tx_path->path_length - 1].next_hop_index != transmit_path))
                        return false;
        }

        if (receive_ring > 0 || receive_path > 0) {
                if (!rx_path)
                        return false;
                if (receive_path > 0 &&
                    (rx_path->hops[0].in_hop_index != receive_path))
                        return false;
                if (receive_ring > 0 &&
                    (rx_path->hops[rx_path->path_length - 1].next_hop_index != receive_ring))
                        return false;
        }

        return true;
}

static int tb_usb3_max_link_rate(struct tb_port *up, struct tb_port *down)
{
        int ret, up_max_rate, down_max_rate;

        ret = usb4_usb3_port_max_link_rate(up);
        if (ret < 0)
                return ret;
        up_max_rate = ret;

        ret = usb4_usb3_port_max_link_rate(down);
        if (ret < 0)
                return ret;
        down_max_rate = ret;

        return min(up_max_rate, down_max_rate);
}

static int tb_usb3_init(struct tb_tunnel *tunnel)
{
        tb_tunnel_dbg(tunnel, "allocating initial bandwidth %d/%d Mb/s\n",
                      tunnel->allocated_up, tunnel->allocated_down);

        return usb4_usb3_port_allocate_bandwidth(tunnel->src_port,
                                                 &tunnel->allocated_up,
                                                 &tunnel->allocated_down);
}

static int tb_usb3_activate(struct tb_tunnel *tunnel, bool activate)
{
        int res;

        res = tb_usb3_port_enable(tunnel->src_port, activate);
        if (res)
                return res;

        if (tb_port_is_usb3_up(tunnel->dst_port))
                return tb_usb3_port_enable(tunnel->dst_port, activate);

        return 0;
}

static int tb_usb3_consumed_bandwidth(struct tb_tunnel *tunnel,
                int *consumed_up, int *consumed_down)
{
        int pcie_enabled = tb_acpi_may_tunnel_pcie();

        /*
         * PCIe tunneling, if enabled, affects the USB3 bandwidth so
         * take that it into account here.
         */
        *consumed_up = tunnel->allocated_up * (3 + pcie_enabled) / 3;
        *consumed_down = tunnel->allocated_down * (3 + pcie_enabled) / 3;
        return 0;
}

static int tb_usb3_release_unused_bandwidth(struct tb_tunnel *tunnel)
{
        int ret;

        ret = usb4_usb3_port_release_bandwidth(tunnel->src_port,
                                               &tunnel->allocated_up,
                                               &tunnel->allocated_down);
        if (ret)
                return ret;

        tb_tunnel_dbg(tunnel, "decreased bandwidth allocation to %d/%d Mb/s\n",
                      tunnel->allocated_up, tunnel->allocated_down);
        return 0;
}

static void tb_usb3_reclaim_available_bandwidth(struct tb_tunnel *tunnel,
                                                int *available_up,
                                                int *available_down)
{
        int ret, max_rate, allocate_up, allocate_down;

        ret = usb4_usb3_port_actual_link_rate(tunnel->src_port);
        if (ret < 0) {
                tb_tunnel_warn(tunnel, "failed to read actual link rate\n");
                return;
        } else if (!ret) {
                /* Use maximum link rate if the link valid is not set */
                ret = usb4_usb3_port_max_link_rate(tunnel->src_port);
                if (ret < 0) {
                        tb_tunnel_warn(tunnel, "failed to read maximum link rate\n");
                        return;
                }
        }

        /*
         * 90% of the max rate can be allocated for isochronous
         * transfers.
         */
        max_rate = ret * 90 / 100;

        /* No need to reclaim if already at maximum */
        if (tunnel->allocated_up >= max_rate &&
            tunnel->allocated_down >= max_rate)
                return;

        /* Don't go lower than what is already allocated */
        allocate_up = min(max_rate, *available_up);
        if (allocate_up < tunnel->allocated_up)
                allocate_up = tunnel->allocated_up;

        allocate_down = min(max_rate, *available_down);
        if (allocate_down < tunnel->allocated_down)
                allocate_down = tunnel->allocated_down;

        /* If no changes no need to do more */
        if (allocate_up == tunnel->allocated_up &&
            allocate_down == tunnel->allocated_down)
                return;

        ret = usb4_usb3_port_allocate_bandwidth(tunnel->src_port, &allocate_up,
                                                &allocate_down);
        if (ret) {
                tb_tunnel_info(tunnel, "failed to allocate bandwidth\n");
                return;
        }

        tunnel->allocated_up = allocate_up;
        *available_up -= tunnel->allocated_up;

        tunnel->allocated_down = allocate_down;
        *available_down -= tunnel->allocated_down;

        tb_tunnel_dbg(tunnel, "increased bandwidth allocation to %d/%d Mb/s\n",
                      tunnel->allocated_up, tunnel->allocated_down);
}

static void tb_usb3_init_credits(struct tb_path_hop *hop)
{
        struct tb_port *port = hop->in_port;
        struct tb_switch *sw = port->sw;
        unsigned int credits;

        if (tb_port_use_credit_allocation(port)) {
                credits = sw->max_usb3_credits;
        } else {
                if (tb_port_is_null(port))
                        credits = port->bonded ? 32 : 16;
                else
                        credits = 7;
        }

        hop->initial_credits = credits;
}

static void tb_usb3_init_path(struct tb_path *path)
{
        struct tb_path_hop *hop;

        path->egress_fc_enable = TB_PATH_SOURCE | TB_PATH_INTERNAL;
        path->egress_shared_buffer = TB_PATH_NONE;
        path->ingress_fc_enable = TB_PATH_ALL;
        path->ingress_shared_buffer = TB_PATH_NONE;
        path->priority = 3;
        path->weight = 3;
        path->drop_packages = 0;

        tb_path_for_each_hop(path, hop)
                tb_usb3_init_credits(hop);
}

/**
 * tb_tunnel_discover_usb3() - Discover existing USB3 tunnels
 * @tb: Pointer to the domain structure
 * @down: USB3 downstream adapter
 *
 * If @down adapter is active, follows the tunnel to the USB3 upstream
 * adapter and back. Returns the discovered tunnel or %NULL if there was
 * no tunnel.
 */
struct tb_tunnel *tb_tunnel_discover_usb3(struct tb *tb, struct tb_port *down)
{
        struct tb_tunnel *tunnel;
        struct tb_path *path;

        if (!tb_usb3_port_is_enabled(down))
                return NULL;

        tunnel = tb_tunnel_alloc(tb, 2, TB_TUNNEL_USB3);
        if (!tunnel)
                return NULL;

        tunnel->activate = tb_usb3_activate;
        tunnel->src_port = down;

        /*
         * Discover both paths even if they are not complete. We will
         * clean them up by calling tb_tunnel_deactivate() below in that
         * case.
         */
        path = tb_path_discover(down, TB_USB3_HOPID, NULL, -1,
                                &tunnel->dst_port, "USB3 Down");
        if (!path) {
                /* Just disable the downstream port */
                tb_usb3_port_enable(down, false);
                goto err_free;
        }
        tunnel->paths[TB_USB3_PATH_DOWN] = path;
        tb_usb3_init_path(tunnel->paths[TB_USB3_PATH_DOWN]);

        path = tb_path_discover(tunnel->dst_port, -1, down, TB_USB3_HOPID, NULL,
                                "USB3 Up");
        if (!path)
                goto err_deactivate;
        tunnel->paths[TB_USB3_PATH_UP] = path;
        tb_usb3_init_path(tunnel->paths[TB_USB3_PATH_UP]);

        /* Validate that the tunnel is complete */
        if (!tb_port_is_usb3_up(tunnel->dst_port)) {
                tb_port_warn(tunnel->dst_port,
                             "path does not end on an USB3 adapter, cleaning up\n");
                goto err_deactivate;
        }

        if (down != tunnel->src_port) {
                tb_tunnel_warn(tunnel, "path is not complete, cleaning up\n");
                goto err_deactivate;
        }

        if (!tb_usb3_port_is_enabled(tunnel->dst_port)) {
                tb_tunnel_warn(tunnel,
                               "tunnel is not fully activated, cleaning up\n");
                goto err_deactivate;
        }

        if (!tb_route(down->sw)) {
                int ret;

                /*
                 * Read the initial bandwidth allocation for the first
                 * hop tunnel.
                 */
                ret = usb4_usb3_port_allocated_bandwidth(down,
                        &tunnel->allocated_up, &tunnel->allocated_down);
                if (ret)
                        goto err_deactivate;

                tb_tunnel_dbg(tunnel, "currently allocated bandwidth %d/%d Mb/s\n",
                              tunnel->allocated_up, tunnel->allocated_down);

                tunnel->init = tb_usb3_init;
                tunnel->consumed_bandwidth = tb_usb3_consumed_bandwidth;
                tunnel->release_unused_bandwidth =
                        tb_usb3_release_unused_bandwidth;
                tunnel->reclaim_available_bandwidth =
                        tb_usb3_reclaim_available_bandwidth;
        }

        tb_tunnel_dbg(tunnel, "discovered\n");
        return tunnel;

err_deactivate:
        tb_tunnel_deactivate(tunnel);
err_free:
        tb_tunnel_free(tunnel);

        return NULL;
}

/**
 * tb_tunnel_alloc_usb3() - allocate a USB3 tunnel
 * @tb: Pointer to the domain structure
 * @up: USB3 upstream adapter port
 * @down: USB3 downstream adapter port
 * @max_up: Maximum available upstream bandwidth for the USB3 tunnel (%0
 *          if not limited).
 * @max_down: Maximum available downstream bandwidth for the USB3 tunnel
 *            (%0 if not limited).
 *
 * Allocate an USB3 tunnel. The ports must be of type @TB_TYPE_USB3_UP and
 * @TB_TYPE_USB3_DOWN.
 *
 * Return: Returns a tb_tunnel on success or %NULL on failure.
 */
struct tb_tunnel *tb_tunnel_alloc_usb3(struct tb *tb, struct tb_port *up,
                                       struct tb_port *down, int max_up,
                                       int max_down)
{
        struct tb_tunnel *tunnel;
        struct tb_path *path;
        int max_rate = 0;

        /*
         * Check that we have enough bandwidth available for the new
         * USB3 tunnel.
         */
        if (max_up > 0 || max_down > 0) {
                max_rate = tb_usb3_max_link_rate(down, up);
                if (max_rate < 0)
                        return NULL;

                /* Only 90% can be allocated for USB3 isochronous transfers */
                max_rate = max_rate * 90 / 100;
                tb_port_dbg(up, "required bandwidth for USB3 tunnel %d Mb/s\n",
                            max_rate);

                if (max_rate > max_up || max_rate > max_down) {
                        tb_port_warn(up, "not enough bandwidth for USB3 tunnel\n");
                        return NULL;
                }
        }

        tunnel = tb_tunnel_alloc(tb, 2, TB_TUNNEL_USB3);
        if (!tunnel)
                return NULL;

        tunnel->activate = tb_usb3_activate;
        tunnel->src_port = down;
        tunnel->dst_port = up;
        tunnel->max_up = max_up;
        tunnel->max_down = max_down;

        path = tb_path_alloc(tb, down, TB_USB3_HOPID, up, TB_USB3_HOPID, 0,
                             "USB3 Down");
        if (!path) {
                tb_tunnel_free(tunnel);
                return NULL;
        }
        tb_usb3_init_path(path);
        tunnel->paths[TB_USB3_PATH_DOWN] = path;

        path = tb_path_alloc(tb, up, TB_USB3_HOPID, down, TB_USB3_HOPID, 0,
                             "USB3 Up");
        if (!path) {
                tb_tunnel_free(tunnel);
                return NULL;
        }
        tb_usb3_init_path(path);
        tunnel->paths[TB_USB3_PATH_UP] = path;

        if (!tb_route(down->sw)) {
                tunnel->allocated_up = max_rate;
                tunnel->allocated_down = max_rate;

                tunnel->init = tb_usb3_init;
                tunnel->consumed_bandwidth = tb_usb3_consumed_bandwidth;
                tunnel->release_unused_bandwidth =
                        tb_usb3_release_unused_bandwidth;
                tunnel->reclaim_available_bandwidth =
                        tb_usb3_reclaim_available_bandwidth;
        }

        return tunnel;
}

/**
 * tb_tunnel_free() - free a tunnel
 * @tunnel: Tunnel to be freed
 *
 * Frees a tunnel. The tunnel does not need to be deactivated.
 */
void tb_tunnel_free(struct tb_tunnel *tunnel)
{
        int i;

        if (!tunnel)
                return;

        if (tunnel->deinit)
                tunnel->deinit(tunnel);

        for (i = 0; i < tunnel->npaths; i++) {
                if (tunnel->paths[i])
                        tb_path_free(tunnel->paths[i]);
        }

        kfree(tunnel->paths);
        kfree(tunnel);
}

/**
 * tb_tunnel_is_invalid - check whether an activated path is still valid
 * @tunnel: Tunnel to check
 */
bool tb_tunnel_is_invalid(struct tb_tunnel *tunnel)
{
        int i;

        for (i = 0; i < tunnel->npaths; i++) {
                WARN_ON(!tunnel->paths[i]->activated);
                if (tb_path_is_invalid(tunnel->paths[i]))
                        return true;
        }

        return false;
}

/**
 * tb_tunnel_restart() - activate a tunnel after a hardware reset
 * @tunnel: Tunnel to restart
 *
 * Return: 0 on success and negative errno in case if failure
 */
int tb_tunnel_restart(struct tb_tunnel *tunnel)
{
        int res, i;

        tb_tunnel_dbg(tunnel, "activating\n");

        /*
         * Make sure all paths are properly disabled before enabling
         * them again.
         */
        for (i = 0; i < tunnel->npaths; i++) {
                if (tunnel->paths[i]->activated) {
                        tb_path_deactivate(tunnel->paths[i]);
                        tunnel->paths[i]->activated = false;
                }
        }

        if (tunnel->init) {
                res = tunnel->init(tunnel);
                if (res)
                        return res;
        }

        for (i = 0; i < tunnel->npaths; i++) {
                res = tb_path_activate(tunnel->paths[i]);
                if (res)
                        goto err;
        }

        if (tunnel->activate) {
                res = tunnel->activate(tunnel, true);
                if (res)
                        goto err;
        }

        return 0;

err:
        tb_tunnel_warn(tunnel, "activation failed\n");
        tb_tunnel_deactivate(tunnel);
        return res;
}

/**
 * tb_tunnel_activate() - activate a tunnel
 * @tunnel: Tunnel to activate
 *
 * Return: Returns 0 on success or an error code on failure.
 */
int tb_tunnel_activate(struct tb_tunnel *tunnel)
{
        int i;

        for (i = 0; i < tunnel->npaths; i++) {
                if (tunnel->paths[i]->activated) {
                        tb_tunnel_WARN(tunnel,
                                       "trying to activate an already activated tunnel\n");
                        return -EINVAL;
                }
        }

        return tb_tunnel_restart(tunnel);
}

/**
 * tb_tunnel_deactivate() - deactivate a tunnel
 * @tunnel: Tunnel to deactivate
 */
void tb_tunnel_deactivate(struct tb_tunnel *tunnel)
{
        int i;

        tb_tunnel_dbg(tunnel, "deactivating\n");

        if (tunnel->activate)
                tunnel->activate(tunnel, false);

        for (i = 0; i < tunnel->npaths; i++) {
                if (tunnel->paths[i] && tunnel->paths[i]->activated)
                        tb_path_deactivate(tunnel->paths[i]);
        }
}

/**
 * tb_tunnel_port_on_path() - Does the tunnel go through port
 * @tunnel: Tunnel to check
 * @port: Port to check
 *
 * Returns true if @tunnel goes through @port (direction does not matter),
 * false otherwise.
 */
bool tb_tunnel_port_on_path(const struct tb_tunnel *tunnel,
                            const struct tb_port *port)
{
        int i;

        for (i = 0; i < tunnel->npaths; i++) {
                if (!tunnel->paths[i])
                        continue;

                if (tb_path_port_on_path(tunnel->paths[i], port))
                        return true;
        }

        return false;
}

static bool tb_tunnel_is_active(const struct tb_tunnel *tunnel)
{
        int i;

        for (i = 0; i < tunnel->npaths; i++) {
                if (!tunnel->paths[i])
                        return false;
                if (!tunnel->paths[i]->activated)
                        return false;
        }

        return true;
}

/**
 * tb_tunnel_consumed_bandwidth() - Return bandwidth consumed by the tunnel
 * @tunnel: Tunnel to check
 * @consumed_up: Consumed bandwidth in Mb/s from @dst_port to @src_port.
 *               Can be %NULL.
 * @consumed_down: Consumed bandwidth in Mb/s from @src_port to @dst_port.
 *                 Can be %NULL.
 *
 * Stores the amount of isochronous bandwidth @tunnel consumes in
 * @consumed_up and @consumed_down. In case of success returns %0,
 * negative errno otherwise.
 */
int tb_tunnel_consumed_bandwidth(struct tb_tunnel *tunnel, int *consumed_up,
                                 int *consumed_down)
{
        int up_bw = 0, down_bw = 0;

        if (!tb_tunnel_is_active(tunnel))
                goto out;

        if (tunnel->consumed_bandwidth) {
                int ret;

                ret = tunnel->consumed_bandwidth(tunnel, &up_bw, &down_bw);
                if (ret)
                        return ret;

                tb_tunnel_dbg(tunnel, "consumed bandwidth %d/%d Mb/s\n", up_bw,
                              down_bw);
        }

out:
        if (consumed_up)
                *consumed_up = up_bw;
        if (consumed_down)
                *consumed_down = down_bw;

        return 0;
}

/**
 * tb_tunnel_release_unused_bandwidth() - Release unused bandwidth
 * @tunnel: Tunnel whose unused bandwidth to release
 *
 * If tunnel supports dynamic bandwidth management (USB3 tunnels at the
 * moment) this function makes it to release all the unused bandwidth.
 *
 * Returns %0 in case of success and negative errno otherwise.
 */
int tb_tunnel_release_unused_bandwidth(struct tb_tunnel *tunnel)
{
        if (!tb_tunnel_is_active(tunnel))
                return 0;

        if (tunnel->release_unused_bandwidth) {
                int ret;

                ret = tunnel->release_unused_bandwidth(tunnel);
                if (ret)
                        return ret;
        }

        return 0;
}

/**
 * tb_tunnel_reclaim_available_bandwidth() - Reclaim available bandwidth
 * @tunnel: Tunnel reclaiming available bandwidth
 * @available_up: Available upstream bandwidth (in Mb/s)
 * @available_down: Available downstream bandwidth (in Mb/s)
 *
 * Reclaims bandwidth from @available_up and @available_down and updates
 * the variables accordingly (e.g decreases both according to what was
 * reclaimed by the tunnel). If nothing was reclaimed the values are
 * kept as is.
 */
void tb_tunnel_reclaim_available_bandwidth(struct tb_tunnel *tunnel,
                                           int *available_up,
                                           int *available_down)
{
        if (!tb_tunnel_is_active(tunnel))
                return;

        if (tunnel->reclaim_available_bandwidth)
                tunnel->reclaim_available_bandwidth(tunnel, available_up,
                                                    available_down);
}