// SPDX-License-Identifier: (GPL-2.0 OR MIT)
/* Google virtual Ethernet (gve) driver
 *
 * Copyright (C) 2015-2019 Google, Inc.
 */

#include "gve.h"
#include "gve_adminq.h"
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/vmalloc.h>
#include <linux/skbuff.h>

static inline void gve_tx_put_doorbell(struct gve_priv *priv,
                                       struct gve_queue_resources *q_resources,
                                       u32 val)
{
        iowrite32be(val, &priv->db_bar2[be32_to_cpu(q_resources->db_index)]);
}

/* gvnic can only transmit from a Registered Segment.
 * We copy skb payloads into the registered segment before writing Tx
 * descriptors and ringing the Tx doorbell.
 *
 * gve_tx_fifo_* manages the Registered Segment as a FIFO - clients must
 * free allocations in the order they were allocated.
 */

static int gve_tx_fifo_init(struct gve_priv *priv, struct gve_tx_fifo *fifo)
{
        fifo->base = vmap(fifo->qpl->pages, fifo->qpl->num_entries, VM_MAP,
                          PAGE_KERNEL);
        if (unlikely(!fifo->base)) {
                netif_err(priv, drv, priv->dev, "Failed to vmap fifo, qpl_id = %d\n",
                          fifo->qpl->id);
                return -ENOMEM;
        }

        fifo->size = fifo->qpl->num_entries * PAGE_SIZE;
        atomic_set(&fifo->available, fifo->size);
        fifo->head = 0;
        return 0;
}

static void gve_tx_fifo_release(struct gve_priv *priv, struct gve_tx_fifo *fifo)
{
        WARN(atomic_read(&fifo->available) != fifo->size,
             "Releasing non-empty fifo");

        vunmap(fifo->base);
}

static int gve_tx_fifo_pad_alloc_one_frag(struct gve_tx_fifo *fifo,
                                          size_t bytes)
{
        return (fifo->head + bytes < fifo->size) ? 0 : fifo->size - fifo->head;
}

static bool gve_tx_fifo_can_alloc(struct gve_tx_fifo *fifo, size_t bytes)
{
        return (atomic_read(&fifo->available) <= bytes) ? false : true;
}

/* gve_tx_alloc_fifo - Allocate fragment(s) from Tx FIFO
 * @fifo: FIFO to allocate from
 * @bytes: Allocation size
 * @iov: Scatter-gather elements to fill with allocation fragment base/len
 *
 * Returns number of valid elements in iov[] or negative on error.
 *
 * Allocations from a given FIFO must be externally synchronized but concurrent
 * allocation and frees are allowed.
 */
static int gve_tx_alloc_fifo(struct gve_tx_fifo *fifo, size_t bytes,
                             struct gve_tx_iovec iov[2])
{
        size_t overflow, padding;
        u32 aligned_head;
        int nfrags = 0;

        if (!bytes)
                return 0;

        /* This check happens before we know how much padding is needed to
         * align to a cacheline boundary for the payload, but that is fine,
         * because the FIFO head always start aligned, and the FIFO's boundaries
         * are aligned, so if there is space for the data, there is space for
         * the padding to the next alignment.
         */
        WARN(!gve_tx_fifo_can_alloc(fifo, bytes),
             "Reached %s when there's not enough space in the fifo", __func__);

        nfrags++;

        iov[0].iov_offset = fifo->head;
        iov[0].iov_len = bytes;
        fifo->head += bytes;

        if (fifo->head > fifo->size) {
                /* If the allocation did not fit in the tail fragment of the
                 * FIFO, also use the head fragment.
                 */
                nfrags++;
                overflow = fifo->head - fifo->size;
                iov[0].iov_len -= overflow;
                iov[1].iov_offset = 0;  /* Start of fifo*/
                iov[1].iov_len = overflow;

                fifo->head = overflow;
        }

        /* Re-align to a cacheline boundary */
        aligned_head = L1_CACHE_ALIGN(fifo->head);
        padding = aligned_head - fifo->head;
        iov[nfrags - 1].iov_padding = padding;
        atomic_sub(bytes + padding, &fifo->available);
        fifo->head = aligned_head;

        if (fifo->head == fifo->size)
                fifo->head = 0;

        return nfrags;
}

/* gve_tx_free_fifo - Return space to Tx FIFO
 * @fifo: FIFO to return fragments to
 * @bytes: Bytes to free
 */
static void gve_tx_free_fifo(struct gve_tx_fifo *fifo, size_t bytes)
{
        atomic_add(bytes, &fifo->available);
}

static void gve_tx_remove_from_block(struct gve_priv *priv, int queue_idx)
{
        struct gve_notify_block *block =
                        &priv->ntfy_blocks[gve_tx_idx_to_ntfy(priv, queue_idx)];

        block->tx = NULL;
}

static int gve_clean_tx_done(struct gve_priv *priv, struct gve_tx_ring *tx,
                             u32 to_do, bool try_to_wake);

static void gve_tx_free_ring(struct gve_priv *priv, int idx)
{
        struct gve_tx_ring *tx = &priv->tx[idx];
        struct device *hdev = &priv->pdev->dev;
        size_t bytes;
        u32 slots;

        gve_tx_remove_from_block(priv, idx);
        slots = tx->mask + 1;
        gve_clean_tx_done(priv, tx, tx->req, false);
        netdev_tx_reset_queue(tx->netdev_txq);

        dma_free_coherent(hdev, sizeof(*tx->q_resources),
                          tx->q_resources, tx->q_resources_bus);
        tx->q_resources = NULL;

        gve_tx_fifo_release(priv, &tx->tx_fifo);
        gve_unassign_qpl(priv, tx->tx_fifo.qpl->id);
        tx->tx_fifo.qpl = NULL;

        bytes = sizeof(*tx->desc) * slots;
        dma_free_coherent(hdev, bytes, tx->desc, tx->bus);
        tx->desc = NULL;

        vfree(tx->info);
        tx->info = NULL;

        netif_dbg(priv, drv, priv->dev, "freed tx queue %d\n", idx);
}

static void gve_tx_add_to_block(struct gve_priv *priv, int queue_idx)
{
        int ntfy_idx = gve_tx_idx_to_ntfy(priv, queue_idx);
        struct gve_notify_block *block = &priv->ntfy_blocks[ntfy_idx];
        struct gve_tx_ring *tx = &priv->tx[queue_idx];

        block->tx = tx;
        tx->ntfy_id = ntfy_idx;
}

static int gve_tx_alloc_ring(struct gve_priv *priv, int idx)
{
        struct gve_tx_ring *tx = &priv->tx[idx];
        struct device *hdev = &priv->pdev->dev;
        u32 slots = priv->tx_desc_cnt;
        size_t bytes;

        /* Make sure everything is zeroed to start */
        memset(tx, 0, sizeof(*tx));
        tx->q_num = idx;

        tx->mask = slots - 1;

        /* alloc metadata */
        tx->info = vzalloc(sizeof(*tx->info) * slots);
        if (!tx->info)
                return -ENOMEM;

        /* alloc tx queue */
        bytes = sizeof(*tx->desc) * slots;
        tx->desc = dma_alloc_coherent(hdev, bytes, &tx->bus, GFP_KERNEL);
        if (!tx->desc)
                goto abort_with_info;

        tx->tx_fifo.qpl = gve_assign_tx_qpl(priv);

        /* map Tx FIFO */
        if (gve_tx_fifo_init(priv, &tx->tx_fifo))
                goto abort_with_desc;

        tx->q_resources =
                dma_alloc_coherent(hdev,
                                   sizeof(*tx->q_resources),
                                   &tx->q_resources_bus,
                                   GFP_KERNEL);
        if (!tx->q_resources)
                goto abort_with_fifo;

        netif_dbg(priv, drv, priv->dev, "tx[%d]->bus=%lx\n", idx,
                  (unsigned long)tx->bus);
        tx->netdev_txq = netdev_get_tx_queue(priv->dev, idx);
        gve_tx_add_to_block(priv, idx);

        return 0;

abort_with_fifo:
        gve_tx_fifo_release(priv, &tx->tx_fifo);
abort_with_desc:
        dma_free_coherent(hdev, bytes, tx->desc, tx->bus);
        tx->desc = NULL;
abort_with_info:
        vfree(tx->info);
        tx->info = NULL;
        return -ENOMEM;
}

int gve_tx_alloc_rings(struct gve_priv *priv)
{
        int err = 0;
        int i;

        for (i = 0; i < priv->tx_cfg.num_queues; i++) {
                err = gve_tx_alloc_ring(priv, i);
                if (err) {
                        netif_err(priv, drv, priv->dev,
                                  "Failed to alloc tx ring=%d: err=%d\n",
                                  i, err);
                        break;
                }
        }
        /* Unallocate if there was an error */
        if (err) {
                int j;

                for (j = 0; j < i; j++)
                        gve_tx_free_ring(priv, j);
        }
        return err;
}

void gve_tx_free_rings(struct gve_priv *priv)
{
        int i;

        for (i = 0; i < priv->tx_cfg.num_queues; i++)
                gve_tx_free_ring(priv, i);
}

/* gve_tx_avail - Calculates the number of slots available in the ring
 * @tx: tx ring to check
 *
 * Returns the number of slots available
 *
 * The capacity of the queue is mask + 1. We don't need to reserve an entry.
 **/
static inline u32 gve_tx_avail(struct gve_tx_ring *tx)
{
        return tx->mask + 1 - (tx->req - tx->done);
}

static inline int gve_skb_fifo_bytes_required(struct gve_tx_ring *tx,
                                              struct sk_buff *skb)
{
        int pad_bytes, align_hdr_pad;
        int bytes;
        int hlen;

        hlen = skb_is_gso(skb) ? skb_checksum_start_offset(skb) +
                                 tcp_hdrlen(skb) : skb_headlen(skb);

        pad_bytes = gve_tx_fifo_pad_alloc_one_frag(&tx->tx_fifo,
                                                   hlen);
        /* We need to take into account the header alignment padding. */
        align_hdr_pad = L1_CACHE_ALIGN(hlen) - hlen;
        bytes = align_hdr_pad + pad_bytes + skb->len;

        return bytes;
}

/* The most descriptors we could need are 3 - 1 for the headers, 1 for
 * the beginning of the payload at the end of the FIFO, and 1 if the
 * payload wraps to the beginning of the FIFO.
 */
#define MAX_TX_DESC_NEEDED      3

/* Check if sufficient resources (descriptor ring space, FIFO space) are
 * available to transmit the given number of bytes.
 */
static inline bool gve_can_tx(struct gve_tx_ring *tx, int bytes_required)
{
        return (gve_tx_avail(tx) >= MAX_TX_DESC_NEEDED &&
                gve_tx_fifo_can_alloc(&tx->tx_fifo, bytes_required));
}

/* Stops the queue if the skb cannot be transmitted. */
static int gve_maybe_stop_tx(struct gve_tx_ring *tx, struct sk_buff *skb)
{
        int bytes_required;

        bytes_required = gve_skb_fifo_bytes_required(tx, skb);
        if (likely(gve_can_tx(tx, bytes_required)))
                return 0;

        /* No space, so stop the queue */
        tx->stop_queue++;
        netif_tx_stop_queue(tx->netdev_txq);
        smp_mb();       /* sync with restarting queue in gve_clean_tx_done() */

        /* Now check for resources again, in case gve_clean_tx_done() freed
         * resources after we checked and we stopped the queue after
         * gve_clean_tx_done() checked.
         *
         * gve_maybe_stop_tx()                  gve_clean_tx_done()
         *   nsegs/can_alloc test failed
         *                                        gve_tx_free_fifo()
         *                                        if (tx queue stopped)
         *                                          netif_tx_queue_wake()
         *   netif_tx_stop_queue()
         *   Need to check again for space here!
         */
        if (likely(!gve_can_tx(tx, bytes_required)))
                return -EBUSY;

        netif_tx_start_queue(tx->netdev_txq);
        tx->wake_queue++;
        return 0;
}

static void gve_tx_fill_pkt_desc(union gve_tx_desc *pkt_desc,
                                 struct sk_buff *skb, bool is_gso,
                                 int l4_hdr_offset, u32 desc_cnt,
                                 u16 hlen, u64 addr)
{
        /* l4_hdr_offset and csum_offset are in units of 16-bit words */
        if (is_gso) {
                pkt_desc->pkt.type_flags = GVE_TXD_TSO | GVE_TXF_L4CSUM;
                pkt_desc->pkt.l4_csum_offset = skb->csum_offset >> 1;
                pkt_desc->pkt.l4_hdr_offset = l4_hdr_offset >> 1;
        } else if (likely(skb->ip_summed == CHECKSUM_PARTIAL)) {
                pkt_desc->pkt.type_flags = GVE_TXD_STD | GVE_TXF_L4CSUM;
                pkt_desc->pkt.l4_csum_offset = skb->csum_offset >> 1;
                pkt_desc->pkt.l4_hdr_offset = l4_hdr_offset >> 1;
        } else {
                pkt_desc->pkt.type_flags = GVE_TXD_STD;
                pkt_desc->pkt.l4_csum_offset = 0;
                pkt_desc->pkt.l4_hdr_offset = 0;
        }
        pkt_desc->pkt.desc_cnt = desc_cnt;
        pkt_desc->pkt.len = cpu_to_be16(skb->len);
        pkt_desc->pkt.seg_len = cpu_to_be16(hlen);
        pkt_desc->pkt.seg_addr = cpu_to_be64(addr);
}

static void gve_tx_fill_seg_desc(union gve_tx_desc *seg_desc,
                                 struct sk_buff *skb, bool is_gso,
                                 u16 len, u64 addr)
{
        seg_desc->seg.type_flags = GVE_TXD_SEG;
        if (is_gso) {
                if (skb_is_gso_v6(skb))
                        seg_desc->seg.type_flags |= GVE_TXSF_IPV6;
                seg_desc->seg.l3_offset = skb_network_offset(skb) >> 1;
                seg_desc->seg.mss = cpu_to_be16(skb_shinfo(skb)->gso_size);
        }
        seg_desc->seg.seg_len = cpu_to_be16(len);
        seg_desc->seg.seg_addr = cpu_to_be64(addr);
}

static int gve_tx_add_skb(struct gve_tx_ring *tx, struct sk_buff *skb)
{
        int pad_bytes, hlen, hdr_nfrags, payload_nfrags, l4_hdr_offset;
        union gve_tx_desc *pkt_desc, *seg_desc;
        struct gve_tx_buffer_state *info;
        bool is_gso = skb_is_gso(skb);
        u32 idx = tx->req & tx->mask;
        int payload_iov = 2;
        int copy_offset;
        u32 next_idx;
        int i;

        info = &tx->info[idx];
        pkt_desc = &tx->desc[idx];

        l4_hdr_offset = skb_checksum_start_offset(skb);
        /* If the skb is gso, then we want the tcp header in the first segment
         * otherwise we want the linear portion of the skb (which will contain
         * the checksum because skb->csum_start and skb->csum_offset are given
         * relative to skb->head) in the first segment.
         */
        hlen = is_gso ? l4_hdr_offset + tcp_hdrlen(skb) :
                        skb_headlen(skb);

        info->skb =  skb;
        /* We don't want to split the header, so if necessary, pad to the end
         * of the fifo and then put the header at the beginning of the fifo.
         */
        pad_bytes = gve_tx_fifo_pad_alloc_one_frag(&tx->tx_fifo, hlen);
        hdr_nfrags = gve_tx_alloc_fifo(&tx->tx_fifo, hlen + pad_bytes,
                                       &info->iov[0]);
        WARN(!hdr_nfrags, "hdr_nfrags should never be 0!");
        payload_nfrags = gve_tx_alloc_fifo(&tx->tx_fifo, skb->len - hlen,
                                           &info->iov[payload_iov]);

        gve_tx_fill_pkt_desc(pkt_desc, skb, is_gso, l4_hdr_offset,
                             1 + payload_nfrags, hlen,
                             info->iov[hdr_nfrags - 1].iov_offset);

        skb_copy_bits(skb, 0,
                      tx->tx_fifo.base + info->iov[hdr_nfrags - 1].iov_offset,
                      hlen);
        copy_offset = hlen;

        for (i = payload_iov; i < payload_nfrags + payload_iov; i++) {
                next_idx = (tx->req + 1 + i - payload_iov) & tx->mask;
                seg_desc = &tx->desc[next_idx];

                gve_tx_fill_seg_desc(seg_desc, skb, is_gso,
                                     info->iov[i].iov_len,
                                     info->iov[i].iov_offset);

                skb_copy_bits(skb, copy_offset,
                              tx->tx_fifo.base + info->iov[i].iov_offset,
                              info->iov[i].iov_len);
                copy_offset += info->iov[i].iov_len;
        }

        return 1 + payload_nfrags;
}

netdev_tx_t gve_tx(struct sk_buff *skb, struct net_device *dev)
{
        struct gve_priv *priv = netdev_priv(dev);
        struct gve_tx_ring *tx;
        int nsegs;

        WARN(skb_get_queue_mapping(skb) > priv->tx_cfg.num_queues,
             "skb queue index out of range");
        tx = &priv->tx[skb_get_queue_mapping(skb)];
        if (unlikely(gve_maybe_stop_tx(tx, skb))) {
                /* We need to ring the txq doorbell -- we have stopped the Tx
                 * queue for want of resources, but prior calls to gve_tx()
                 * may have added descriptors without ringing the doorbell.
                 */

                /* Ensure tx descs from a prior gve_tx are visible before
                 * ringing doorbell.
                 */
                dma_wmb();
                gve_tx_put_doorbell(priv, tx->q_resources, tx->req);
                return NETDEV_TX_BUSY;
        }
        nsegs = gve_tx_add_skb(tx, skb);

        netdev_tx_sent_queue(tx->netdev_txq, skb->len);
        skb_tx_timestamp(skb);

        /* give packets to NIC */
        tx->req += nsegs;

        if (!netif_xmit_stopped(tx->netdev_txq) && netdev_xmit_more())
                return NETDEV_TX_OK;

        /* Ensure tx descs are visible before ringing doorbell */
        dma_wmb();
        gve_tx_put_doorbell(priv, tx->q_resources, tx->req);
        return NETDEV_TX_OK;
}

#define GVE_TX_START_THRESH     PAGE_SIZE

static int gve_clean_tx_done(struct gve_priv *priv, struct gve_tx_ring *tx,
                             u32 to_do, bool try_to_wake)
{
        struct gve_tx_buffer_state *info;
        u64 pkts = 0, bytes = 0;
        size_t space_freed = 0;
        struct sk_buff *skb;
        int i, j;
        u32 idx;

        for (j = 0; j < to_do; j++) {
                idx = tx->done & tx->mask;
                netif_info(priv, tx_done, priv->dev,
                           "[%d] %s: idx=%d (req=%u done=%u)\n",
                           tx->q_num, __func__, idx, tx->req, tx->done);
                info = &tx->info[idx];
                skb = info->skb;

                /* Mark as free */
                if (skb) {
                        info->skb = NULL;
                        bytes += skb->len;
                        pkts++;
                        dev_consume_skb_any(skb);
                        /* FIFO free */
                        for (i = 0; i < ARRAY_SIZE(info->iov); i++) {
                                space_freed += info->iov[i].iov_len +
                                               info->iov[i].iov_padding;
                                info->iov[i].iov_len = 0;
                                info->iov[i].iov_padding = 0;
                        }
                }
                tx->done++;
        }

        gve_tx_free_fifo(&tx->tx_fifo, space_freed);
        u64_stats_update_begin(&tx->statss);
        tx->bytes_done += bytes;
        tx->pkt_done += pkts;
        u64_stats_update_end(&tx->statss);
        netdev_tx_completed_queue(tx->netdev_txq, pkts, bytes);

        /* start the queue if we've stopped it */
#ifndef CONFIG_BQL
        /* Make sure that the doorbells are synced */
        smp_mb();
#endif
        if (try_to_wake && netif_tx_queue_stopped(tx->netdev_txq) &&
            likely(gve_can_tx(tx, GVE_TX_START_THRESH))) {
                tx->wake_queue++;
                netif_tx_wake_queue(tx->netdev_txq);
        }

        return pkts;
}

__be32 gve_tx_load_event_counter(struct gve_priv *priv,
                                 struct gve_tx_ring *tx)
{
        u32 counter_index = be32_to_cpu((tx->q_resources->counter_index));

        return READ_ONCE(priv->counter_array[counter_index]);
}

bool gve_tx_poll(struct gve_notify_block *block, int budget)
{
        struct gve_priv *priv = block->priv;
        struct gve_tx_ring *tx = block->tx;
        bool repoll = false;
        u32 nic_done;
        u32 to_do;

        /* If budget is 0, do all the work */
        if (budget == 0)
                budget = INT_MAX;

        /* Find out how much work there is to be done */
        tx->last_nic_done = gve_tx_load_event_counter(priv, tx);
        nic_done = be32_to_cpu(tx->last_nic_done);
        if (budget > 0) {
                /* Do as much work as we have that the budget will
                 * allow
                 */
                to_do = min_t(u32, (nic_done - tx->done), budget);
                gve_clean_tx_done(priv, tx, to_do, true);
        }
        /* If we still have work we want to repoll */
        repoll |= (nic_done != tx->done);
        return repoll;
}