/*
 * Copyright (c) 2012 Qualcomm Atheros, Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <linux/etherdevice.h>
#include <net/ieee80211_radiotap.h>
#include <linux/if_arp.h>
#include <linux/moduleparam.h>

#include "wil6210.h"
#include "wmi.h"
#include "txrx.h"
#include "trace.h"

static bool rtap_include_phy_info;
module_param(rtap_include_phy_info, bool, S_IRUGO);
MODULE_PARM_DESC(rtap_include_phy_info,
                 " Include PHY info in the radiotap header, default - no");

static inline int wil_vring_is_empty(struct vring *vring)
{
        return vring->swhead == vring->swtail;
}

static inline u32 wil_vring_next_tail(struct vring *vring)
{
        return (vring->swtail + 1) % vring->size;
}

static inline void wil_vring_advance_head(struct vring *vring, int n)
{
        vring->swhead = (vring->swhead + n) % vring->size;
}

static inline int wil_vring_is_full(struct vring *vring)
{
        return wil_vring_next_tail(vring) == vring->swhead;
}
/*
 * Available space in Tx Vring
 */
static inline int wil_vring_avail_tx(struct vring *vring)
{
        u32 swhead = vring->swhead;
        u32 swtail = vring->swtail;
        int used = (vring->size + swhead - swtail) % vring->size;

        return vring->size - used - 1;
}

static int wil_vring_alloc(struct wil6210_priv *wil, struct vring *vring)
{
        struct device *dev = wil_to_dev(wil);
        size_t sz = vring->size * sizeof(vring->va[0]);
        uint i;

        BUILD_BUG_ON(sizeof(vring->va[0]) != 32);

        vring->swhead = 0;
        vring->swtail = 0;
        vring->ctx = kzalloc(vring->size * sizeof(vring->ctx[0]), GFP_KERNEL);
        if (!vring->ctx) {
                vring->va = NULL;
                return -ENOMEM;
        }
        /*
         * vring->va should be aligned on its size rounded up to power of 2
         * This is granted by the dma_alloc_coherent
         */
        vring->va = dma_alloc_coherent(dev, sz, &vring->pa, GFP_KERNEL);
        if (!vring->va) {
                kfree(vring->ctx);
                vring->ctx = NULL;
                return -ENOMEM;
        }
        /* initially, all descriptors are SW owned
         * For Tx and Rx, ownership bit is at the same location, thus
         * we can use any
         */
        for (i = 0; i < vring->size; i++) {
                volatile struct vring_tx_desc *_d = &(vring->va[i].tx);
                _d->dma.status = TX_DMA_STATUS_DU;
        }

        wil_dbg_misc(wil, "vring[%d] 0x%p:0x%016llx 0x%p\n", vring->size,
                     vring->va, (unsigned long long)vring->pa, vring->ctx);

        return 0;
}

static void wil_vring_free(struct wil6210_priv *wil, struct vring *vring,
                           int tx)
{
        struct device *dev = wil_to_dev(wil);
        size_t sz = vring->size * sizeof(vring->va[0]);

        while (!wil_vring_is_empty(vring)) {
                dma_addr_t pa;
                struct sk_buff *skb;
                u16 dmalen;

                if (tx) {
                        struct vring_tx_desc dd, *d = &dd;
                        volatile struct vring_tx_desc *_d =
                                        &vring->va[vring->swtail].tx;

                        *d = *_d;
                        pa = wil_desc_addr(&d->dma.addr);
                        dmalen = le16_to_cpu(d->dma.length);
                        skb = vring->ctx[vring->swtail];
                        if (skb) {
                                dma_unmap_single(dev, pa, dmalen,
                                                 DMA_TO_DEVICE);
                                dev_kfree_skb_any(skb);
                                vring->ctx[vring->swtail] = NULL;
                        } else {
                                dma_unmap_page(dev, pa, dmalen,
                                               DMA_TO_DEVICE);
                        }
                        vring->swtail = wil_vring_next_tail(vring);
                } else { /* rx */
                        struct vring_rx_desc dd, *d = &dd;
                        volatile struct vring_rx_desc *_d =
                                        &vring->va[vring->swtail].rx;

                        *d = *_d;
                        pa = wil_desc_addr(&d->dma.addr);
                        dmalen = le16_to_cpu(d->dma.length);
                        skb = vring->ctx[vring->swhead];
                        dma_unmap_single(dev, pa, dmalen, DMA_FROM_DEVICE);
                        kfree_skb(skb);
                        wil_vring_advance_head(vring, 1);
                }
        }
        dma_free_coherent(dev, sz, (void *)vring->va, vring->pa);
        kfree(vring->ctx);
        vring->pa = 0;
        vring->va = NULL;
        vring->ctx = NULL;
}

/**
 * Allocate one skb for Rx VRING
 *
 * Safe to call from IRQ
 */
static int wil_vring_alloc_skb(struct wil6210_priv *wil, struct vring *vring,
                               u32 i, int headroom)
{
        struct device *dev = wil_to_dev(wil);
        unsigned int sz = RX_BUF_LEN;
        struct vring_rx_desc dd, *d = &dd;
        volatile struct vring_rx_desc *_d = &(vring->va[i].rx);
        dma_addr_t pa;

        /* TODO align */
        struct sk_buff *skb = dev_alloc_skb(sz + headroom);
        if (unlikely(!skb))
                return -ENOMEM;

        skb_reserve(skb, headroom);
        skb_put(skb, sz);

        pa = dma_map_single(dev, skb->data, skb->len, DMA_FROM_DEVICE);
        if (unlikely(dma_mapping_error(dev, pa))) {
                kfree_skb(skb);
                return -ENOMEM;
        }

        d->dma.d0 = BIT(9) | RX_DMA_D0_CMD_DMA_IT;
        wil_desc_addr_set(&d->dma.addr, pa);
        /* ip_length don't care */
        /* b11 don't care */
        /* error don't care */
        d->dma.status = 0; /* BIT(0) should be 0 for HW_OWNED */
        d->dma.length = cpu_to_le16(sz);
        *_d = *d;
        vring->ctx[i] = skb;

        return 0;
}

/**
 * Adds radiotap header
 *
 * Any error indicated as "Bad FCS"
 *
 * Vendor data for 04:ce:14-1 (Wilocity-1) consists of:
 *  - Rx descriptor: 32 bytes
 *  - Phy info
 */
static void wil_rx_add_radiotap_header(struct wil6210_priv *wil,
                                       struct sk_buff *skb)
{
        struct wireless_dev *wdev = wil->wdev;
        struct wil6210_rtap {
                struct ieee80211_radiotap_header rthdr;
                /* fields should be in the order of bits in rthdr.it_present */
                /* flags */
                u8 flags;
                /* channel */
                __le16 chnl_freq __aligned(2);
                __le16 chnl_flags;
                /* MCS */
                u8 mcs_present;
                u8 mcs_flags;
                u8 mcs_index;
        } __packed;
        struct wil6210_rtap_vendor {
                struct wil6210_rtap rtap;
                /* vendor */
                u8 vendor_oui[3] __aligned(2);
                u8 vendor_ns;
                __le16 vendor_skip;
                u8 vendor_data[0];
        } __packed;
        struct vring_rx_desc *d = wil_skb_rxdesc(skb);
        struct wil6210_rtap_vendor *rtap_vendor;
        int rtap_len = sizeof(struct wil6210_rtap);
        int phy_length = 0; /* phy info header size, bytes */
        static char phy_data[128];
        struct ieee80211_channel *ch = wdev->preset_chandef.chan;

        if (rtap_include_phy_info) {
                rtap_len = sizeof(*rtap_vendor) + sizeof(*d);
                /* calculate additional length */
                if (d->dma.status & RX_DMA_STATUS_PHY_INFO) {
                        /**
                         * PHY info starts from 8-byte boundary
                         * there are 8-byte lines, last line may be partially
                         * written (HW bug), thus FW configures for last line
                         * to be excessive. Driver skips this last line.
                         */
                        int len = min_t(int, 8 + sizeof(phy_data),
                                        wil_rxdesc_phy_length(d));
                        if (len > 8) {
                                void *p = skb_tail_pointer(skb);
                                void *pa = PTR_ALIGN(p, 8);
                                if (skb_tailroom(skb) >= len + (pa - p)) {
                                        phy_length = len - 8;
                                        memcpy(phy_data, pa, phy_length);
                                }
                        }
                }
                rtap_len += phy_length;
        }

        if (skb_headroom(skb) < rtap_len &&
            pskb_expand_head(skb, rtap_len, 0, GFP_ATOMIC)) {
                wil_err(wil, "Unable to expand headrom to %d\n", rtap_len);
                return;
        }

        rtap_vendor = (void *)skb_push(skb, rtap_len);
        memset(rtap_vendor, 0, rtap_len);

        rtap_vendor->rtap.rthdr.it_version = PKTHDR_RADIOTAP_VERSION;
        rtap_vendor->rtap.rthdr.it_len = cpu_to_le16(rtap_len);
        rtap_vendor->rtap.rthdr.it_present = cpu_to_le32(
                        (1 << IEEE80211_RADIOTAP_FLAGS) |
                        (1 << IEEE80211_RADIOTAP_CHANNEL) |
                        (1 << IEEE80211_RADIOTAP_MCS));
        if (d->dma.status & RX_DMA_STATUS_ERROR)
                rtap_vendor->rtap.flags |= IEEE80211_RADIOTAP_F_BADFCS;

        rtap_vendor->rtap.chnl_freq = cpu_to_le16(ch ? ch->center_freq : 58320);
        rtap_vendor->rtap.chnl_flags = cpu_to_le16(0);

        rtap_vendor->rtap.mcs_present = IEEE80211_RADIOTAP_MCS_HAVE_MCS;
        rtap_vendor->rtap.mcs_flags = 0;
        rtap_vendor->rtap.mcs_index = wil_rxdesc_mcs(d);

        if (rtap_include_phy_info) {
                rtap_vendor->rtap.rthdr.it_present |= cpu_to_le32(1 <<
                                IEEE80211_RADIOTAP_VENDOR_NAMESPACE);
                /* OUI for Wilocity 04:ce:14 */
                rtap_vendor->vendor_oui[0] = 0x04;
                rtap_vendor->vendor_oui[1] = 0xce;
                rtap_vendor->vendor_oui[2] = 0x14;
                rtap_vendor->vendor_ns = 1;
                /* Rx descriptor + PHY data  */
                rtap_vendor->vendor_skip = cpu_to_le16(sizeof(*d) +
                                                       phy_length);
                memcpy(rtap_vendor->vendor_data, (void *)d, sizeof(*d));
                memcpy(rtap_vendor->vendor_data + sizeof(*d), phy_data,
                       phy_length);
        }
}

/*
 * Fast swap in place between 2 registers
 */
static void wil_swap_u16(u16 *a, u16 *b)
{
        *a ^= *b;
        *b ^= *a;
        *a ^= *b;
}

static void wil_swap_ethaddr(void *data)
{
        struct ethhdr *eth = data;
        u16 *s = (u16 *)eth->h_source;
        u16 *d = (u16 *)eth->h_dest;

        wil_swap_u16(s++, d++);
        wil_swap_u16(s++, d++);
        wil_swap_u16(s, d);
}

/**
 * reap 1 frame from @swhead
 *
 * Rx descriptor copied to skb->cb
 *
 * Safe to call from IRQ
 */
static struct sk_buff *wil_vring_reap_rx(struct wil6210_priv *wil,
                                         struct vring *vring)
{
        struct device *dev = wil_to_dev(wil);
        struct net_device *ndev = wil_to_ndev(wil);
        volatile struct vring_rx_desc *_d;
        struct vring_rx_desc *d;
        struct sk_buff *skb;
        dma_addr_t pa;
        unsigned int sz = RX_BUF_LEN;
        u16 dmalen;
        u8 ftype;
        u8 ds_bits;

        BUILD_BUG_ON(sizeof(struct vring_rx_desc) > sizeof(skb->cb));

        if (wil_vring_is_empty(vring))
                return NULL;

        _d = &(vring->va[vring->swhead].rx);
        if (!(_d->dma.status & RX_DMA_STATUS_DU)) {
                /* it is not error, we just reached end of Rx done area */
                return NULL;
        }

        skb = vring->ctx[vring->swhead];
        d = wil_skb_rxdesc(skb);
        *d = *_d;
        pa = wil_desc_addr(&d->dma.addr);
        vring->ctx[vring->swhead] = NULL;
        wil_vring_advance_head(vring, 1);

        dma_unmap_single(dev, pa, sz, DMA_FROM_DEVICE);
        dmalen = le16_to_cpu(d->dma.length);

        trace_wil6210_rx(vring->swhead, d);
        wil_dbg_txrx(wil, "Rx[%3d] : %d bytes\n", vring->swhead, dmalen);
        wil_hex_dump_txrx("Rx ", DUMP_PREFIX_NONE, 32, 4,
                          (const void *)d, sizeof(*d), false);

        if (dmalen > sz) {
                wil_err(wil, "Rx size too large: %d bytes!\n", dmalen);
                kfree_skb(skb);
                return NULL;
        }
        skb_trim(skb, dmalen);

        wil_hex_dump_txrx("Rx ", DUMP_PREFIX_OFFSET, 16, 1,
                          skb->data, skb_headlen(skb), false);


        wil->stats.last_mcs_rx = wil_rxdesc_mcs(d);

        /* use radiotap header only if required */
        if (ndev->type == ARPHRD_IEEE80211_RADIOTAP)
                wil_rx_add_radiotap_header(wil, skb);

        /* no extra checks if in sniffer mode */
        if (ndev->type != ARPHRD_ETHER)
                return skb;
        /*
         * Non-data frames may be delivered through Rx DMA channel (ex: BAR)
         * Driver should recognize it by frame type, that is found
         * in Rx descriptor. If type is not data, it is 802.11 frame as is
         */
        ftype = wil_rxdesc_ftype(d) << 2;
        if (ftype != IEEE80211_FTYPE_DATA) {
                wil_dbg_txrx(wil, "Non-data frame ftype 0x%08x\n", ftype);
                /* TODO: process it */
                kfree_skb(skb);
                return NULL;
        }

        if (skb->len < ETH_HLEN) {
                wil_err(wil, "Short frame, len = %d\n", skb->len);
                /* TODO: process it (i.e. BAR) */
                kfree_skb(skb);
                return NULL;
        }

        ds_bits = wil_rxdesc_ds_bits(d);
        if (ds_bits == 1) {
                /*
                 * HW bug - in ToDS mode, i.e. Rx on AP side,
                 * addresses get swapped
                 */
                wil_swap_ethaddr(skb->data);
        }

        return skb;
}

/**
 * allocate and fill up to @count buffers in rx ring
 * buffers posted at @swtail
 */
static int wil_rx_refill(struct wil6210_priv *wil, int count)
{
        struct net_device *ndev = wil_to_ndev(wil);
        struct vring *v = &wil->vring_rx;
        u32 next_tail;
        int rc = 0;
        int headroom = ndev->type == ARPHRD_IEEE80211_RADIOTAP ?
                        WIL6210_RTAP_SIZE : 0;

        for (; next_tail = wil_vring_next_tail(v),
                        (next_tail != v->swhead) && (count-- > 0);
                        v->swtail = next_tail) {
                rc = wil_vring_alloc_skb(wil, v, v->swtail, headroom);
                if (rc) {
                        wil_err(wil, "Error %d in wil_rx_refill[%d]\n",
                                rc, v->swtail);
                        break;
                }
        }
        iowrite32(v->swtail, wil->csr + HOSTADDR(v->hwtail));

        return rc;
}

/*
 * Pass Rx packet to the netif. Update statistics.
 * Called in softirq context (NAPI poll).
 */
static void wil_netif_rx_any(struct sk_buff *skb, struct net_device *ndev)
{
        int rc;
        unsigned int len = skb->len;

        skb_orphan(skb);

        rc = netif_receive_skb(skb);

        if (likely(rc == NET_RX_SUCCESS)) {
                ndev->stats.rx_packets++;
                ndev->stats.rx_bytes += len;

        } else {
                ndev->stats.rx_dropped++;
        }
}

/**
 * Proceed all completed skb's from Rx VRING
 *
 * Safe to call from NAPI poll, i.e. softirq with interrupts enabled
 */
void wil_rx_handle(struct wil6210_priv *wil, int *quota)
{
        struct net_device *ndev = wil_to_ndev(wil);
        struct vring *v = &wil->vring_rx;
        struct sk_buff *skb;

        if (!v->va) {
                wil_err(wil, "Rx IRQ while Rx not yet initialized\n");
                return;
        }
        wil_dbg_txrx(wil, "%s()\n", __func__);
        while ((*quota > 0) && (NULL != (skb = wil_vring_reap_rx(wil, v)))) {
                (*quota)--;

                if (wil->wdev->iftype == NL80211_IFTYPE_MONITOR) {
                        skb->dev = ndev;
                        skb_reset_mac_header(skb);
                        skb->ip_summed = CHECKSUM_UNNECESSARY;
                        skb->pkt_type = PACKET_OTHERHOST;
                        skb->protocol = htons(ETH_P_802_2);

                } else {
                        skb->protocol = eth_type_trans(skb, ndev);
                }

                wil_netif_rx_any(skb, ndev);
        }
        wil_rx_refill(wil, v->size);
}

int wil_rx_init(struct wil6210_priv *wil)
{
        struct vring *vring = &wil->vring_rx;
        int rc;

        vring->size = WIL6210_RX_RING_SIZE;
        rc = wil_vring_alloc(wil, vring);
        if (rc)
                return rc;

        rc = wmi_rx_chain_add(wil, vring);
        if (rc)
                goto err_free;

        rc = wil_rx_refill(wil, vring->size);
        if (rc)
                goto err_free;

        return 0;
 err_free:
        wil_vring_free(wil, vring, 0);

        return rc;
}

void wil_rx_fini(struct wil6210_priv *wil)
{
        struct vring *vring = &wil->vring_rx;

        if (vring->va)
                wil_vring_free(wil, vring, 0);
}

int wil_vring_init_tx(struct wil6210_priv *wil, int id, int size,
                      int cid, int tid)
{
        int rc;
        struct wmi_vring_cfg_cmd cmd = {
                .action = cpu_to_le32(WMI_VRING_CMD_ADD),
                .vring_cfg = {
                        .tx_sw_ring = {
                                .max_mpdu_size = cpu_to_le16(TX_BUF_LEN),
                                .ring_size = cpu_to_le16(size),
                        },
                        .ringid = id,
                        .cidxtid = (cid & 0xf) | ((tid & 0xf) << 4),
                        .encap_trans_type = WMI_VRING_ENC_TYPE_802_3,
                        .mac_ctrl = 0,
                        .to_resolution = 0,
                        .agg_max_wsize = 16,
                        .schd_params = {
                                .priority = cpu_to_le16(0),
                                .timeslot_us = cpu_to_le16(0xfff),
                        },
                },
        };
        struct {
                struct wil6210_mbox_hdr_wmi wmi;
                struct wmi_vring_cfg_done_event cmd;
        } __packed reply;
        struct vring *vring = &wil->vring_tx[id];

        if (vring->va) {
                wil_err(wil, "Tx ring [%d] already allocated\n", id);
                rc = -EINVAL;
                goto out;
        }

        vring->size = size;
        rc = wil_vring_alloc(wil, vring);
        if (rc)
                goto out;

        cmd.vring_cfg.tx_sw_ring.ring_mem_base = cpu_to_le64(vring->pa);

        rc = wmi_call(wil, WMI_VRING_CFG_CMDID, &cmd, sizeof(cmd),
                      WMI_VRING_CFG_DONE_EVENTID, &reply, sizeof(reply), 100);
        if (rc)
                goto out_free;

        if (reply.cmd.status != WMI_FW_STATUS_SUCCESS) {
                wil_err(wil, "Tx config failed, status 0x%02x\n",
                        reply.cmd.status);
                rc = -EINVAL;
                goto out_free;
        }
        vring->hwtail = le32_to_cpu(reply.cmd.tx_vring_tail_ptr);

        return 0;
 out_free:
        wil_vring_free(wil, vring, 1);
 out:

        return rc;
}

void wil_vring_fini_tx(struct wil6210_priv *wil, int id)
{
        struct vring *vring = &wil->vring_tx[id];

        if (!vring->va)
                return;

        wil_vring_free(wil, vring, 1);
}

static struct vring *wil_find_tx_vring(struct wil6210_priv *wil,
                                       struct sk_buff *skb)
{
        struct vring *v = &wil->vring_tx[0];

        if (v->va)
                return v;

        return NULL;
}

static int wil_tx_desc_map(struct vring_tx_desc *d, dma_addr_t pa, u32 len,
                           int vring_index)
{
        wil_desc_addr_set(&d->dma.addr, pa);
        d->dma.ip_length = 0;
        /* 0..6: mac_length; 7:ip_version 0-IP6 1-IP4*/
        d->dma.b11 = 0/*14 | BIT(7)*/;
        d->dma.error = 0;
        d->dma.status = 0; /* BIT(0) should be 0 for HW_OWNED */
        d->dma.length = cpu_to_le16((u16)len);
        d->dma.d0 = (vring_index << DMA_CFG_DESC_TX_0_QID_POS);
        d->mac.d[0] = 0;
        d->mac.d[1] = 0;
        d->mac.d[2] = 0;
        d->mac.ucode_cmd = 0;
        /* use dst index 0 */
        d->mac.d[1] |= BIT(MAC_CFG_DESC_TX_1_DST_INDEX_EN_POS) |
                       (0 << MAC_CFG_DESC_TX_1_DST_INDEX_POS);
        /* translation type:  0 - bypass; 1 - 802.3; 2 - native wifi */
        d->mac.d[2] = BIT(MAC_CFG_DESC_TX_2_SNAP_HDR_INSERTION_EN_POS) |
                      (1 << MAC_CFG_DESC_TX_2_L2_TRANSLATION_TYPE_POS);

        return 0;
}

static int wil_tx_vring(struct wil6210_priv *wil, struct vring *vring,
                        struct sk_buff *skb)
{
        struct device *dev = wil_to_dev(wil);
        struct vring_tx_desc dd, *d = &dd;
        volatile struct vring_tx_desc *_d;
        u32 swhead = vring->swhead;
        int avail = wil_vring_avail_tx(vring);
        int nr_frags = skb_shinfo(skb)->nr_frags;
        uint f;
        int vring_index = vring - wil->vring_tx;
        uint i = swhead;
        dma_addr_t pa;

        wil_dbg_txrx(wil, "%s()\n", __func__);

        if (avail < vring->size/8)
                netif_tx_stop_all_queues(wil_to_ndev(wil));
        if (avail < 1 + nr_frags) {
                wil_err(wil, "Tx ring full. No space for %d fragments\n",
                        1 + nr_frags);
                return -ENOMEM;
        }
        _d = &(vring->va[i].tx);

        /* FIXME FW can accept only unicast frames for the peer */
        memcpy(skb->data, wil->dst_addr[vring_index], ETH_ALEN);

        pa = dma_map_single(dev, skb->data,
                        skb_headlen(skb), DMA_TO_DEVICE);

        wil_dbg_txrx(wil, "Tx skb %d bytes %p -> %#08llx\n", skb_headlen(skb),
                     skb->data, (unsigned long long)pa);
        wil_hex_dump_txrx("Tx ", DUMP_PREFIX_OFFSET, 16, 1,
                          skb->data, skb_headlen(skb), false);

        if (unlikely(dma_mapping_error(dev, pa)))
                return -EINVAL;
        /* 1-st segment */
        wil_tx_desc_map(d, pa, skb_headlen(skb), vring_index);
        d->mac.d[2] |= ((nr_frags + 1) <<
                       MAC_CFG_DESC_TX_2_NUM_OF_DESCRIPTORS_POS);
        if (nr_frags)
                *_d = *d;

        /* middle segments */
        for (f = 0; f < nr_frags; f++) {
                const struct skb_frag_struct *frag =
                                &skb_shinfo(skb)->frags[f];
                int len = skb_frag_size(frag);
                i = (swhead + f + 1) % vring->size;
                _d = &(vring->va[i].tx);
                pa = skb_frag_dma_map(dev, frag, 0, skb_frag_size(frag),
                                DMA_TO_DEVICE);
                if (unlikely(dma_mapping_error(dev, pa)))
                        goto dma_error;
                wil_tx_desc_map(d, pa, len, vring_index);
                vring->ctx[i] = NULL;
                *_d = *d;
        }
        /* for the last seg only */
        d->dma.d0 |= BIT(DMA_CFG_DESC_TX_0_CMD_EOP_POS);
        d->dma.d0 |= BIT(DMA_CFG_DESC_TX_0_CMD_MARK_WB_POS);
        d->dma.d0 |= BIT(DMA_CFG_DESC_TX_0_CMD_DMA_IT_POS);
        *_d = *d;

        wil_hex_dump_txrx("Tx ", DUMP_PREFIX_NONE, 32, 4,
                          (const void *)d, sizeof(*d), false);

        /* advance swhead */
        wil_vring_advance_head(vring, nr_frags + 1);
        wil_dbg_txrx(wil, "Tx swhead %d -> %d\n", swhead, vring->swhead);
        trace_wil6210_tx(vring_index, swhead, skb->len, nr_frags);
        iowrite32(vring->swhead, wil->csr + HOSTADDR(vring->hwtail));
        /* hold reference to skb
         * to prevent skb release before accounting
         * in case of immediate "tx done"
         */
        vring->ctx[i] = skb_get(skb);

        return 0;
 dma_error:
        /* unmap what we have mapped */
        /* Note: increment @f to operate with positive index */
        for (f++; f > 0; f--) {
                u16 dmalen;

                i = (swhead + f) % vring->size;
                _d = &(vring->va[i].tx);
                *d = *_d;
                _d->dma.status = TX_DMA_STATUS_DU;
                pa = wil_desc_addr(&d->dma.addr);
                dmalen = le16_to_cpu(d->dma.length);
                if (vring->ctx[i])
                        dma_unmap_single(dev, pa, dmalen, DMA_TO_DEVICE);
                else
                        dma_unmap_page(dev, pa, dmalen, DMA_TO_DEVICE);
        }

        return -EINVAL;
}


netdev_tx_t wil_start_xmit(struct sk_buff *skb, struct net_device *ndev)
{
        struct wil6210_priv *wil = ndev_to_wil(ndev);
        struct vring *vring;
        int rc;

        wil_dbg_txrx(wil, "%s()\n", __func__);
        if (!test_bit(wil_status_fwready, &wil->status)) {
                wil_err(wil, "FW not ready\n");
                goto drop;
        }
        if (!test_bit(wil_status_fwconnected, &wil->status)) {
                wil_err(wil, "FW not connected\n");
                goto drop;
        }
        if (wil->wdev->iftype == NL80211_IFTYPE_MONITOR) {
                wil_err(wil, "Xmit in monitor mode not supported\n");
                goto drop;
        }

        /* find vring */
        vring = wil_find_tx_vring(wil, skb);
        if (!vring) {
                wil_err(wil, "No Tx VRING available\n");
                goto drop;
        }
        /* set up vring entry */
        rc = wil_tx_vring(wil, vring, skb);

        switch (rc) {
        case 0:
                /* statistics will be updated on the tx_complete */
                dev_kfree_skb_any(skb);
                return NETDEV_TX_OK;
        case -ENOMEM:
                return NETDEV_TX_BUSY;
        default:
                break; /* goto drop; */
        }
 drop:
        ndev->stats.tx_dropped++;
        dev_kfree_skb_any(skb);

        return NET_XMIT_DROP;
}

/**
 * Clean up transmitted skb's from the Tx VRING
 *
 * Return number of descriptors cleared
 *
 * Safe to call from IRQ
 */
int wil_tx_complete(struct wil6210_priv *wil, int ringid)
{
        struct net_device *ndev = wil_to_ndev(wil);
        struct device *dev = wil_to_dev(wil);
        struct vring *vring = &wil->vring_tx[ringid];
        int done = 0;

        if (!vring->va) {
                wil_err(wil, "Tx irq[%d]: vring not initialized\n", ringid);
                return 0;
        }

        wil_dbg_txrx(wil, "%s(%d)\n", __func__, ringid);

        while (!wil_vring_is_empty(vring)) {
                volatile struct vring_tx_desc *_d =
                                              &vring->va[vring->swtail].tx;
                struct vring_tx_desc dd, *d = &dd;
                dma_addr_t pa;
                struct sk_buff *skb;
                u16 dmalen;

                *d = *_d;

                if (!(d->dma.status & TX_DMA_STATUS_DU))
                        break;

                dmalen = le16_to_cpu(d->dma.length);
                trace_wil6210_tx_done(ringid, vring->swtail, dmalen,
                                      d->dma.error);
                wil_dbg_txrx(wil,
                             "Tx[%3d] : %d bytes, status 0x%02x err 0x%02x\n",
                             vring->swtail, dmalen, d->dma.status,
                             d->dma.error);
                wil_hex_dump_txrx("TxC ", DUMP_PREFIX_NONE, 32, 4,
                                  (const void *)d, sizeof(*d), false);

                pa = wil_desc_addr(&d->dma.addr);
                skb = vring->ctx[vring->swtail];
                if (skb) {
                        if (d->dma.error == 0) {
                                ndev->stats.tx_packets++;
                                ndev->stats.tx_bytes += skb->len;
                        } else {
                                ndev->stats.tx_errors++;
                        }

                        dma_unmap_single(dev, pa, dmalen, DMA_TO_DEVICE);
                        dev_kfree_skb_any(skb);
                        vring->ctx[vring->swtail] = NULL;
                } else {
                        dma_unmap_page(dev, pa, dmalen, DMA_TO_DEVICE);
                }
                d->dma.addr.addr_low = 0;
                d->dma.addr.addr_high = 0;
                d->dma.length = 0;
                d->dma.status = TX_DMA_STATUS_DU;
                vring->swtail = wil_vring_next_tail(vring);
                done++;
        }
        if (wil_vring_avail_tx(vring) > vring->size/4)
                netif_tx_wake_all_queues(wil_to_ndev(wil));

        return done;
}