/****************************************************************************
 * Driver for Solarflare network controllers and boards
 * Copyright 2005-2006 Fen Systems Ltd.
 * Copyright 2005-2015 Solarflare Communications Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation, incorporated herein by reference.
 */

#include <linux/pci.h>
#include <linux/tcp.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <linux/ipv6.h>
#include <linux/slab.h>
#include <net/ipv6.h>
#include <linux/if_ether.h>
#include <linux/highmem.h>
#include <linux/moduleparam.h>
#include <linux/cache.h>
#include "net_driver.h"
#include "efx.h"
#include "io.h"
#include "nic.h"
#include "tx.h"
#include "workarounds.h"
#include "ef10_regs.h"

/* Efx legacy TCP segmentation acceleration.
 *
 * Utilises firmware support to go faster than GSO (but not as fast as TSOv2).
 *
 * Requires TX checksum offload support.
 */

#define PTR_DIFF(p1, p2)  ((u8 *)(p1) - (u8 *)(p2))

/**
 * struct tso_state - TSO state for an SKB
 * @out_len: Remaining length in current segment
 * @seqnum: Current sequence number
 * @ipv4_id: Current IPv4 ID, host endian
 * @packet_space: Remaining space in current packet
 * @dma_addr: DMA address of current position
 * @in_len: Remaining length in current SKB fragment
 * @unmap_len: Length of SKB fragment
 * @unmap_addr: DMA address of SKB fragment
 * @protocol: Network protocol (after any VLAN header)
 * @ip_off: Offset of IP header
 * @tcp_off: Offset of TCP header
 * @header_len: Number of bytes of header
 * @ip_base_len: IPv4 tot_len or IPv6 payload_len, before TCP payload
 * @header_dma_addr: Header DMA address
 * @header_unmap_len: Header DMA mapped length
 *
 * The state used during segmentation.  It is put into this data structure
 * just to make it easy to pass into inline functions.
 */
struct tso_state {
        /* Output position */
        unsigned int out_len;
        unsigned int seqnum;
        u16 ipv4_id;
        unsigned int packet_space;

        /* Input position */
        dma_addr_t dma_addr;
        unsigned int in_len;
        unsigned int unmap_len;
        dma_addr_t unmap_addr;

        __be16 protocol;
        unsigned int ip_off;
        unsigned int tcp_off;
        unsigned int header_len;
        unsigned int ip_base_len;
        dma_addr_t header_dma_addr;
        unsigned int header_unmap_len;
};

static inline void prefetch_ptr(struct efx_tx_queue *tx_queue)
{
        unsigned int insert_ptr = efx_tx_queue_get_insert_index(tx_queue);
        char *ptr;

        ptr = (char *) (tx_queue->buffer + insert_ptr);
        prefetch(ptr);
        prefetch(ptr + 0x80);

        ptr = (char *) (((efx_qword_t *)tx_queue->txd.buf.addr) + insert_ptr);
        prefetch(ptr);
        prefetch(ptr + 0x80);
}

/**
 * efx_tx_queue_insert - push descriptors onto the TX queue
 * @tx_queue:           Efx TX queue
 * @dma_addr:           DMA address of fragment
 * @len:                Length of fragment
 * @final_buffer:       The final buffer inserted into the queue
 *
 * Push descriptors onto the TX queue.
 */
static void efx_tx_queue_insert(struct efx_tx_queue *tx_queue,
                                dma_addr_t dma_addr, unsigned int len,
                                struct efx_tx_buffer **final_buffer)
{
        struct efx_tx_buffer *buffer;
        unsigned int dma_len;

        EFX_WARN_ON_ONCE_PARANOID(len <= 0);

        while (1) {
                buffer = efx_tx_queue_get_insert_buffer(tx_queue);
                ++tx_queue->insert_count;

                EFX_WARN_ON_ONCE_PARANOID(tx_queue->insert_count -
                                          tx_queue->read_count >=
                                          tx_queue->efx->txq_entries);

                buffer->dma_addr = dma_addr;

                dma_len = tx_queue->efx->type->tx_limit_len(tx_queue,
                                dma_addr, len);

                /* If there's space for everything this is our last buffer. */
                if (dma_len >= len)
                        break;

                buffer->len = dma_len;
                buffer->flags = EFX_TX_BUF_CONT;
                dma_addr += dma_len;
                len -= dma_len;
        }

        EFX_WARN_ON_ONCE_PARANOID(!len);
        buffer->len = len;
        *final_buffer = buffer;
}

/*
 * Verify that our various assumptions about sk_buffs and the conditions
 * under which TSO will be attempted hold true.  Return the protocol number.
 */
static __be16 efx_tso_check_protocol(struct sk_buff *skb)
{
        __be16 protocol = skb->protocol;

        EFX_WARN_ON_ONCE_PARANOID(((struct ethhdr *)skb->data)->h_proto !=
                                  protocol);
        if (protocol == htons(ETH_P_8021Q)) {
                struct vlan_ethhdr *veh = (struct vlan_ethhdr *)skb->data;

                protocol = veh->h_vlan_encapsulated_proto;
        }

        if (protocol == htons(ETH_P_IP)) {
                EFX_WARN_ON_ONCE_PARANOID(ip_hdr(skb)->protocol != IPPROTO_TCP);
        } else {
                EFX_WARN_ON_ONCE_PARANOID(protocol != htons(ETH_P_IPV6));
                EFX_WARN_ON_ONCE_PARANOID(ipv6_hdr(skb)->nexthdr != NEXTHDR_TCP);
        }
        EFX_WARN_ON_ONCE_PARANOID((PTR_DIFF(tcp_hdr(skb), skb->data) +
                                   (tcp_hdr(skb)->doff << 2u)) >
                                  skb_headlen(skb));

        return protocol;
}

/* Parse the SKB header and initialise state. */
static int tso_start(struct tso_state *st, struct efx_nic *efx,
                     struct efx_tx_queue *tx_queue,
                     const struct sk_buff *skb)
{
        struct device *dma_dev = &efx->pci_dev->dev;
        unsigned int header_len, in_len;
        dma_addr_t dma_addr;

        st->ip_off = skb_network_header(skb) - skb->data;
        st->tcp_off = skb_transport_header(skb) - skb->data;
        header_len = st->tcp_off + (tcp_hdr(skb)->doff << 2u);
        in_len = skb_headlen(skb) - header_len;
        st->header_len = header_len;
        st->in_len = in_len;
        if (st->protocol == htons(ETH_P_IP)) {
                st->ip_base_len = st->header_len - st->ip_off;
                st->ipv4_id = ntohs(ip_hdr(skb)->id);
        } else {
                st->ip_base_len = st->header_len - st->tcp_off;
                st->ipv4_id = 0;
        }
        st->seqnum = ntohl(tcp_hdr(skb)->seq);

        EFX_WARN_ON_ONCE_PARANOID(tcp_hdr(skb)->urg);
        EFX_WARN_ON_ONCE_PARANOID(tcp_hdr(skb)->syn);
        EFX_WARN_ON_ONCE_PARANOID(tcp_hdr(skb)->rst);

        st->out_len = skb->len - header_len;

        dma_addr = dma_map_single(dma_dev, skb->data,
                                  skb_headlen(skb), DMA_TO_DEVICE);
        st->header_dma_addr = dma_addr;
        st->header_unmap_len = skb_headlen(skb);
        st->dma_addr = dma_addr + header_len;
        st->unmap_len = 0;

        return unlikely(dma_mapping_error(dma_dev, dma_addr)) ? -ENOMEM : 0;
}

static int tso_get_fragment(struct tso_state *st, struct efx_nic *efx,
                            skb_frag_t *frag)
{
        st->unmap_addr = skb_frag_dma_map(&efx->pci_dev->dev, frag, 0,
                                          skb_frag_size(frag), DMA_TO_DEVICE);
        if (likely(!dma_mapping_error(&efx->pci_dev->dev, st->unmap_addr))) {
                st->unmap_len = skb_frag_size(frag);
                st->in_len = skb_frag_size(frag);
                st->dma_addr = st->unmap_addr;
                return 0;
        }
        return -ENOMEM;
}


/**
 * tso_fill_packet_with_fragment - form descriptors for the current fragment
 * @tx_queue:           Efx TX queue
 * @skb:                Socket buffer
 * @st:                 TSO state
 *
 * Form descriptors for the current fragment, until we reach the end
 * of fragment or end-of-packet.
 */
static void tso_fill_packet_with_fragment(struct efx_tx_queue *tx_queue,
                                          const struct sk_buff *skb,
                                          struct tso_state *st)
{
        struct efx_tx_buffer *buffer;
        int n;

        if (st->in_len == 0)
                return;
        if (st->packet_space == 0)
                return;

        EFX_WARN_ON_ONCE_PARANOID(st->in_len <= 0);
        EFX_WARN_ON_ONCE_PARANOID(st->packet_space <= 0);

        n = min(st->in_len, st->packet_space);

        st->packet_space -= n;
        st->out_len -= n;
        st->in_len -= n;

        efx_tx_queue_insert(tx_queue, st->dma_addr, n, &buffer);

        if (st->out_len == 0) {
                /* Transfer ownership of the skb */
                buffer->skb = skb;
                buffer->flags = EFX_TX_BUF_SKB;
        } else if (st->packet_space != 0) {
                buffer->flags = EFX_TX_BUF_CONT;
        }

        if (st->in_len == 0) {
                /* Transfer ownership of the DMA mapping */
                buffer->unmap_len = st->unmap_len;
                buffer->dma_offset = buffer->unmap_len - buffer->len;
                st->unmap_len = 0;
        }

        st->dma_addr += n;
}


#define TCP_FLAGS_OFFSET 13

/**
 * tso_start_new_packet - generate a new header and prepare for the new packet
 * @tx_queue:           Efx TX queue
 * @skb:                Socket buffer
 * @st:                 TSO state
 *
 * Generate a new header and prepare for the new packet.  Return 0 on
 * success, or -%ENOMEM if failed to alloc header, or other negative error.
 */
static int tso_start_new_packet(struct efx_tx_queue *tx_queue,
                                const struct sk_buff *skb,
                                struct tso_state *st)
{
        struct efx_tx_buffer *buffer =
                efx_tx_queue_get_insert_buffer(tx_queue);
        bool is_last = st->out_len <= skb_shinfo(skb)->gso_size;
        u8 tcp_flags_mask, tcp_flags;

        if (!is_last) {
                st->packet_space = skb_shinfo(skb)->gso_size;
                tcp_flags_mask = 0x09; /* mask out FIN and PSH */
        } else {
                st->packet_space = st->out_len;
                tcp_flags_mask = 0x00;
        }

        if (WARN_ON(!st->header_unmap_len))
                return -EINVAL;
        /* Send the original headers with a TSO option descriptor
         * in front
         */
        tcp_flags = ((u8 *)tcp_hdr(skb))[TCP_FLAGS_OFFSET] & ~tcp_flags_mask;

        buffer->flags = EFX_TX_BUF_OPTION;
        buffer->len = 0;
        buffer->unmap_len = 0;
        EFX_POPULATE_QWORD_5(buffer->option,
                             ESF_DZ_TX_DESC_IS_OPT, 1,
                             ESF_DZ_TX_OPTION_TYPE,
                             ESE_DZ_TX_OPTION_DESC_TSO,
                             ESF_DZ_TX_TSO_TCP_FLAGS, tcp_flags,
                             ESF_DZ_TX_TSO_IP_ID, st->ipv4_id,
                             ESF_DZ_TX_TSO_TCP_SEQNO, st->seqnum);
        ++tx_queue->insert_count;

        /* We mapped the headers in tso_start().  Unmap them
         * when the last segment is completed.
         */
        buffer = efx_tx_queue_get_insert_buffer(tx_queue);
        buffer->dma_addr = st->header_dma_addr;
        buffer->len = st->header_len;
        if (is_last) {
                buffer->flags = EFX_TX_BUF_CONT | EFX_TX_BUF_MAP_SINGLE;
                buffer->unmap_len = st->header_unmap_len;
                buffer->dma_offset = 0;
                /* Ensure we only unmap them once in case of a
                 * later DMA mapping error and rollback
                 */
                st->header_unmap_len = 0;
        } else {
                buffer->flags = EFX_TX_BUF_CONT;
                buffer->unmap_len = 0;
        }
        ++tx_queue->insert_count;

        st->seqnum += skb_shinfo(skb)->gso_size;

        /* Linux leaves suitable gaps in the IP ID space for us to fill. */
        ++st->ipv4_id;

        return 0;
}

/**
 * efx_enqueue_skb_tso - segment and transmit a TSO socket buffer
 * @tx_queue:           Efx TX queue
 * @skb:                Socket buffer
 * @data_mapped:        Did we map the data? Always set to true
 *                      by this on success.
 *
 * Context: You must hold netif_tx_lock() to call this function.
 *
 * Add socket buffer @skb to @tx_queue, doing TSO or return != 0 if
 * @skb was not enqueued.  @skb is consumed unless return value is
 * %EINVAL.
 */
int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue,
                        struct sk_buff *skb,
                        bool *data_mapped)
{
        struct efx_nic *efx = tx_queue->efx;
        int frag_i, rc;
        struct tso_state state;

        if (tx_queue->tso_version != 1)
                return -EINVAL;

        prefetch(skb->data);

        /* Find the packet protocol and sanity-check it */
        state.protocol = efx_tso_check_protocol(skb);

        EFX_WARN_ON_ONCE_PARANOID(tx_queue->write_count != tx_queue->insert_count);

        rc = tso_start(&state, efx, tx_queue, skb);
        if (rc)
                goto fail;

        if (likely(state.in_len == 0)) {
                /* Grab the first payload fragment. */
                EFX_WARN_ON_ONCE_PARANOID(skb_shinfo(skb)->nr_frags < 1);
                frag_i = 0;
                rc = tso_get_fragment(&state, efx,
                                      skb_shinfo(skb)->frags + frag_i);
                if (rc)
                        goto fail;
        } else {
                /* Payload starts in the header area. */
                frag_i = -1;
        }

        rc = tso_start_new_packet(tx_queue, skb, &state);
        if (rc)
                goto fail;

        prefetch_ptr(tx_queue);

        while (1) {
                tso_fill_packet_with_fragment(tx_queue, skb, &state);

                /* Move onto the next fragment? */
                if (state.in_len == 0) {
                        if (++frag_i >= skb_shinfo(skb)->nr_frags)
                                /* End of payload reached. */
                                break;
                        rc = tso_get_fragment(&state, efx,
                                              skb_shinfo(skb)->frags + frag_i);
                        if (rc)
                                goto fail;
                }

                /* Start at new packet? */
                if (state.packet_space == 0) {
                        rc = tso_start_new_packet(tx_queue, skb, &state);
                        if (rc)
                                goto fail;
                }
        }

        *data_mapped = true;

        return 0;

fail:
        if (rc == -ENOMEM)
                netif_err(efx, tx_err, efx->net_dev,
                          "Out of memory for TSO headers, or DMA mapping error\n");
        else
                netif_err(efx, tx_err, efx->net_dev, "TSO failed, rc = %d\n", rc);

        /* Free the DMA mapping we were in the process of writing out */
        if (state.unmap_len) {
                dma_unmap_page(&efx->pci_dev->dev, state.unmap_addr,
                               state.unmap_len, DMA_TO_DEVICE);
        }

        /* Free the header DMA mapping */
        if (state.header_unmap_len)
                dma_unmap_single(&efx->pci_dev->dev, state.header_dma_addr,
                                 state.header_unmap_len, DMA_TO_DEVICE);

        return rc;
}