// SPDX-License-Identifier: GPL-2.0

/* net/sched/sch_taprio.c        Time Aware Priority Scheduler
 *
 * Authors:     Vinicius Costa Gomes <vinicius.gomes@intel.com>
 *
 */

#include <linux/types.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/list.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
#include <net/sch_generic.h>

static LIST_HEAD(taprio_list);
static DEFINE_SPINLOCK(taprio_list_lock);

#define TAPRIO_ALL_GATES_OPEN -1

struct sched_entry {
        struct list_head list;

        /* The instant that this entry "closes" and the next one
         * should open, the qdisc will make some effort so that no
         * packet leaves after this time.
         */
        ktime_t close_time;
        atomic_t budget;
        int index;
        u32 gate_mask;
        u32 interval;
        u8 command;
};

struct sched_gate_list {
        struct rcu_head rcu;
        struct list_head entries;
        size_t num_entries;
        ktime_t cycle_close_time;
        s64 cycle_time;
        s64 cycle_time_extension;
        s64 base_time;
};

struct taprio_sched {
        struct Qdisc **qdiscs;
        struct Qdisc *root;
        int clockid;
        atomic64_t picos_per_byte; /* Using picoseconds because for 10Gbps+
                                    * speeds it's sub-nanoseconds per byte
                                    */

        /* Protects the update side of the RCU protected current_entry */
        spinlock_t current_entry_lock;
        struct sched_entry __rcu *current_entry;
        struct sched_gate_list __rcu *oper_sched;
        struct sched_gate_list __rcu *admin_sched;
        ktime_t (*get_time)(void);
        struct hrtimer advance_timer;
        struct list_head taprio_list;
};

static ktime_t sched_base_time(const struct sched_gate_list *sched)
{
        if (!sched)
                return KTIME_MAX;

        return ns_to_ktime(sched->base_time);
}

static void taprio_free_sched_cb(struct rcu_head *head)
{
        struct sched_gate_list *sched = container_of(head, struct sched_gate_list, rcu);
        struct sched_entry *entry, *n;

        if (!sched)
                return;

        list_for_each_entry_safe(entry, n, &sched->entries, list) {
                list_del(&entry->list);
                kfree(entry);
        }

        kfree(sched);
}

static void switch_schedules(struct taprio_sched *q,
                             struct sched_gate_list **admin,
                             struct sched_gate_list **oper)
{
        rcu_assign_pointer(q->oper_sched, *admin);
        rcu_assign_pointer(q->admin_sched, NULL);

        if (*oper)
                call_rcu(&(*oper)->rcu, taprio_free_sched_cb);

        *oper = *admin;
        *admin = NULL;
}

static ktime_t get_cycle_time(struct sched_gate_list *sched)
{
        struct sched_entry *entry;
        ktime_t cycle = 0;

        if (sched->cycle_time != 0)
                return sched->cycle_time;

        list_for_each_entry(entry, &sched->entries, list)
                cycle = ktime_add_ns(cycle, entry->interval);

        sched->cycle_time = cycle;

        return cycle;
}

static int taprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                          struct sk_buff **to_free)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct Qdisc *child;
        int queue;

        queue = skb_get_queue_mapping(skb);

        child = q->qdiscs[queue];
        if (unlikely(!child))
                return qdisc_drop(skb, sch, to_free);

        qdisc_qstats_backlog_inc(sch, skb);
        sch->q.qlen++;

        return qdisc_enqueue(skb, child, to_free);
}

static struct sk_buff *taprio_peek(struct Qdisc *sch)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        struct sched_entry *entry;
        struct sk_buff *skb;
        u32 gate_mask;
        int i;

        rcu_read_lock();
        entry = rcu_dereference(q->current_entry);
        gate_mask = entry ? entry->gate_mask : TAPRIO_ALL_GATES_OPEN;
        rcu_read_unlock();

        if (!gate_mask)
                return NULL;

        for (i = 0; i < dev->num_tx_queues; i++) {
                struct Qdisc *child = q->qdiscs[i];
                int prio;
                u8 tc;

                if (unlikely(!child))
                        continue;

                skb = child->ops->peek(child);
                if (!skb)
                        continue;

                prio = skb->priority;
                tc = netdev_get_prio_tc_map(dev, prio);

                if (!(gate_mask & BIT(tc)))
                        continue;

                return skb;
        }

        return NULL;
}

static inline int length_to_duration(struct taprio_sched *q, int len)
{
        return div_u64(len * atomic64_read(&q->picos_per_byte), 1000);
}

static void taprio_set_budget(struct taprio_sched *q, struct sched_entry *entry)
{
        atomic_set(&entry->budget,
                   div64_u64((u64)entry->interval * 1000,
                             atomic64_read(&q->picos_per_byte)));
}

static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        struct sk_buff *skb = NULL;
        struct sched_entry *entry;
        u32 gate_mask;
        int i;

        if (atomic64_read(&q->picos_per_byte) == -1) {
                WARN_ONCE(1, "taprio: dequeue() called with unknown picos per byte.");
                return NULL;
        }

        rcu_read_lock();
        entry = rcu_dereference(q->current_entry);
        /* if there's no entry, it means that the schedule didn't
         * start yet, so force all gates to be open, this is in
         * accordance to IEEE 802.1Qbv-2015 Section 8.6.9.4.5
         * "AdminGateSates"
         */
        gate_mask = entry ? entry->gate_mask : TAPRIO_ALL_GATES_OPEN;

        if (!gate_mask)
                goto done;

        for (i = 0; i < dev->num_tx_queues; i++) {
                struct Qdisc *child = q->qdiscs[i];
                ktime_t guard;
                int prio;
                int len;
                u8 tc;

                if (unlikely(!child))
                        continue;

                skb = child->ops->peek(child);
                if (!skb)
                        continue;

                prio = skb->priority;
                tc = netdev_get_prio_tc_map(dev, prio);

                if (!(gate_mask & BIT(tc)))
                        continue;

                len = qdisc_pkt_len(skb);
                guard = ktime_add_ns(q->get_time(),
                                     length_to_duration(q, len));

                /* In the case that there's no gate entry, there's no
                 * guard band ...
                 */
                if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
                    ktime_after(guard, entry->close_time))
                        continue;

                /* ... and no budget. */
                if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
                    atomic_sub_return(len, &entry->budget) < 0)
                        continue;

                skb = child->ops->dequeue(child);
                if (unlikely(!skb))
                        goto done;

                qdisc_bstats_update(sch, skb);
                qdisc_qstats_backlog_dec(sch, skb);
                sch->q.qlen--;

                goto done;
        }

done:
        rcu_read_unlock();

        return skb;
}

static bool should_restart_cycle(const struct sched_gate_list *oper,
                                 const struct sched_entry *entry)
{
        if (list_is_last(&entry->list, &oper->entries))
                return true;

        if (ktime_compare(entry->close_time, oper->cycle_close_time) == 0)
                return true;

        return false;
}

static bool should_change_schedules(const struct sched_gate_list *admin,
                                    const struct sched_gate_list *oper,
                                    ktime_t close_time)
{
        ktime_t next_base_time, extension_time;

        if (!admin)
                return false;

        next_base_time = sched_base_time(admin);

        /* This is the simple case, the close_time would fall after
         * the next schedule base_time.
         */
        if (ktime_compare(next_base_time, close_time) <= 0)
                return true;

        /* This is the cycle_time_extension case, if the close_time
         * plus the amount that can be extended would fall after the
         * next schedule base_time, we can extend the current schedule
         * for that amount.
         */
        extension_time = ktime_add_ns(close_time, oper->cycle_time_extension);

        /* FIXME: the IEEE 802.1Q-2018 Specification isn't clear about
         * how precisely the extension should be made. So after
         * conformance testing, this logic may change.
         */
        if (ktime_compare(next_base_time, extension_time) <= 0)
                return true;

        return false;
}

static enum hrtimer_restart advance_sched(struct hrtimer *timer)
{
        struct taprio_sched *q = container_of(timer, struct taprio_sched,
                                              advance_timer);
        struct sched_gate_list *oper, *admin;
        struct sched_entry *entry, *next;
        struct Qdisc *sch = q->root;
        ktime_t close_time;

        spin_lock(&q->current_entry_lock);
        entry = rcu_dereference_protected(q->current_entry,
                                          lockdep_is_held(&q->current_entry_lock));
        oper = rcu_dereference_protected(q->oper_sched,
                                         lockdep_is_held(&q->current_entry_lock));
        admin = rcu_dereference_protected(q->admin_sched,
                                          lockdep_is_held(&q->current_entry_lock));

        if (!oper)
                switch_schedules(q, &admin, &oper);

        /* This can happen in two cases: 1. this is the very first run
         * of this function (i.e. we weren't running any schedule
         * previously); 2. The previous schedule just ended. The first
         * entry of all schedules are pre-calculated during the
         * schedule initialization.
         */
        if (unlikely(!entry || entry->close_time == oper->base_time)) {
                next = list_first_entry(&oper->entries, struct sched_entry,
                                        list);
                close_time = next->close_time;
                goto first_run;
        }

        if (should_restart_cycle(oper, entry)) {
                next = list_first_entry(&oper->entries, struct sched_entry,
                                        list);
                oper->cycle_close_time = ktime_add_ns(oper->cycle_close_time,
                                                      oper->cycle_time);
        } else {
                next = list_next_entry(entry, list);
        }

        close_time = ktime_add_ns(entry->close_time, next->interval);
        close_time = min_t(ktime_t, close_time, oper->cycle_close_time);

        if (should_change_schedules(admin, oper, close_time)) {
                /* Set things so the next time this runs, the new
                 * schedule runs.
                 */
                close_time = sched_base_time(admin);
                switch_schedules(q, &admin, &oper);
        }

        next->close_time = close_time;
        taprio_set_budget(q, next);

first_run:
        rcu_assign_pointer(q->current_entry, next);
        spin_unlock(&q->current_entry_lock);

        hrtimer_set_expires(&q->advance_timer, close_time);

        rcu_read_lock();
        __netif_schedule(sch);
        rcu_read_unlock();

        return HRTIMER_RESTART;
}

static const struct nla_policy entry_policy[TCA_TAPRIO_SCHED_ENTRY_MAX + 1] = {
        [TCA_TAPRIO_SCHED_ENTRY_INDEX]     = { .type = NLA_U32 },
        [TCA_TAPRIO_SCHED_ENTRY_CMD]       = { .type = NLA_U8 },
        [TCA_TAPRIO_SCHED_ENTRY_GATE_MASK] = { .type = NLA_U32 },
        [TCA_TAPRIO_SCHED_ENTRY_INTERVAL]  = { .type = NLA_U32 },
};

static const struct nla_policy entry_list_policy[TCA_TAPRIO_SCHED_MAX + 1] = {
        [TCA_TAPRIO_SCHED_ENTRY] = { .type = NLA_NESTED },
};

static const struct nla_policy taprio_policy[TCA_TAPRIO_ATTR_MAX + 1] = {
        [TCA_TAPRIO_ATTR_PRIOMAP]              = {
                .len = sizeof(struct tc_mqprio_qopt)
        },
        [TCA_TAPRIO_ATTR_SCHED_ENTRY_LIST]           = { .type = NLA_NESTED },
        [TCA_TAPRIO_ATTR_SCHED_BASE_TIME]            = { .type = NLA_S64 },
        [TCA_TAPRIO_ATTR_SCHED_SINGLE_ENTRY]         = { .type = NLA_NESTED },
        [TCA_TAPRIO_ATTR_SCHED_CLOCKID]              = { .type = NLA_S32 },
        [TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME]           = { .type = NLA_S64 },
        [TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION] = { .type = NLA_S64 },
};

static int fill_sched_entry(struct nlattr **tb, struct sched_entry *entry,
                            struct netlink_ext_ack *extack)
{
        u32 interval = 0;

        if (tb[TCA_TAPRIO_SCHED_ENTRY_CMD])
                entry->command = nla_get_u8(
                        tb[TCA_TAPRIO_SCHED_ENTRY_CMD]);

        if (tb[TCA_TAPRIO_SCHED_ENTRY_GATE_MASK])
                entry->gate_mask = nla_get_u32(
                        tb[TCA_TAPRIO_SCHED_ENTRY_GATE_MASK]);

        if (tb[TCA_TAPRIO_SCHED_ENTRY_INTERVAL])
                interval = nla_get_u32(
                        tb[TCA_TAPRIO_SCHED_ENTRY_INTERVAL]);

        if (interval == 0) {
                NL_SET_ERR_MSG(extack, "Invalid interval for schedule entry");
                return -EINVAL;
        }

        entry->interval = interval;

        return 0;
}

static int parse_sched_entry(struct nlattr *n, struct sched_entry *entry,
                             int index, struct netlink_ext_ack *extack)
{
        struct nlattr *tb[TCA_TAPRIO_SCHED_ENTRY_MAX + 1] = { };
        int err;

        err = nla_parse_nested(tb, TCA_TAPRIO_SCHED_ENTRY_MAX, n,
                               entry_policy, NULL);
        if (err < 0) {
                NL_SET_ERR_MSG(extack, "Could not parse nested entry");
                return -EINVAL;
        }

        entry->index = index;

        return fill_sched_entry(tb, entry, extack);
}

static int parse_sched_list(struct nlattr *list,
                            struct sched_gate_list *sched,
                            struct netlink_ext_ack *extack)
{
        struct nlattr *n;
        int err, rem;
        int i = 0;

        if (!list)
                return -EINVAL;

        nla_for_each_nested(n, list, rem) {
                struct sched_entry *entry;

                if (nla_type(n) != TCA_TAPRIO_SCHED_ENTRY) {
                        NL_SET_ERR_MSG(extack, "Attribute is not of type 'entry'");
                        continue;
                }

                entry = kzalloc(sizeof(*entry), GFP_KERNEL);
                if (!entry) {
                        NL_SET_ERR_MSG(extack, "Not enough memory for entry");
                        return -ENOMEM;
                }

                err = parse_sched_entry(n, entry, i, extack);
                if (err < 0) {
                        kfree(entry);
                        return err;
                }

                list_add_tail(&entry->list, &sched->entries);
                i++;
        }

        sched->num_entries = i;

        return i;
}

static int parse_taprio_schedule(struct nlattr **tb,
                                 struct sched_gate_list *new,
                                 struct netlink_ext_ack *extack)
{
        int err = 0;

        if (tb[TCA_TAPRIO_ATTR_SCHED_SINGLE_ENTRY]) {
                NL_SET_ERR_MSG(extack, "Adding a single entry is not supported");
                return -ENOTSUPP;
        }

        if (tb[TCA_TAPRIO_ATTR_SCHED_BASE_TIME])
                new->base_time = nla_get_s64(tb[TCA_TAPRIO_ATTR_SCHED_BASE_TIME]);

        if (tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION])
                new->cycle_time_extension = nla_get_s64(tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION]);

        if (tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME])
                new->cycle_time = nla_get_s64(tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME]);

        if (tb[TCA_TAPRIO_ATTR_SCHED_ENTRY_LIST])
                err = parse_sched_list(
                        tb[TCA_TAPRIO_ATTR_SCHED_ENTRY_LIST], new, extack);
        if (err < 0)
                return err;

        return 0;
}

static int taprio_parse_mqprio_opt(struct net_device *dev,
                                   struct tc_mqprio_qopt *qopt,
                                   struct netlink_ext_ack *extack)
{
        int i, j;

        if (!qopt && !dev->num_tc) {
                NL_SET_ERR_MSG(extack, "'mqprio' configuration is necessary");
                return -EINVAL;
        }

        /* If num_tc is already set, it means that the user already
         * configured the mqprio part
         */
        if (dev->num_tc)
                return 0;

        /* Verify num_tc is not out of max range */
        if (qopt->num_tc > TC_MAX_QUEUE) {
                NL_SET_ERR_MSG(extack, "Number of traffic classes is outside valid range");
                return -EINVAL;
        }

        /* taprio imposes that traffic classes map 1:n to tx queues */
        if (qopt->num_tc > dev->num_tx_queues) {
                NL_SET_ERR_MSG(extack, "Number of traffic classes is greater than number of HW queues");
                return -EINVAL;
        }

        /* Verify priority mapping uses valid tcs */
        for (i = 0; i < TC_BITMASK + 1; i++) {
                if (qopt->prio_tc_map[i] >= qopt->num_tc) {
                        NL_SET_ERR_MSG(extack, "Invalid traffic class in priority to traffic class mapping");
                        return -EINVAL;
                }
        }

        for (i = 0; i < qopt->num_tc; i++) {
                unsigned int last = qopt->offset[i] + qopt->count[i];

                /* Verify the queue count is in tx range being equal to the
                 * real_num_tx_queues indicates the last queue is in use.
                 */
                if (qopt->offset[i] >= dev->num_tx_queues ||
                    !qopt->count[i] ||
                    last > dev->real_num_tx_queues) {
                        NL_SET_ERR_MSG(extack, "Invalid queue in traffic class to queue mapping");
                        return -EINVAL;
                }

                /* Verify that the offset and counts do not overlap */
                for (j = i + 1; j < qopt->num_tc; j++) {
                        if (last > qopt->offset[j]) {
                                NL_SET_ERR_MSG(extack, "Detected overlap in the traffic class to queue mapping");
                                return -EINVAL;
                        }
                }
        }

        return 0;
}

static int taprio_get_start_time(struct Qdisc *sch,
                                 struct sched_gate_list *sched,
                                 ktime_t *start)
{
        struct taprio_sched *q = qdisc_priv(sch);
        ktime_t now, base, cycle;
        s64 n;

        base = sched_base_time(sched);
        now = q->get_time();

        if (ktime_after(base, now)) {
                *start = base;
                return 0;
        }

        cycle = get_cycle_time(sched);

        /* The qdisc is expected to have at least one sched_entry.  Moreover,
         * any entry must have 'interval' > 0. Thus if the cycle time is zero,
         * something went really wrong. In that case, we should warn about this
         * inconsistent state and return error.
         */
        if (WARN_ON(!cycle))
                return -EFAULT;

        /* Schedule the start time for the beginning of the next
         * cycle.
         */
        n = div64_s64(ktime_sub_ns(now, base), cycle);
        *start = ktime_add_ns(base, (n + 1) * cycle);
        return 0;
}

static void setup_first_close_time(struct taprio_sched *q,
                                   struct sched_gate_list *sched, ktime_t base)
{
        struct sched_entry *first;
        ktime_t cycle;

        first = list_first_entry(&sched->entries,
                                 struct sched_entry, list);

        cycle = get_cycle_time(sched);

        /* FIXME: find a better place to do this */
        sched->cycle_close_time = ktime_add_ns(base, cycle);

        first->close_time = ktime_add_ns(base, first->interval);
        taprio_set_budget(q, first);
        rcu_assign_pointer(q->current_entry, NULL);
}

static void taprio_start_sched(struct Qdisc *sch,
                               ktime_t start, struct sched_gate_list *new)
{
        struct taprio_sched *q = qdisc_priv(sch);
        ktime_t expires;

        expires = hrtimer_get_expires(&q->advance_timer);
        if (expires == 0)
                expires = KTIME_MAX;

        /* If the new schedule starts before the next expiration, we
         * reprogram it to the earliest one, so we change the admin
         * schedule to the operational one at the right time.
         */
        start = min_t(ktime_t, start, expires);

        hrtimer_start(&q->advance_timer, start, HRTIMER_MODE_ABS);
}

static void taprio_set_picos_per_byte(struct net_device *dev,
                                      struct taprio_sched *q)
{
        struct ethtool_link_ksettings ecmd;
        int picos_per_byte = -1;

        if (!__ethtool_get_link_ksettings(dev, &ecmd) &&
            ecmd.base.speed != SPEED_UNKNOWN)
                picos_per_byte = div64_s64(NSEC_PER_SEC * 1000LL * 8,
                                           ecmd.base.speed * 1000 * 1000);

        atomic64_set(&q->picos_per_byte, picos_per_byte);
        netdev_dbg(dev, "taprio: set %s's picos_per_byte to: %lld, linkspeed: %d\n",
                   dev->name, (long long)atomic64_read(&q->picos_per_byte),
                   ecmd.base.speed);
}

static int taprio_dev_notifier(struct notifier_block *nb, unsigned long event,
                               void *ptr)
{
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);
        struct net_device *qdev;
        struct taprio_sched *q;
        bool found = false;

        ASSERT_RTNL();

        if (event != NETDEV_UP && event != NETDEV_CHANGE)
                return NOTIFY_DONE;

        spin_lock(&taprio_list_lock);
        list_for_each_entry(q, &taprio_list, taprio_list) {
                qdev = qdisc_dev(q->root);
                if (qdev == dev) {
                        found = true;
                        break;
                }
        }
        spin_unlock(&taprio_list_lock);

        if (found)
                taprio_set_picos_per_byte(dev, q);

        return NOTIFY_DONE;
}

static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
                         struct netlink_ext_ack *extack)
{
        struct nlattr *tb[TCA_TAPRIO_ATTR_MAX + 1] = { };
        struct sched_gate_list *oper, *admin, *new_admin;
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        struct tc_mqprio_qopt *mqprio = NULL;
        int i, err, clockid;
        unsigned long flags;
        ktime_t start;

        err = nla_parse_nested(tb, TCA_TAPRIO_ATTR_MAX, opt,
                               taprio_policy, extack);
        if (err < 0)
                return err;

        if (tb[TCA_TAPRIO_ATTR_PRIOMAP])
                mqprio = nla_data(tb[TCA_TAPRIO_ATTR_PRIOMAP]);

        err = taprio_parse_mqprio_opt(dev, mqprio, extack);
        if (err < 0)
                return err;

        new_admin = kzalloc(sizeof(*new_admin), GFP_KERNEL);
        if (!new_admin) {
                NL_SET_ERR_MSG(extack, "Not enough memory for a new schedule");
                return -ENOMEM;
        }
        INIT_LIST_HEAD(&new_admin->entries);

        rcu_read_lock();
        oper = rcu_dereference(q->oper_sched);
        admin = rcu_dereference(q->admin_sched);
        rcu_read_unlock();

        if (mqprio && (oper || admin)) {
                NL_SET_ERR_MSG(extack, "Changing the traffic mapping of a running schedule is not supported");
                err = -ENOTSUPP;
                goto free_sched;
        }

        err = parse_taprio_schedule(tb, new_admin, extack);
        if (err < 0)
                goto free_sched;

        if (new_admin->num_entries == 0) {
                NL_SET_ERR_MSG(extack, "There should be at least one entry in the schedule");
                err = -EINVAL;
                goto free_sched;
        }

        if (tb[TCA_TAPRIO_ATTR_SCHED_CLOCKID]) {
                clockid = nla_get_s32(tb[TCA_TAPRIO_ATTR_SCHED_CLOCKID]);

                /* We only support static clockids and we don't allow
                 * for it to be modified after the first init.
                 */
                if (clockid < 0 ||
                    (q->clockid != -1 && q->clockid != clockid)) {
                        NL_SET_ERR_MSG(extack, "Changing the 'clockid' of a running schedule is not supported");
                        err = -ENOTSUPP;
                        goto free_sched;
                }

                q->clockid = clockid;
        }

        if (q->clockid == -1 && !tb[TCA_TAPRIO_ATTR_SCHED_CLOCKID]) {
                NL_SET_ERR_MSG(extack, "Specifying a 'clockid' is mandatory");
                err = -EINVAL;
                goto free_sched;
        }

        taprio_set_picos_per_byte(dev, q);

        /* Protects against enqueue()/dequeue() */
        spin_lock_bh(qdisc_lock(sch));

        if (!hrtimer_active(&q->advance_timer)) {
                hrtimer_init(&q->advance_timer, q->clockid, HRTIMER_MODE_ABS);
                q->advance_timer.function = advance_sched;
        }

        if (mqprio) {
                netdev_set_num_tc(dev, mqprio->num_tc);
                for (i = 0; i < mqprio->num_tc; i++)
                        netdev_set_tc_queue(dev, i,
                                            mqprio->count[i],
                                            mqprio->offset[i]);

                /* Always use supplied priority mappings */
                for (i = 0; i < TC_BITMASK + 1; i++)
                        netdev_set_prio_tc_map(dev, i,
                                               mqprio->prio_tc_map[i]);
        }

        switch (q->clockid) {
        case CLOCK_REALTIME:
                q->get_time = ktime_get_real;
                break;
        case CLOCK_MONOTONIC:
                q->get_time = ktime_get;
                break;
        case CLOCK_BOOTTIME:
                q->get_time = ktime_get_boottime;
                break;
        case CLOCK_TAI:
                q->get_time = ktime_get_clocktai;
                break;
        default:
                NL_SET_ERR_MSG(extack, "Invalid 'clockid'");
                err = -EINVAL;
                goto unlock;
        }

        err = taprio_get_start_time(sch, new_admin, &start);
        if (err < 0) {
                NL_SET_ERR_MSG(extack, "Internal error: failed get start time");
                goto unlock;
        }

        setup_first_close_time(q, new_admin, start);

        /* Protects against advance_sched() */
        spin_lock_irqsave(&q->current_entry_lock, flags);

        taprio_start_sched(sch, start, new_admin);

        rcu_assign_pointer(q->admin_sched, new_admin);
        if (admin)
                call_rcu(&admin->rcu, taprio_free_sched_cb);
        new_admin = NULL;

        spin_unlock_irqrestore(&q->current_entry_lock, flags);

        err = 0;

unlock:
        spin_unlock_bh(qdisc_lock(sch));

free_sched:
        kfree(new_admin);

        return err;
}

static void taprio_destroy(struct Qdisc *sch)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        unsigned int i;

        spin_lock(&taprio_list_lock);
        list_del(&q->taprio_list);
        spin_unlock(&taprio_list_lock);

        hrtimer_cancel(&q->advance_timer);

        if (q->qdiscs) {
                for (i = 0; i < dev->num_tx_queues && q->qdiscs[i]; i++)
                        qdisc_put(q->qdiscs[i]);

                kfree(q->qdiscs);
        }
        q->qdiscs = NULL;

        netdev_set_num_tc(dev, 0);

        if (q->oper_sched)
                call_rcu(&q->oper_sched->rcu, taprio_free_sched_cb);

        if (q->admin_sched)
                call_rcu(&q->admin_sched->rcu, taprio_free_sched_cb);
}

static int taprio_init(struct Qdisc *sch, struct nlattr *opt,
                       struct netlink_ext_ack *extack)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        int i;

        spin_lock_init(&q->current_entry_lock);

        hrtimer_init(&q->advance_timer, CLOCK_TAI, HRTIMER_MODE_ABS);
        q->advance_timer.function = advance_sched;

        q->root = sch;

        /* We only support static clockids. Use an invalid value as default
         * and get the valid one on taprio_change().
         */
        q->clockid = -1;

        if (sch->parent != TC_H_ROOT)
                return -EOPNOTSUPP;

        if (!netif_is_multiqueue(dev))
                return -EOPNOTSUPP;

        /* pre-allocate qdisc, attachment can't fail */
        q->qdiscs = kcalloc(dev->num_tx_queues,
                            sizeof(q->qdiscs[0]),
                            GFP_KERNEL);

        if (!q->qdiscs)
                return -ENOMEM;

        if (!opt)
                return -EINVAL;

        spin_lock(&taprio_list_lock);
        list_add(&q->taprio_list, &taprio_list);
        spin_unlock(&taprio_list_lock);

        for (i = 0; i < dev->num_tx_queues; i++) {
                struct netdev_queue *dev_queue;
                struct Qdisc *qdisc;

                dev_queue = netdev_get_tx_queue(dev, i);
                qdisc = qdisc_create_dflt(dev_queue,
                                          &pfifo_qdisc_ops,
                                          TC_H_MAKE(TC_H_MAJ(sch->handle),
                                                    TC_H_MIN(i + 1)),
                                          extack);
                if (!qdisc)
                        return -ENOMEM;

                if (i < dev->real_num_tx_queues)
                        qdisc_hash_add(qdisc, false);

                q->qdiscs[i] = qdisc;
        }

        return taprio_change(sch, opt, extack);
}

static struct netdev_queue *taprio_queue_get(struct Qdisc *sch,
                                             unsigned long cl)
{
        struct net_device *dev = qdisc_dev(sch);
        unsigned long ntx = cl - 1;

        if (ntx >= dev->num_tx_queues)
                return NULL;

        return netdev_get_tx_queue(dev, ntx);
}

static int taprio_graft(struct Qdisc *sch, unsigned long cl,
                        struct Qdisc *new, struct Qdisc **old,
                        struct netlink_ext_ack *extack)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        struct netdev_queue *dev_queue = taprio_queue_get(sch, cl);

        if (!dev_queue)
                return -EINVAL;

        if (dev->flags & IFF_UP)
                dev_deactivate(dev);

        *old = q->qdiscs[cl - 1];
        q->qdiscs[cl - 1] = new;

        if (new)
                new->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;

        if (dev->flags & IFF_UP)
                dev_activate(dev);

        return 0;
}

static int dump_entry(struct sk_buff *msg,
                      const struct sched_entry *entry)
{
        struct nlattr *item;

        item = nla_nest_start(msg, TCA_TAPRIO_SCHED_ENTRY);
        if (!item)
                return -ENOSPC;

        if (nla_put_u32(msg, TCA_TAPRIO_SCHED_ENTRY_INDEX, entry->index))
                goto nla_put_failure;

        if (nla_put_u8(msg, TCA_TAPRIO_SCHED_ENTRY_CMD, entry->command))
                goto nla_put_failure;

        if (nla_put_u32(msg, TCA_TAPRIO_SCHED_ENTRY_GATE_MASK,
                        entry->gate_mask))
                goto nla_put_failure;

        if (nla_put_u32(msg, TCA_TAPRIO_SCHED_ENTRY_INTERVAL,
                        entry->interval))
                goto nla_put_failure;

        return nla_nest_end(msg, item);

nla_put_failure:
        nla_nest_cancel(msg, item);
        return -1;
}

static int dump_schedule(struct sk_buff *msg,
                         const struct sched_gate_list *root)
{
        struct nlattr *entry_list;
        struct sched_entry *entry;

        if (nla_put_s64(msg, TCA_TAPRIO_ATTR_SCHED_BASE_TIME,
                        root->base_time, TCA_TAPRIO_PAD))
                return -1;

        if (nla_put_s64(msg, TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME,
                        root->cycle_time, TCA_TAPRIO_PAD))
                return -1;

        if (nla_put_s64(msg, TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION,
                        root->cycle_time_extension, TCA_TAPRIO_PAD))
                return -1;

        entry_list = nla_nest_start(msg,
                                    TCA_TAPRIO_ATTR_SCHED_ENTRY_LIST);
        if (!entry_list)
                goto error_nest;

        list_for_each_entry(entry, &root->entries, list) {
                if (dump_entry(msg, entry) < 0)
                        goto error_nest;
        }

        nla_nest_end(msg, entry_list);
        return 0;

error_nest:
        nla_nest_cancel(msg, entry_list);
        return -1;
}

static int taprio_dump(struct Qdisc *sch, struct sk_buff *skb)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        struct sched_gate_list *oper, *admin;
        struct tc_mqprio_qopt opt = { 0 };
        struct nlattr *nest, *sched_nest;
        unsigned int i;

        rcu_read_lock();
        oper = rcu_dereference(q->oper_sched);
        admin = rcu_dereference(q->admin_sched);

        opt.num_tc = netdev_get_num_tc(dev);
        memcpy(opt.prio_tc_map, dev->prio_tc_map, sizeof(opt.prio_tc_map));

        for (i = 0; i < netdev_get_num_tc(dev); i++) {
                opt.count[i] = dev->tc_to_txq[i].count;
                opt.offset[i] = dev->tc_to_txq[i].offset;
        }

        nest = nla_nest_start(skb, TCA_OPTIONS);
        if (!nest)
                goto start_error;

        if (nla_put(skb, TCA_TAPRIO_ATTR_PRIOMAP, sizeof(opt), &opt))
                goto options_error;

        if (nla_put_s32(skb, TCA_TAPRIO_ATTR_SCHED_CLOCKID, q->clockid))
                goto options_error;

        if (oper && dump_schedule(skb, oper))
                goto options_error;

        if (!admin)
                goto done;

        sched_nest = nla_nest_start(skb, TCA_TAPRIO_ATTR_ADMIN_SCHED);
        if (!sched_nest)
                goto options_error;

        if (dump_schedule(skb, admin))
                goto admin_error;

        nla_nest_end(skb, sched_nest);

done:
        rcu_read_unlock();

        return nla_nest_end(skb, nest);

admin_error:
        nla_nest_cancel(skb, sched_nest);

options_error:
        nla_nest_cancel(skb, nest);

start_error:
        rcu_read_unlock();
        return -ENOSPC;
}

static struct Qdisc *taprio_leaf(struct Qdisc *sch, unsigned long cl)
{
        struct netdev_queue *dev_queue = taprio_queue_get(sch, cl);

        if (!dev_queue)
                return NULL;

        return dev_queue->qdisc_sleeping;
}

static unsigned long taprio_find(struct Qdisc *sch, u32 classid)
{
        unsigned int ntx = TC_H_MIN(classid);

        if (!taprio_queue_get(sch, ntx))
                return 0;
        return ntx;
}

static int taprio_dump_class(struct Qdisc *sch, unsigned long cl,
                             struct sk_buff *skb, struct tcmsg *tcm)
{
        struct netdev_queue *dev_queue = taprio_queue_get(sch, cl);

        tcm->tcm_parent = TC_H_ROOT;
        tcm->tcm_handle |= TC_H_MIN(cl);
        tcm->tcm_info = dev_queue->qdisc_sleeping->handle;

        return 0;
}

static int taprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
                                   struct gnet_dump *d)
        __releases(d->lock)
        __acquires(d->lock)
{
        struct netdev_queue *dev_queue = taprio_queue_get(sch, cl);

        sch = dev_queue->qdisc_sleeping;
        if (gnet_stats_copy_basic(&sch->running, d, NULL, &sch->bstats) < 0 ||
            qdisc_qstats_copy(d, sch) < 0)
                return -1;
        return 0;
}

static void taprio_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
        struct net_device *dev = qdisc_dev(sch);
        unsigned long ntx;

        if (arg->stop)
                return;

        arg->count = arg->skip;
        for (ntx = arg->skip; ntx < dev->num_tx_queues; ntx++) {
                if (arg->fn(sch, ntx + 1, arg) < 0) {
                        arg->stop = 1;
                        break;
                }
                arg->count++;
        }
}

static struct netdev_queue *taprio_select_queue(struct Qdisc *sch,
                                                struct tcmsg *tcm)
{
        return taprio_queue_get(sch, TC_H_MIN(tcm->tcm_parent));
}

static const struct Qdisc_class_ops taprio_class_ops = {
        .graft          = taprio_graft,
        .leaf           = taprio_leaf,
        .find           = taprio_find,
        .walk           = taprio_walk,
        .dump           = taprio_dump_class,
        .dump_stats     = taprio_dump_class_stats,
        .select_queue   = taprio_select_queue,
};

static struct Qdisc_ops taprio_qdisc_ops __read_mostly = {
        .cl_ops         = &taprio_class_ops,
        .id             = "taprio",
        .priv_size      = sizeof(struct taprio_sched),
        .init           = taprio_init,
        .change         = taprio_change,
        .destroy        = taprio_destroy,
        .peek           = taprio_peek,
        .dequeue        = taprio_dequeue,
        .enqueue        = taprio_enqueue,
        .dump           = taprio_dump,
        .owner          = THIS_MODULE,
};

static struct notifier_block taprio_device_notifier = {
        .notifier_call = taprio_dev_notifier,
};

static int __init taprio_module_init(void)
{
        int err = register_netdevice_notifier(&taprio_device_notifier);

        if (err)
                return err;

        return register_qdisc(&taprio_qdisc_ops);
}

static void __exit taprio_module_exit(void)
{
        unregister_qdisc(&taprio_qdisc_ops);
        unregister_netdevice_notifier(&taprio_device_notifier);
}

module_init(taprio_module_init);
module_exit(taprio_module_exit);
MODULE_LICENSE("GPL");