tilepro.c

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/*
 * Copyright 2011 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/sched.h>
#include <linux/kernel.h>      /* printk() */
#include <linux/slab.h>        /* kmalloc() */
#include <linux/errno.h>       /* error codes */
#include <linux/types.h>       /* size_t */
#include <linux/interrupt.h>
#include <linux/in.h>
#include <linux/netdevice.h>   /* struct device, and other headers */
#include <linux/etherdevice.h> /* eth_type_trans */
#include <linux/skbuff.h>
#include <linux/ioctl.h>
#include <linux/cdev.h>
#include <linux/hugetlb.h>
#include <linux/in6.h>
#include <linux/timer.h>
#include <linux/io.h>
#include <asm/checksum.h>
#include <asm/homecache.h>

#include <hv/drv_xgbe_intf.h>
#include <hv/drv_xgbe_impl.h>
#include <hv/hypervisor.h>
#include <hv/netio_intf.h>

/* For TSO */
#include <linux/ip.h>
#include <linux/tcp.h>


/*
 * First, "tile_net_init_module()" initializes all four "devices" which
 * can be used by linux.
 *
 * Then, "ifconfig DEVICE up" calls "tile_net_open()", which analyzes
 * the network cpus, then uses "tile_net_open_aux()" to initialize
 * LIPP/LEPP, and then uses "tile_net_open_inner()" to register all
 * the tiles, provide buffers to LIPP, allow ingress to start, and
 * turn on hypervisor interrupt handling (and NAPI) on all tiles.
 *
 * If registration fails due to the link being down, then "retry_work"
 * is used to keep calling "tile_net_open_inner()" until it succeeds.
 *
 * If "ifconfig DEVICE down" is called, it uses "tile_net_stop()" to
 * stop egress, drain the LIPP buffers, unregister all the tiles, stop
 * LIPP/LEPP, and wipe the LEPP queue.
 *
 * We start out with the ingress interrupt enabled on each CPU.  When
 * this interrupt fires, we disable it, and call "napi_schedule()".
 * This will cause "tile_net_poll()" to be called, which will pull
 * packets from the netio queue, filtering them out, or passing them
 * to "netif_receive_skb()".  If our budget is exhausted, we will
 * return, knowing we will be called again later.  Otherwise, we
 * reenable the ingress interrupt, and call "napi_complete()".
 *
 * HACK: Since disabling the ingress interrupt is not reliable, we
 * ignore the interrupt if the global "active" flag is false.
 *
 *
 * NOTE: The use of "native_driver" ensures that EPP exists, and that
 * we are using "LIPP" and "LEPP".
 *
 * NOTE: Failing to free completions for an arbitrarily long time
 * (which is defined to be illegal) does in fact cause bizarre
 * problems.  The "egress_timer" helps prevent this from happening.
 */


/* HACK: Allow use of "jumbo" packets. */
/* This should be 1500 if "jumbo" is not set in LIPP. */
/* This should be at most 10226 (10240 - 14) if "jumbo" is set in LIPP. */
/* ISSUE: This has not been thoroughly tested (except at 1500). */
#define TILE_NET_MTU 1500

/* HACK: Define to support GSO. */
/* ISSUE: This may actually hurt performance of the TCP blaster. */
/* #define TILE_NET_GSO */

/* Define this to collapse "duplicate" acks. */
/* #define IGNORE_DUP_ACKS */

/* HACK: Define this to verify incoming packets. */
/* #define TILE_NET_VERIFY_INGRESS */

/* Use 3000 to enable the Linux Traffic Control (QoS) layer, else 0. */
#define TILE_NET_TX_QUEUE_LEN 0

/* Define to dump packets (prints out the whole packet on tx and rx). */
/* #define TILE_NET_DUMP_PACKETS */

/* Define to enable debug spew (all PDEBUG's are enabled). */
/* #define TILE_NET_DEBUG */


/* Define to activate paranoia checks. */
/* #define TILE_NET_PARANOIA */

/* Default transmit lockup timeout period, in jiffies. */
#define TILE_NET_TIMEOUT (5 * HZ)

/* Default retry interval for bringing up the NetIO interface, in jiffies. */
#define TILE_NET_RETRY_INTERVAL (5 * HZ)

/* Number of ports (xgbe0, xgbe1, gbe0, gbe1). */
#define TILE_NET_DEVS 4



/* Paranoia. */
#if NET_IP_ALIGN != LIPP_PACKET_PADDING
#error "NET_IP_ALIGN must match LIPP_PACKET_PADDING."
#endif


/* Debug print. */
#ifdef TILE_NET_DEBUG
#define PDEBUG(fmt, args...) net_printk(fmt, ## args)
#else
#define PDEBUG(fmt, args...)
#endif


MODULE_AUTHOR("Tilera");
MODULE_LICENSE("GPL");


/*
 * Queue of incoming packets for a specific cpu and device.
 *
 * Includes a pointer to the "system" data, and the actual "user" data.
 */
struct tile_netio_queue {
    netio_queue_impl_t *__system_part;
    netio_queue_user_impl_t __user_part;

};


/*
 * Statistics counters for a specific cpu and device.
 */
struct tile_net_stats_t {
    u32 rx_packets;
    u32 rx_bytes;
    u32 tx_packets;
    u32 tx_bytes;
};


/*
 * Info for a specific cpu and device.
 *
 * ISSUE: There is a "dev" pointer in "napi" as well.
 */
struct tile_net_cpu {
    /* The NAPI struct. */
    struct napi_struct napi;
    /* Packet queue. */
    struct tile_netio_queue queue;
    /* Statistics. */
    struct tile_net_stats_t stats;
    /* True iff NAPI is enabled. */
    bool napi_enabled;
    /* True if this tile has successfully registered with the IPP. */
    bool registered;
    /* True if the link was down last time we tried to register. */
    bool link_down;
    /* True if "egress_timer" is scheduled. */
    bool egress_timer_scheduled;
    /* Number of small sk_buffs which must still be provided. */
    unsigned int num_needed_small_buffers;
    /* Number of large sk_buffs which must still be provided. */
    unsigned int num_needed_large_buffers;
    /* A timer for handling egress completions. */
    struct timer_list egress_timer;
};


/*
 * Info for a specific device.
 */
struct tile_net_priv {
    /* Our network device. */
    struct net_device *dev;
    /* Pages making up the egress queue. */
    struct page *eq_pages;
    /* Address of the actual egress queue. */
    lepp_queue_t *eq;
    /* Protects "eq". */
    spinlock_t eq_lock;
    /* The hypervisor handle for this interface. */
    int hv_devhdl;
    /* The intr bit mask that IDs this device. */
    u32 intr_id;
    /* True iff "tile_net_open_aux()" has succeeded. */
    bool partly_opened;
    /* True iff the device is "active". */
    bool active;
    /* Effective network cpus. */
    struct cpumask network_cpus_map;
    /* Number of network cpus. */
    int network_cpus_count;
    /* Credits per network cpu. */
    int network_cpus_credits;
    /* Network stats. */
    struct net_device_stats stats;
    /* For NetIO bringup retries. */
    struct delayed_work retry_work;
    /* Quick access to per cpu data. */
    struct tile_net_cpu *cpu[NR_CPUS];
};

/* Log2 of the number of small pages needed for the egress queue. */
#define EQ_ORDER  get_order(sizeof(lepp_queue_t))
/* Size of the egress queue's pages. */
#define EQ_SIZE   (1 << (PAGE_SHIFT + EQ_ORDER))

/*
 * The actual devices (xgbe0, xgbe1, gbe0, gbe1).
 */
static struct net_device *tile_net_devs[TILE_NET_DEVS];

/*
 * The "tile_net_cpu" structures for each device.
 */
static DEFINE_PER_CPU(struct tile_net_cpu, hv_xgbe0);
static DEFINE_PER_CPU(struct tile_net_cpu, hv_xgbe1);
static DEFINE_PER_CPU(struct tile_net_cpu, hv_gbe0);
static DEFINE_PER_CPU(struct tile_net_cpu, hv_gbe1);


/*
 * True if "network_cpus" was specified.
 */
static bool network_cpus_used;

/*
 * The actual cpus in "network_cpus".
 */
static struct cpumask network_cpus_map;



#ifdef TILE_NET_DEBUG
/*
 * printk with extra stuff.
 *
 * We print the CPU we're running in brackets.
 */
static void net_printk(char *fmt, ...)
{
    int i;
    int len;
    va_list args;
    static char buf[256];

    len = sprintf(buf, "tile_net[%2.2d]: ", smp_processor_id());
    va_start(args, fmt);
    i = vscnprintf(buf + len, sizeof(buf) - len - 1, fmt, args);
    va_end(args);
    buf[255] = '\0';
    pr_notice(buf);
}
#endif


#ifdef TILE_NET_DUMP_PACKETS
/*
 * Dump a packet.
 */
static void dump_packet(unsigned char *data, unsigned long length, char *s)
{
    int my_cpu = smp_processor_id();

    unsigned long i;
    char buf[128];

    static unsigned int count;

    pr_info("dump_packet(data %p, length 0x%lx s %s count 0x%x)\n",
           data, length, s, count++);

    pr_info("\n");

    for (i = 0; i < length; i++) {
        if ((i & 0xf) == 0)
            sprintf(buf, "[%02d] %8.8lx:", my_cpu, i);
        sprintf(buf + strlen(buf), " %2.2x", data[i]);
        if ((i & 0xf) == 0xf || i == length - 1) {
            strcat(buf, "\n");
            pr_info("%s", buf);
        }
    }
}
#endif


/*
 * Provide support for the __netio_fastio1() swint
 * (see <hv/drv_xgbe_intf.h> for how it is used).
 *
 * The fastio swint2 call may clobber all the caller-saved registers.
 * It rarely clobbers memory, but we allow for the possibility in
 * the signature just to be on the safe side.
 *
 * Also, gcc doesn't seem to allow an input operand to be
 * clobbered, so we fake it with dummy outputs.
 *
 * This function can't be static because of the way it is declared
 * in the netio header.
 */
inline int __netio_fastio1(u32 fastio_index, u32 arg0)
{
    long result, clobber_r1, clobber_r10;
    asm volatile("swint2"
             : "=R00" (result),
               "=R01" (clobber_r1), "=R10" (clobber_r10)
             : "R10" (fastio_index), "R01" (arg0)
             : "memory", "r2", "r3", "r4",
               "r5", "r6", "r7", "r8", "r9",
               "r11", "r12", "r13", "r14",
               "r15", "r16", "r17", "r18", "r19",
               "r20", "r21", "r22", "r23", "r24",
               "r25", "r26", "r27", "r28", "r29");
    return result;
}


static void tile_net_return_credit(struct tile_net_cpu *info)
{
    struct tile_netio_queue *queue = &info->queue;
    netio_queue_user_impl_t *qup = &queue->__user_part;

    /* Return four credits after every fourth packet. */
    if (--qup->__receive_credit_remaining == 0) {
        u32 interval = qup->__receive_credit_interval;
        qup->__receive_credit_remaining = interval;
        __netio_fastio_return_credits(qup->__fastio_index, interval);
    }
}



/*
 * Provide a linux buffer to LIPP.
 */
static void tile_net_provide_linux_buffer(struct tile_net_cpu *info,
                      void *va, bool small)
{
    struct tile_netio_queue *queue = &info->queue;

    /* Convert "va" and "small" to "linux_buffer_t". */
    unsigned int buffer = ((unsigned int)(__pa(va) >> 7) << 1) + small;

    __netio_fastio_free_buffer(queue->__user_part.__fastio_index, buffer);
}


/*
 * Provide a linux buffer for LIPP.
 *
 * Note that the ACTUAL allocation for each buffer is a "struct sk_buff",
 * plus a chunk of memory that includes not only the requested bytes, but
 * also NET_SKB_PAD bytes of initial padding, and a "struct skb_shared_info".
 *
 * Note that "struct skb_shared_info" is 88 bytes with 64K pages and
 * 268 bytes with 4K pages (since the frags[] array needs 18 entries).
 *
 * Without jumbo packets, the maximum packet size will be 1536 bytes,
 * and we use 2 bytes (NET_IP_ALIGN) of padding.  ISSUE: If we told
 * the hardware to clip at 1518 bytes instead of 1536 bytes, then we
 * could save an entire cache line, but in practice, we don't need it.
 *
 * Since CPAs are 38 bits, and we can only encode the high 31 bits in
 * a "linux_buffer_t", the low 7 bits must be zero, and thus, we must
 * align the actual "va" mod 128.
 *
 * We assume that the underlying "head" will be aligned mod 64.  Note
 * that in practice, we have seen "head" NOT aligned mod 128 even when
 * using 2048 byte allocations, which is surprising.
 *
 * If "head" WAS always aligned mod 128, we could change LIPP to
 * assume that the low SIX bits are zero, and the 7th bit is one, that
 * is, align the actual "va" mod 128 plus 64, which would be "free".
 *
 * For now, the actual "head" pointer points at NET_SKB_PAD bytes of
 * padding, plus 28 or 92 bytes of extra padding, plus the sk_buff
 * pointer, plus the NET_IP_ALIGN padding, plus 126 or 1536 bytes for
 * the actual packet, plus 62 bytes of empty padding, plus some
 * padding and the "struct skb_shared_info".
 *
 * With 64K pages, a large buffer thus needs 32+92+4+2+1536+62+88
 * bytes, or 1816 bytes, which fits comfortably into 2048 bytes.
 *
 * With 64K pages, a small buffer thus needs 32+92+4+2+126+88
 * bytes, or 344 bytes, which means we are wasting 64+ bytes, and
 * could presumably increase the size of small buffers.
 *
 * With 4K pages, a large buffer thus needs 32+92+4+2+1536+62+268
 * bytes, or 1996 bytes, which fits comfortably into 2048 bytes.
 *
 * With 4K pages, a small buffer thus needs 32+92+4+2+126+268
 * bytes, or 524 bytes, which is annoyingly wasteful.
 *
 * Maybe we should increase LIPP_SMALL_PACKET_SIZE to 192?
 *
 * ISSUE: Maybe we should increase "NET_SKB_PAD" to 64?
 */
static bool tile_net_provide_needed_buffer(struct tile_net_cpu *info,
                       bool small)
{
#if TILE_NET_MTU <= 1536
    /* Without "jumbo", 2 + 1536 should be sufficient. */
    unsigned int large_size = NET_IP_ALIGN + 1536;
#else
    /* ISSUE: This has not been tested. */
    unsigned int large_size = NET_IP_ALIGN + TILE_NET_MTU + 100;
#endif

    /* Avoid "false sharing" with last cache line. */
    /* ISSUE: This is already done by "netdev_alloc_skb()". */
    unsigned int len =
         (((small ? LIPP_SMALL_PACKET_SIZE : large_size) +
           CHIP_L2_LINE_SIZE() - 1) & -CHIP_L2_LINE_SIZE());

    unsigned int padding = 128 - NET_SKB_PAD;
    unsigned int align;

    struct sk_buff *skb;
    void *va;

    struct sk_buff **skb_ptr;

    /* Request 96 extra bytes for alignment purposes. */
    skb = netdev_alloc_skb(info->napi.dev, len + padding);
    if (skb == NULL)
        return false;

    /* Skip 32 or 96 bytes to align "data" mod 128. */
    align = -(long)skb->data & (128 - 1);
    BUG_ON(align > padding);
    skb_reserve(skb, align);

    /* This address is given to IPP. */
    va = skb->data;

    /* Buffers must not span a huge page. */
    BUG_ON(((((long)va & ~HPAGE_MASK) + len) & HPAGE_MASK) != 0);

#ifdef TILE_NET_PARANOIA
#if CHIP_HAS_CBOX_HOME_MAP()
    if (hash_default) {
        HV_PTE pte = *virt_to_pte(current->mm, (unsigned long)va);
        if (hv_pte_get_mode(pte) != HV_PTE_MODE_CACHE_HASH_L3)
            panic("Non-HFH ingress buffer! VA=%p Mode=%d PTE=%llx",
                  va, hv_pte_get_mode(pte), hv_pte_val(pte));
    }
#endif
#endif

    /* Invalidate the packet buffer. */
    if (!hash_default)
        __inv_buffer(va, len);

    /* Skip two bytes to satisfy LIPP assumptions. */
    /* Note that this aligns IP on a 16 byte boundary. */
    /* ISSUE: Do this when the packet arrives? */
    skb_reserve(skb, NET_IP_ALIGN);

    /* Save a back-pointer to 'skb'. */
    skb_ptr = va - sizeof(*skb_ptr);
    *skb_ptr = skb;

    /* Make sure "skb_ptr" has been flushed. */
    __insn_mf();

    /* Provide the new buffer. */
    tile_net_provide_linux_buffer(info, va, small);

    return true;
}


/*
 * Provide linux buffers for LIPP.
 */
static void tile_net_provide_needed_buffers(struct tile_net_cpu *info)
{
    while (info->num_needed_small_buffers != 0) {
        if (!tile_net_provide_needed_buffer(info, true))
            goto oops;
        info->num_needed_small_buffers--;
    }

    while (info->num_needed_large_buffers != 0) {
        if (!tile_net_provide_needed_buffer(info, false))
            goto oops;
        info->num_needed_large_buffers--;
    }

    return;

oops:

    /* Add a description to the page allocation failure dump. */
    pr_notice("Could not provide a linux buffer to LIPP.\n");
}


/*
 * Grab some LEPP completions, and store them in "comps", of size
 * "comps_size", and return the number of completions which were
 * stored, so the caller can free them.
 */
static unsigned int tile_net_lepp_grab_comps(lepp_queue_t *eq,
                         struct sk_buff *comps[],
                         unsigned int comps_size,
                         unsigned int min_size)
{
    unsigned int n = 0;

    unsigned int comp_head = eq->comp_head;
    unsigned int comp_busy = eq->comp_busy;

    while (comp_head != comp_busy && n < comps_size) {
        comps[n++] = eq->comps[comp_head];
        LEPP_QINC(comp_head);
    }

    if (n < min_size)
        return 0;

    eq->comp_head = comp_head;

    return n;
}


/*
 * Free some comps, and return true iff there are still some pending.
 */
static bool tile_net_lepp_free_comps(struct net_device *dev, bool all)
{
    struct tile_net_priv *priv = netdev_priv(dev);

    lepp_queue_t *eq = priv->eq;

    struct sk_buff *olds[64];
    unsigned int wanted = 64;
    unsigned int i, n;
    bool pending;

    spin_lock(&priv->eq_lock);

    if (all)
        eq->comp_busy = eq->comp_tail;

    n = tile_net_lepp_grab_comps(eq, olds, wanted, 0);

    pending = (eq->comp_head != eq->comp_tail);

    spin_unlock(&priv->eq_lock);

    for (i = 0; i < n; i++)
        kfree_skb(olds[i]);

    return pending;
}


/*
 * Make sure the egress timer is scheduled.
 *
 * Note that we use "schedule if not scheduled" logic instead of the more
 * obvious "reschedule" logic, because "reschedule" is fairly expensive.
 */
static void tile_net_schedule_egress_timer(struct tile_net_cpu *info)
{
    if (!info->egress_timer_scheduled) {
        mod_timer_pinned(&info->egress_timer, jiffies + 1);
        info->egress_timer_scheduled = true;
    }
}


/*
 * The "function" for "info->egress_timer".
 *
 * This timer will reschedule itself as long as there are any pending
 * completions expected (on behalf of any tile).
 *
 * ISSUE: Realistically, will the timer ever stop scheduling itself?
 *
 * ISSUE: This timer is almost never actually needed, so just use a global
 * timer that can run on any tile.
 *
 * ISSUE: Maybe instead track number of expected completions, and free
 * only that many, resetting to zero if "pending" is ever false.
 */
static void tile_net_handle_egress_timer(unsigned long arg)
{
    struct tile_net_cpu *info = (struct tile_net_cpu *)arg;
    struct net_device *dev = info->napi.dev;

    /* The timer is no longer scheduled. */
    info->egress_timer_scheduled = false;

    /* Free comps, and reschedule timer if more are pending. */
    if (tile_net_lepp_free_comps(dev, false))
        tile_net_schedule_egress_timer(info);
}


#ifdef IGNORE_DUP_ACKS

/*
 * Help detect "duplicate" ACKs.  These are sequential packets (for a
 * given flow) which are exactly 66 bytes long, sharing everything but
 * ID=2@0x12, Hsum=2@0x18, Ack=4@0x2a, WinSize=2@0x30, Csum=2@0x32,
 * Tstamps=10@0x38.  The ID's are +1, the Hsum's are -1, the Ack's are
 * +N, and the Tstamps are usually identical.
 *
 * NOTE: Apparently truly duplicate acks (with identical "ack" values),
 * should not be collapsed, as they are used for some kind of flow control.
 */
static bool is_dup_ack(char *s1, char *s2, unsigned int len)
{
    int i;

    unsigned long long ignorable = 0;

    /* Identification. */
    ignorable |= (1ULL << 0x12);
    ignorable |= (1ULL << 0x13);

    /* Header checksum. */
    ignorable |= (1ULL << 0x18);
    ignorable |= (1ULL << 0x19);

    /* ACK. */
    ignorable |= (1ULL << 0x2a);
    ignorable |= (1ULL << 0x2b);
    ignorable |= (1ULL << 0x2c);
    ignorable |= (1ULL << 0x2d);

    /* WinSize. */
    ignorable |= (1ULL << 0x30);
    ignorable |= (1ULL << 0x31);

    /* Checksum. */
    ignorable |= (1ULL << 0x32);
    ignorable |= (1ULL << 0x33);

    for (i = 0; i < len; i++, ignorable >>= 1) {

        if ((ignorable & 1) || (s1[i] == s2[i]))
            continue;

#ifdef TILE_NET_DEBUG
        /* HACK: Mention non-timestamp diffs. */
        if (i < 0x38 && i != 0x2f &&
            net_ratelimit())
            pr_info("Diff at 0x%x\n", i);
#endif

        return false;
    }

#ifdef TILE_NET_NO_SUPPRESS_DUP_ACKS
    /* HACK: Do not suppress truly duplicate ACKs. */
    /* ISSUE: Is this actually necessary or helpful? */
    if (s1[0x2a] == s2[0x2a] &&
        s1[0x2b] == s2[0x2b] &&
        s1[0x2c] == s2[0x2c] &&
        s1[0x2d] == s2[0x2d]) {
        return false;
    }
#endif

    return true;
}

#endif



static void tile_net_discard_aux(struct tile_net_cpu *info, int index)
{
    struct tile_netio_queue *queue = &info->queue;
    netio_queue_impl_t *qsp = queue->__system_part;
    netio_queue_user_impl_t *qup = &queue->__user_part;

    int index2_aux = index + sizeof(netio_pkt_t);
    int index2 =
        ((index2_aux ==
          qsp->__packet_receive_queue.__last_packet_plus_one) ?
         0 : index2_aux);

    netio_pkt_t *pkt = (netio_pkt_t *)((unsigned long) &qsp[1] + index);

    /* Extract the "linux_buffer_t". */
    unsigned int buffer = pkt->__packet.word;

    /* Convert "linux_buffer_t" to "va". */
    void *va = __va((phys_addr_t)(buffer >> 1) << 7);

    /* Acquire the associated "skb". */
    struct sk_buff **skb_ptr = va - sizeof(*skb_ptr);
    struct sk_buff *skb = *skb_ptr;

    kfree_skb(skb);

    /* Consume this packet. */
    qup->__packet_receive_read = index2;
}


/*
 * Like "tile_net_poll()", but just discard packets.
 */
static void tile_net_discard_packets(struct net_device *dev)
{
    struct tile_net_priv *priv = netdev_priv(dev);
    int my_cpu = smp_processor_id();
    struct tile_net_cpu *info = priv->cpu[my_cpu];
    struct tile_netio_queue *queue = &info->queue;
    netio_queue_impl_t *qsp = queue->__system_part;
    netio_queue_user_impl_t *qup = &queue->__user_part;

    while (qup->__packet_receive_read !=
           qsp->__packet_receive_queue.__packet_write) {
        int index = qup->__packet_receive_read;
        tile_net_discard_aux(info, index);
    }
}


/*
 * Handle the next packet.  Return true if "processed", false if "filtered".
 */
static bool tile_net_poll_aux(struct tile_net_cpu *info, int index)
{
    struct net_device *dev = info->napi.dev;

    struct tile_netio_queue *queue = &info->queue;
    netio_queue_impl_t *qsp = queue->__system_part;
    netio_queue_user_impl_t *qup = &queue->__user_part;
    struct tile_net_stats_t *stats = &info->stats;

    int filter;

    int index2_aux = index + sizeof(netio_pkt_t);
    int index2 =
        ((index2_aux ==
          qsp->__packet_receive_queue.__last_packet_plus_one) ?
         0 : index2_aux);

    netio_pkt_t *pkt = (netio_pkt_t *)((unsigned long) &qsp[1] + index);

    netio_pkt_metadata_t *metadata = NETIO_PKT_METADATA(pkt);

    /* Extract the packet size.  FIXME: Shouldn't the second line */
    /* get subtracted?  Mostly moot, since it should be "zero". */
    unsigned long len =
        (NETIO_PKT_CUSTOM_LENGTH(pkt) +
         NET_IP_ALIGN - NETIO_PACKET_PADDING);

    /* Extract the "linux_buffer_t". */
    unsigned int buffer = pkt->__packet.word;

    /* Extract "small" (vs "large"). */
    bool small = ((buffer & 1) != 0);

    /* Convert "linux_buffer_t" to "va". */
    void *va = __va((phys_addr_t)(buffer >> 1) << 7);

    /* Extract the packet data pointer. */
    /* Compare to "NETIO_PKT_CUSTOM_DATA(pkt)". */
    unsigned char *buf = va + NET_IP_ALIGN;

    /* Invalidate the packet buffer. */
    if (!hash_default)
        __inv_buffer(buf, len);

    /* ISSUE: Is this needed? */
    dev->last_rx = jiffies;

#ifdef TILE_NET_DUMP_PACKETS
    dump_packet(buf, len, "rx");
#endif /* TILE_NET_DUMP_PACKETS */

#ifdef TILE_NET_VERIFY_INGRESS
    if (!NETIO_PKT_L4_CSUM_CORRECT_M(metadata, pkt) &&
        NETIO_PKT_L4_CSUM_CALCULATED_M(metadata, pkt)) {
        /* Bug 6624: Includes UDP packets with a "zero" checksum. */
        pr_warning("Bad L4 checksum on %d byte packet.\n", len);
    }
    if (!NETIO_PKT_L3_CSUM_CORRECT_M(metadata, pkt) &&
        NETIO_PKT_L3_CSUM_CALCULATED_M(metadata, pkt)) {
        dump_packet(buf, len, "rx");
        panic("Bad L3 checksum.");
    }
    switch (NETIO_PKT_STATUS_M(metadata, pkt)) {
    case NETIO_PKT_STATUS_OVERSIZE:
        if (len >= 64) {
            dump_packet(buf, len, "rx");
            panic("Unexpected OVERSIZE.");
        }
        break;
    case NETIO_PKT_STATUS_BAD:
        pr_warning("Unexpected BAD %ld byte packet.\n", len);
    }
#endif

    filter = 0;

    /* ISSUE: Filter TCP packets with "bad" checksums? */

    if (!(dev->flags & IFF_UP)) {
        /* Filter packets received before we're up. */
        filter = 1;
    } else if (NETIO_PKT_STATUS_M(metadata, pkt) == NETIO_PKT_STATUS_BAD) {
        /* Filter "truncated" packets. */
        filter = 1;
    } else if (!(dev->flags & IFF_PROMISC)) {
        /* FIXME: Implement HW multicast filter. */
        if (!is_multicast_ether_addr(buf)) {
            /* Filter packets not for our address. */
            const u8 *mine = dev->dev_addr;
            filter = !ether_addr_equal(mine, buf);
        }
    }

    if (filter) {

        /* ISSUE: Update "drop" statistics? */

        tile_net_provide_linux_buffer(info, va, small);

    } else {

        /* Acquire the associated "skb". */
        struct sk_buff **skb_ptr = va - sizeof(*skb_ptr);
        struct sk_buff *skb = *skb_ptr;

        /* Paranoia. */
        if (skb->data != buf)
            panic("Corrupt linux buffer from LIPP! "
                  "VA=%p, skb=%p, skb->data=%p\n",
                  va, skb, skb->data);

        /* Encode the actual packet length. */
        skb_put(skb, len);

        /* NOTE: This call also sets "skb->dev = dev". */
        skb->protocol = eth_type_trans(skb, dev);

        /* Avoid recomputing "good" TCP/UDP checksums. */
        if (NETIO_PKT_L4_CSUM_CORRECT_M(metadata, pkt))
            skb->ip_summed = CHECKSUM_UNNECESSARY;

        netif_receive_skb(skb);

        stats->rx_packets++;
        stats->rx_bytes += len;
    }

    /* ISSUE: It would be nice to defer this until the packet has */
    /* actually been processed. */
    tile_net_return_credit(info);

    /* Consume this packet. */
    qup->__packet_receive_read = index2;

    return !filter;
}


/*
 * Handle some packets for the given device on the current CPU.
 *
 * If "tile_net_stop()" is called on some other tile while this
 * function is running, we will return, hopefully before that
 * other tile asks us to call "napi_disable()".
 *
 * The "rotting packet" race condition occurs if a packet arrives
 * during the extremely narrow window between the queue appearing to
 * be empty, and the ingress interrupt being re-enabled.  This happens
 * a LOT under heavy network load.
 */
static int tile_net_poll(struct napi_struct *napi, int budget)
{
    struct net_device *dev = napi->dev;
    struct tile_net_priv *priv = netdev_priv(dev);
    int my_cpu = smp_processor_id();
    struct tile_net_cpu *info = priv->cpu[my_cpu];
    struct tile_netio_queue *queue = &info->queue;
    netio_queue_impl_t *qsp = queue->__system_part;
    netio_queue_user_impl_t *qup = &queue->__user_part;

    unsigned int work = 0;

    while (priv->active) {
        int index = qup->__packet_receive_read;
        if (index == qsp->__packet_receive_queue.__packet_write)
            break;

        if (tile_net_poll_aux(info, index)) {
            if (++work >= budget)
                goto done;
        }
    }

    napi_complete(&info->napi);

    if (!priv->active)
        goto done;

    /* Re-enable the ingress interrupt. */
    enable_percpu_irq(priv->intr_id, 0);

    /* HACK: Avoid the "rotting packet" problem (see above). */
    if (qup->__packet_receive_read !=
        qsp->__packet_receive_queue.__packet_write) {
        /* ISSUE: Sometimes this returns zero, presumably */
        /* because an interrupt was handled for this tile. */
        (void)napi_reschedule(&info->napi);
    }

done:

    if (priv->active)
        tile_net_provide_needed_buffers(info);

    return work;
}


/*
 * Handle an ingress interrupt for the given device on the current cpu.
 *
 * ISSUE: Sometimes this gets called after "disable_percpu_irq()" has
 * been called!  This is probably due to "pending hypervisor downcalls".
 *
 * ISSUE: Is there any race condition between the "napi_schedule()" here
 * and the "napi_complete()" call above?
 */
static irqreturn_t tile_net_handle_ingress_interrupt(int irq, void *dev_ptr)
{
    struct net_device *dev = (struct net_device *)dev_ptr;
    struct tile_net_priv *priv = netdev_priv(dev);
    int my_cpu = smp_processor_id();
    struct tile_net_cpu *info = priv->cpu[my_cpu];

    /* Disable the ingress interrupt. */
    disable_percpu_irq(priv->intr_id);

    /* Ignore unwanted interrupts. */
    if (!priv->active)
        return IRQ_HANDLED;

    /* ISSUE: Sometimes "info->napi_enabled" is false here. */

    napi_schedule(&info->napi);

    return IRQ_HANDLED;
}


/*
 * One time initialization per interface.
 */
static int tile_net_open_aux(struct net_device *dev)
{
    struct tile_net_priv *priv = netdev_priv(dev);

    int ret;
    int dummy;
    unsigned int epp_lotar;

    /*
     * Find out where EPP memory should be homed.
     */
    ret = hv_dev_pread(priv->hv_devhdl, 0,
               (HV_VirtAddr)&epp_lotar, sizeof(epp_lotar),
               NETIO_EPP_SHM_OFF);
    if (ret < 0) {
        pr_err("could not read epp_shm_queue lotar.\n");
        return -EIO;
    }

    /*
     * Home the page on the EPP.
     */
    {
        int epp_home = hv_lotar_to_cpu(epp_lotar);
        homecache_change_page_home(priv->eq_pages, EQ_ORDER, epp_home);
    }

    /*
     * Register the EPP shared memory queue.
     */
    {
        netio_ipp_address_t ea = {
            .va = 0,
            .pa = __pa(priv->eq),
            .pte = hv_pte(0),
            .size = EQ_SIZE,
        };
        ea.pte = hv_pte_set_lotar(ea.pte, epp_lotar);
        ea.pte = hv_pte_set_mode(ea.pte, HV_PTE_MODE_CACHE_TILE_L3);
        ret = hv_dev_pwrite(priv->hv_devhdl, 0,
                    (HV_VirtAddr)&ea,
                    sizeof(ea),
                    NETIO_EPP_SHM_OFF);
        if (ret < 0)
            return -EIO;
    }

    /*
     * Start LIPP/LEPP.
     */
    if (hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
              sizeof(dummy), NETIO_IPP_START_SHIM_OFF) < 0) {
        pr_warning("Failed to start LIPP/LEPP.\n");
        return -EIO;
    }

    return 0;
}


/*
 * Register with hypervisor on the current CPU.
 *
 * Strangely, this function does important things even if it "fails",
 * which is especially common if the link is not up yet.  Hopefully
 * these things are all "harmless" if done twice!
 */
static void tile_net_register(void *dev_ptr)
{
    struct net_device *dev = (struct net_device *)dev_ptr;
    struct tile_net_priv *priv = netdev_priv(dev);
    int my_cpu = smp_processor_id();
    struct tile_net_cpu *info;

    struct tile_netio_queue *queue;

    /* Only network cpus can receive packets. */
    int queue_id =
        cpumask_test_cpu(my_cpu, &priv->network_cpus_map) ? 0 : 255;

    netio_input_config_t config = {
        .flags = 0,
        .num_receive_packets = priv->network_cpus_credits,
        .queue_id = queue_id
    };

    int ret = 0;
    netio_queue_impl_t *queuep;

    PDEBUG("tile_net_register(queue_id %d)\n", queue_id);

    if (!strcmp(dev->name, "xgbe0"))
        info = &__get_cpu_var(hv_xgbe0);
    else if (!strcmp(dev->name, "xgbe1"))
        info = &__get_cpu_var(hv_xgbe1);
    else if (!strcmp(dev->name, "gbe0"))
        info = &__get_cpu_var(hv_gbe0);
    else if (!strcmp(dev->name, "gbe1"))
        info = &__get_cpu_var(hv_gbe1);
    else
        BUG();

    /* Initialize the egress timer. */
    init_timer(&info->egress_timer);
    info->egress_timer.data = (long)info;
    info->egress_timer.function = tile_net_handle_egress_timer;

    priv->cpu[my_cpu] = info;

    /*
     * Register ourselves with LIPP.  This does a lot of stuff,
     * including invoking the LIPP registration code.
     */
    ret = hv_dev_pwrite(priv->hv_devhdl, 0,
                (HV_VirtAddr)&config,
                sizeof(netio_input_config_t),
                NETIO_IPP_INPUT_REGISTER_OFF);
    PDEBUG("hv_dev_pwrite(NETIO_IPP_INPUT_REGISTER_OFF) returned %d\n",
           ret);
    if (ret < 0) {
        if (ret != NETIO_LINK_DOWN) {
            printk(KERN_DEBUG "hv_dev_pwrite "
                   "NETIO_IPP_INPUT_REGISTER_OFF failure %d\n",
                   ret);
        }
        info->link_down = (ret == NETIO_LINK_DOWN);
        return;
    }

    /*
     * Get the pointer to our queue's system part.
     */

    ret = hv_dev_pread(priv->hv_devhdl, 0,
               (HV_VirtAddr)&queuep,
               sizeof(netio_queue_impl_t *),
               NETIO_IPP_INPUT_REGISTER_OFF);
    PDEBUG("hv_dev_pread(NETIO_IPP_INPUT_REGISTER_OFF) returned %d\n",
           ret);
    PDEBUG("queuep %p\n", queuep);
    if (ret <= 0) {
        /* ISSUE: Shouldn't this be a fatal error? */
        pr_err("hv_dev_pread NETIO_IPP_INPUT_REGISTER_OFF failure\n");
        return;
    }

    queue = &info->queue;

    queue->__system_part = queuep;

    memset(&queue->__user_part, 0, sizeof(netio_queue_user_impl_t));

    /* This is traditionally "config.num_receive_packets / 2". */
    queue->__user_part.__receive_credit_interval = 4;
    queue->__user_part.__receive_credit_remaining =
        queue->__user_part.__receive_credit_interval;

    /*
     * Get a fastio index from the hypervisor.
     * ISSUE: Shouldn't this check the result?
     */
    ret = hv_dev_pread(priv->hv_devhdl, 0,
               (HV_VirtAddr)&queue->__user_part.__fastio_index,
               sizeof(queue->__user_part.__fastio_index),
               NETIO_IPP_GET_FASTIO_OFF);
    PDEBUG("hv_dev_pread(NETIO_IPP_GET_FASTIO_OFF) returned %d\n", ret);

    /* Now we are registered. */
    info->registered = true;
}


/*
 * Deregister with hypervisor on the current CPU.
 *
 * This simply discards all our credits, so no more packets will be
 * delivered to this tile.  There may still be packets in our queue.
 *
 * Also, disable the ingress interrupt.
 */
static void tile_net_deregister(void *dev_ptr)
{
    struct net_device *dev = (struct net_device *)dev_ptr;
    struct tile_net_priv *priv = netdev_priv(dev);
    int my_cpu = smp_processor_id();
    struct tile_net_cpu *info = priv->cpu[my_cpu];

    /* Disable the ingress interrupt. */
    disable_percpu_irq(priv->intr_id);

    /* Do nothing else if not registered. */
    if (info == NULL || !info->registered)
        return;

    {
        struct tile_netio_queue *queue = &info->queue;
        netio_queue_user_impl_t *qup = &queue->__user_part;

        /* Discard all our credits. */
        __netio_fastio_return_credits(qup->__fastio_index, -1);
    }
}


/*
 * Unregister with hypervisor on the current CPU.
 *
 * Also, disable the ingress interrupt.
 */
static void tile_net_unregister(void *dev_ptr)
{
    struct net_device *dev = (struct net_device *)dev_ptr;
    struct tile_net_priv *priv = netdev_priv(dev);
    int my_cpu = smp_processor_id();
    struct tile_net_cpu *info = priv->cpu[my_cpu];

    int ret;
    int dummy = 0;

    /* Disable the ingress interrupt. */
    disable_percpu_irq(priv->intr_id);

    /* Do nothing else if not registered. */
    if (info == NULL || !info->registered)
        return;

    /* Unregister ourselves with LIPP/LEPP. */
    ret = hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
                sizeof(dummy), NETIO_IPP_INPUT_UNREGISTER_OFF);
    if (ret < 0)
        panic("Failed to unregister with LIPP/LEPP!\n");

    /* Discard all packets still in our NetIO queue. */
    tile_net_discard_packets(dev);

    /* Reset state. */
    info->num_needed_small_buffers = 0;
    info->num_needed_large_buffers = 0;

    /* Cancel egress timer. */
    del_timer(&info->egress_timer);
    info->egress_timer_scheduled = false;
}


/*
 * Helper function for "tile_net_stop()".
 *
 * Also used to handle registration failure in "tile_net_open_inner()",
 * when the various extra steps in "tile_net_stop()" are not necessary.
 */
static void tile_net_stop_aux(struct net_device *dev)
{
    struct tile_net_priv *priv = netdev_priv(dev);
    int i;

    int dummy = 0;

    /*
     * Unregister all tiles, so LIPP will stop delivering packets.
     * Also, delete all the "napi" objects (sequentially, to protect
     * "dev->napi_list").
     */
    on_each_cpu(tile_net_unregister, (void *)dev, 1);
    for_each_online_cpu(i) {
        struct tile_net_cpu *info = priv->cpu[i];
        if (info != NULL && info->registered) {
            netif_napi_del(&info->napi);
            info->registered = false;
        }
    }

    /* Stop LIPP/LEPP. */
    if (hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
              sizeof(dummy), NETIO_IPP_STOP_SHIM_OFF) < 0)
        panic("Failed to stop LIPP/LEPP!\n");

    priv->partly_opened = false;
}


/*
 * Disable NAPI for the given device on the current cpu.
 */
static void tile_net_stop_disable(void *dev_ptr)
{
    struct net_device *dev = (struct net_device *)dev_ptr;
    struct tile_net_priv *priv = netdev_priv(dev);
    int my_cpu = smp_processor_id();
    struct tile_net_cpu *info = priv->cpu[my_cpu];

    /* Disable NAPI if needed. */
    if (info != NULL && info->napi_enabled) {
        napi_disable(&info->napi);
        info->napi_enabled = false;
    }
}


/*
 * Enable NAPI and the ingress interrupt for the given device
 * on the current cpu.
 *
 * ISSUE: Only do this for "network cpus"?
 */
static void tile_net_open_enable(void *dev_ptr)
{
    struct net_device *dev = (struct net_device *)dev_ptr;
    struct tile_net_priv *priv = netdev_priv(dev);
    int my_cpu = smp_processor_id();
    struct tile_net_cpu *info = priv->cpu[my_cpu];

    /* Enable NAPI. */
    napi_enable(&info->napi);
    info->napi_enabled = true;

    /* Enable the ingress interrupt. */
    enable_percpu_irq(priv->intr_id, 0);
}


/*
 * tile_net_open_inner does most of the work of bringing up the interface.
 * It's called from tile_net_open(), and also from tile_net_retry_open().
 * The return value is 0 if the interface was brought up, < 0 if
 * tile_net_open() should return the return value as an error, and > 0 if
 * tile_net_open() should return success and schedule a work item to
 * periodically retry the bringup.
 */
static int tile_net_open_inner(struct net_device *dev)
{
    struct tile_net_priv *priv = netdev_priv(dev);
    int my_cpu = smp_processor_id();
    struct tile_net_cpu *info;
    struct tile_netio_queue *queue;
    int result = 0;
    int i;
    int dummy = 0;

    /*
     * First try to register just on the local CPU, and handle any
     * semi-expected "link down" failure specially.  Note that we
     * do NOT call "tile_net_stop_aux()", unlike below.
     */
    tile_net_register(dev);
    info = priv->cpu[my_cpu];
    if (!info->registered) {
        if (info->link_down)
            return 1;
        return -EAGAIN;
    }

    /*
     * Now register everywhere else.  If any registration fails,
     * even for "link down" (which might not be possible), we
     * clean up using "tile_net_stop_aux()".  Also, add all the
     * "napi" objects (sequentially, to protect "dev->napi_list").
     * ISSUE: Only use "netif_napi_add()" for "network cpus"?
     */
    smp_call_function(tile_net_register, (void *)dev, 1);
    for_each_online_cpu(i) {
        struct tile_net_cpu *info = priv->cpu[i];
        if (info->registered)
            netif_napi_add(dev, &info->napi, tile_net_poll, 64);
        else
            result = -EAGAIN;
    }
    if (result != 0) {
        tile_net_stop_aux(dev);
        return result;
    }

    queue = &info->queue;

    if (priv->intr_id == 0) {
        unsigned int irq;

        /*
         * Acquire the irq allocated by the hypervisor.  Every
         * queue gets the same irq.  The "__intr_id" field is
         * "1 << irq", so we use "__ffs()" to extract "irq".
         */
        priv->intr_id = queue->__system_part->__intr_id;
        BUG_ON(priv->intr_id == 0);
        irq = __ffs(priv->intr_id);

        /*
         * Register the ingress interrupt handler for this
         * device, permanently.
         *
         * We used to call "free_irq()" in "tile_net_stop()",
         * and then re-register the handler here every time,
         * but that caused DNP errors in "handle_IRQ_event()"
         * because "desc->action" was NULL.  See bug 9143.
         */
        tile_irq_activate(irq, TILE_IRQ_PERCPU);
        BUG_ON(request_irq(irq, tile_net_handle_ingress_interrupt,
                   0, dev->name, (void *)dev) != 0);
    }

    {
        /* Allocate initial buffers. */

        int max_buffers =
            priv->network_cpus_count * priv->network_cpus_credits;

        info->num_needed_small_buffers =
            min(LIPP_SMALL_BUFFERS, max_buffers);

        info->num_needed_large_buffers =
            min(LIPP_LARGE_BUFFERS, max_buffers);

        tile_net_provide_needed_buffers(info);

        if (info->num_needed_small_buffers != 0 ||
            info->num_needed_large_buffers != 0)
            panic("Insufficient memory for buffer stack!");
    }

    /* We are about to be active. */
    priv->active = true;

    /* Make sure "active" is visible to all tiles. */
    mb();

    /* On each tile, enable NAPI and the ingress interrupt. */
    on_each_cpu(tile_net_open_enable, (void *)dev, 1);

    /* Start LIPP/LEPP and activate "ingress" at the shim. */
    if (hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
              sizeof(dummy), NETIO_IPP_INPUT_INIT_OFF) < 0)
        panic("Failed to activate the LIPP Shim!\n");

    /* Start our transmit queue. */
    netif_start_queue(dev);

    return 0;
}


/*
 * Called periodically to retry bringing up the NetIO interface,
 * if it doesn't come up cleanly during tile_net_open().
 */
static void tile_net_open_retry(struct work_struct *w)
{
    struct delayed_work *dw =
        container_of(w, struct delayed_work, work);

    struct tile_net_priv *priv =
        container_of(dw, struct tile_net_priv, retry_work);

    /*
     * Try to bring the NetIO interface up.  If it fails, reschedule
     * ourselves to try again later; otherwise, tell Linux we now have
     * a working link.  ISSUE: What if the return value is negative?
     */
    if (tile_net_open_inner(priv->dev) != 0)
        schedule_delayed_work(&priv->retry_work,
                      TILE_NET_RETRY_INTERVAL);
    else
        netif_carrier_on(priv->dev);
}


/*
 * Called when a network interface is made active.
 *
 * Returns 0 on success, negative value on failure.
 *
 * The open entry point is called when a network interface is made
 * active by the system (IFF_UP).  At this point all resources needed
 * for transmit and receive operations are allocated, the interrupt
 * handler is registered with the OS (if needed), the watchdog timer
 * is started, and the stack is notified that the interface is ready.
 *
 * If the actual link is not available yet, then we tell Linux that
 * we have no carrier, and we keep checking until the link comes up.
 */
static int tile_net_open(struct net_device *dev)
{
    int ret = 0;
    struct tile_net_priv *priv = netdev_priv(dev);

    /*
     * We rely on priv->partly_opened to tell us if this is the
     * first time this interface is being brought up. If it is
     * set, the IPP was already initialized and should not be
     * initialized again.
     */
    if (!priv->partly_opened) {

        int count;
        int credits;

        /* Initialize LIPP/LEPP, and start the Shim. */
        ret = tile_net_open_aux(dev);
        if (ret < 0) {
            pr_err("tile_net_open_aux failed: %d\n", ret);
            return ret;
        }

        /* Analyze the network cpus. */

        if (network_cpus_used)
            cpumask_copy(&priv->network_cpus_map,
                     &network_cpus_map);
        else
            cpumask_copy(&priv->network_cpus_map, cpu_online_mask);


        count = cpumask_weight(&priv->network_cpus_map);

        /* Limit credits to available buffers, and apply min. */
        credits = max(16, (LIPP_LARGE_BUFFERS / count) & ~1);

        /* Apply "GBE" max limit. */
        /* ISSUE: Use higher limit for XGBE? */
        credits = min(NETIO_MAX_RECEIVE_PKTS, credits);

        priv->network_cpus_count = count;
        priv->network_cpus_credits = credits;

#ifdef TILE_NET_DEBUG
        pr_info("Using %d network cpus, with %d credits each\n",
               priv->network_cpus_count, priv->network_cpus_credits);
#endif

        priv->partly_opened = true;

    } else {
        /* FIXME: Is this possible? */
        /* printk("Already partly opened.\n"); */
    }

    /*
     * Attempt to bring up the link.
     */
    ret = tile_net_open_inner(dev);
    if (ret <= 0) {
        if (ret == 0)
            netif_carrier_on(dev);
        return ret;
    }

    /*
     * We were unable to bring up the NetIO interface, but we want to
     * try again in a little bit.  Tell Linux that we have no carrier
     * so it doesn't try to use the interface before the link comes up
     * and then remember to try again later.
     */
    netif_carrier_off(dev);
    schedule_delayed_work(&priv->retry_work, TILE_NET_RETRY_INTERVAL);

    return 0;
}


static int tile_net_drain_lipp_buffers(struct tile_net_priv *priv)
{
    int n = 0;

    /* Drain all the LIPP buffers. */
    while (true) {
        unsigned int buffer;

        /* NOTE: This should never fail. */
        if (hv_dev_pread(priv->hv_devhdl, 0, (HV_VirtAddr)&buffer,
                 sizeof(buffer), NETIO_IPP_DRAIN_OFF) < 0)
            break;

        /* Stop when done. */
        if (buffer == 0)
            break;

        {
            /* Convert "linux_buffer_t" to "va". */
            void *va = __va((phys_addr_t)(buffer >> 1) << 7);

            /* Acquire the associated "skb". */
            struct sk_buff **skb_ptr = va - sizeof(*skb_ptr);
            struct sk_buff *skb = *skb_ptr;

            kfree_skb(skb);
        }

        n++;
    }

    return n;
}


/*
 * Disables a network interface.
 *
 * Returns 0, this is not allowed to fail.
 *
 * The close entry point is called when an interface is de-activated
 * by the OS.  The hardware is still under the drivers control, but
 * needs to be disabled.  A global MAC reset is issued to stop the
 * hardware, and all transmit and receive resources are freed.
 *
 * ISSUE: How closely does "netif_running(dev)" mirror "priv->active"?
 *
 * Before we are called by "__dev_close()", "netif_running()" will
 * have been cleared, so no NEW calls to "tile_net_poll()" will be
 * made by "netpoll_poll_dev()".
 *
 * Often, this can cause some tiles to still have packets in their
 * queues, so we must call "tile_net_discard_packets()" later.
 *
 * Note that some other tile may still be INSIDE "tile_net_poll()",
 * and in fact, many will be, if there is heavy network load.
 *
 * Calling "on_each_cpu(tile_net_stop_disable, (void *)dev, 1)" when
 * any tile is still "napi_schedule()"'d will induce a horrible crash
 * when "msleep()" is called.  This includes tiles which are inside
 * "tile_net_poll()" which have not yet called "napi_complete()".
 *
 * So, we must first try to wait long enough for other tiles to finish
 * with any current "tile_net_poll()" call, and, hopefully, to clear
 * the "scheduled" flag.  ISSUE: It is unclear what happens to tiles
 * which have called "napi_schedule()" but which had not yet tried to
 * call "tile_net_poll()", or which exhausted their budget inside
 * "tile_net_poll()" just before this function was called.
 */
static int tile_net_stop(struct net_device *dev)
{
    struct tile_net_priv *priv = netdev_priv(dev);

    PDEBUG("tile_net_stop()\n");

    /* Start discarding packets. */
    priv->active = false;

    /* Make sure "active" is visible to all tiles. */
    mb();

    /*
     * On each tile, make sure no NEW packets get delivered, and
     * disable the ingress interrupt.
     *
     * Note that the ingress interrupt can fire AFTER this,
     * presumably due to packets which were recently delivered,
     * but it will have no effect.
     */
    on_each_cpu(tile_net_deregister, (void *)dev, 1);

    /* Optimistically drain LIPP buffers. */
    (void)tile_net_drain_lipp_buffers(priv);

    /* ISSUE: Only needed if not yet fully open. */
    cancel_delayed_work_sync(&priv->retry_work);

    /* Can't transmit any more. */
    netif_stop_queue(dev);

    /* Disable NAPI on each tile. */
    on_each_cpu(tile_net_stop_disable, (void *)dev, 1);

    /*
     * Drain any remaining LIPP buffers.  NOTE: This "printk()"
     * has never been observed, but in theory it could happen.
     */
    if (tile_net_drain_lipp_buffers(priv) != 0)
        printk("Had to drain some extra LIPP buffers!\n");

    /* Stop LIPP/LEPP. */
    tile_net_stop_aux(dev);

    /*
     * ISSUE: It appears that, in practice anyway, by the time we
     * get here, there are no pending completions, but just in case,
     * we free (all of) them anyway.
     */
    while (tile_net_lepp_free_comps(dev, true))
        /* loop */;

    /* Wipe the EPP queue, and wait till the stores hit the EPP. */
    memset(priv->eq, 0, sizeof(lepp_queue_t));
    mb();

    return 0;
}


/*
 * Prepare the "frags" info for the resulting LEPP command.
 *
 * If needed, flush the memory used by the frags.
 */
static unsigned int tile_net_tx_frags(lepp_frag_t *frags,
                      struct sk_buff *skb,
                      void *b_data, unsigned int b_len)
{
    unsigned int i, n = 0;

    struct skb_shared_info *sh = skb_shinfo(skb);

    phys_addr_t cpa;

    if (b_len != 0) {

        if (!hash_default)
            finv_buffer_remote(b_data, b_len, 0);

        cpa = __pa(b_data);
        frags[n].cpa_lo = cpa;
        frags[n].cpa_hi = cpa >> 32;
        frags[n].length = b_len;
        frags[n].hash_for_home = hash_default;
        n++;
    }

    for (i = 0; i < sh->nr_frags; i++) {

        skb_frag_t *f = &sh->frags[i];
        unsigned long pfn = page_to_pfn(skb_frag_page(f));

        /* FIXME: Compute "hash_for_home" properly. */
        /* ISSUE: The hypervisor checks CHIP_HAS_REV1_DMA_PACKETS(). */
        int hash_for_home = hash_default;

        /* FIXME: Hmmm. */
        if (!hash_default) {
            void *va = pfn_to_kaddr(pfn) + f->page_offset;
            BUG_ON(PageHighMem(skb_frag_page(f)));
            finv_buffer_remote(va, skb_frag_size(f), 0);
        }

        cpa = ((phys_addr_t)pfn << PAGE_SHIFT) + f->page_offset;
        frags[n].cpa_lo = cpa;
        frags[n].cpa_hi = cpa >> 32;
        frags[n].length = skb_frag_size(f);
        frags[n].hash_for_home = hash_for_home;
        n++;
    }

    return n;
}


/*
 * This function takes "skb", consisting of a header template and a
 * payload, and hands it to LEPP, to emit as one or more segments,
 * each consisting of a possibly modified header, plus a piece of the
 * payload, via a process known as "tcp segmentation offload".
 *
 * Usually, "data" will contain the header template, of size "sh_len",
 * and "sh->frags" will contain "skb->data_len" bytes of payload, and
 * there will be "sh->gso_segs" segments.
 *
 * Sometimes, if "sendfile()" requires copying, we will be called with
 * "data" containing the header and payload, with "frags" being empty.
 *
 * Sometimes, for example when using NFS over TCP, a single segment can
 * span 3 fragments, which must be handled carefully in LEPP.
 *
 * See "emulate_large_send_offload()" for some reference code, which
 * does not handle checksumming.
 *
 * ISSUE: How do we make sure that high memory DMA does not migrate?
 */
static int tile_net_tx_tso(struct sk_buff *skb, struct net_device *dev)
{
    struct tile_net_priv *priv = netdev_priv(dev);
    int my_cpu = smp_processor_id();
    struct tile_net_cpu *info = priv->cpu[my_cpu];
    struct tile_net_stats_t *stats = &info->stats;

    struct skb_shared_info *sh = skb_shinfo(skb);

    unsigned char *data = skb->data;

    /* The ip header follows the ethernet header. */
    struct iphdr *ih = ip_hdr(skb);
    unsigned int ih_len = ih->ihl * 4;

    /* Note that "nh == ih", by definition. */
    unsigned char *nh = skb_network_header(skb);
    unsigned int eh_len = nh - data;

    /* The tcp header follows the ip header. */
    struct tcphdr *th = (struct tcphdr *)(nh + ih_len);
    unsigned int th_len = th->doff * 4;

    /* The total number of header bytes. */
    /* NOTE: This may be less than skb_headlen(skb). */
    unsigned int sh_len = eh_len + ih_len + th_len;

    /* The number of payload bytes at "skb->data + sh_len". */
    /* This is non-zero for sendfile() without HIGHDMA. */
    unsigned int b_len = skb_headlen(skb) - sh_len;

    /* The total number of payload bytes. */
    unsigned int d_len = b_len + skb->data_len;

    /* The maximum payload size. */
    unsigned int p_len = sh->gso_size;

    /* The total number of segments. */
    unsigned int num_segs = sh->gso_segs;

    /* The temporary copy of the command. */
    u32 cmd_body[(LEPP_MAX_CMD_SIZE + 3) / 4];
    lepp_tso_cmd_t *cmd = (lepp_tso_cmd_t *)cmd_body;

    /* Analyze the "frags". */
    unsigned int num_frags =
        tile_net_tx_frags(cmd->frags, skb, data + sh_len, b_len);

    /* The size of the command, including frags and header. */
    size_t cmd_size = LEPP_TSO_CMD_SIZE(num_frags, sh_len);

    /* The command header. */
    lepp_tso_cmd_t cmd_init = {
        .tso = true,
        .header_size = sh_len,
        .ip_offset = eh_len,
        .tcp_offset = eh_len + ih_len,
        .payload_size = p_len,
        .num_frags = num_frags,
    };

    unsigned long irqflags;

    lepp_queue_t *eq = priv->eq;

    struct sk_buff *olds[8];
    unsigned int wanted = 8;
    unsigned int i, nolds = 0;

    unsigned int cmd_head, cmd_tail, cmd_next;
    unsigned int comp_tail;


    /* Paranoia. */
    BUG_ON(skb->protocol != htons(ETH_P_IP));
    BUG_ON(ih->protocol != IPPROTO_TCP);
    BUG_ON(skb->ip_summed != CHECKSUM_PARTIAL);
    BUG_ON(num_frags > LEPP_MAX_FRAGS);
    /*--BUG_ON(num_segs != (d_len + (p_len - 1)) / p_len); */
    BUG_ON(num_segs <= 1);


    /* Finish preparing the command. */

    /* Copy the command header. */
    *cmd = cmd_init;

    /* Copy the "header". */
    memcpy(&cmd->frags[num_frags], data, sh_len);


    /* Prefetch and wait, to minimize time spent holding the spinlock. */
    prefetch_L1(&eq->comp_tail);
    prefetch_L1(&eq->cmd_tail);
    mb();


    /* Enqueue the command. */

    spin_lock_irqsave(&priv->eq_lock, irqflags);

    /* Handle completions if needed to make room. */
    /* NOTE: Return NETDEV_TX_BUSY if there is still no room. */
    if (lepp_num_free_comp_slots(eq) == 0) {
        nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 0);
        if (nolds == 0) {
busy:
            spin_unlock_irqrestore(&priv->eq_lock, irqflags);
            return NETDEV_TX_BUSY;
        }
    }

    cmd_head = eq->cmd_head;
    cmd_tail = eq->cmd_tail;

    /* Prepare to advance, detecting full queue. */
    /* NOTE: Return NETDEV_TX_BUSY if the queue is full. */
    cmd_next = cmd_tail + cmd_size;
    if (cmd_tail < cmd_head && cmd_next >= cmd_head)
        goto busy;
    if (cmd_next > LEPP_CMD_LIMIT) {
        cmd_next = 0;
        if (cmd_next == cmd_head)
            goto busy;
    }

    /* Copy the command. */
    memcpy(&eq->cmds[cmd_tail], cmd, cmd_size);

    /* Advance. */
    cmd_tail = cmd_next;

    /* Record "skb" for eventual freeing. */
    comp_tail = eq->comp_tail;
    eq->comps[comp_tail] = skb;
    LEPP_QINC(comp_tail);
    eq->comp_tail = comp_tail;

    /* Flush before allowing LEPP to handle the command. */
    /* ISSUE: Is this the optimal location for the flush? */
    __insn_mf();

    eq->cmd_tail = cmd_tail;

    /* NOTE: Using "4" here is more efficient than "0" or "2", */
    /* and, strangely, more efficient than pre-checking the number */
    /* of available completions, and comparing it to 4. */
    if (nolds == 0)
        nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 4);

    spin_unlock_irqrestore(&priv->eq_lock, irqflags);

    /* Handle completions. */
    for (i = 0; i < nolds; i++)
        kfree_skb(olds[i]);

    /* Update stats. */
    stats->tx_packets += num_segs;
    stats->tx_bytes += (num_segs * sh_len) + d_len;

    /* Make sure the egress timer is scheduled. */
    tile_net_schedule_egress_timer(info);

    return NETDEV_TX_OK;
}


/*
 * Transmit a packet (called by the kernel via "hard_start_xmit" hook).
 */
static int tile_net_tx(struct sk_buff *skb, struct net_device *dev)
{
    struct tile_net_priv *priv = netdev_priv(dev);
    int my_cpu = smp_processor_id();
    struct tile_net_cpu *info = priv->cpu[my_cpu];
    struct tile_net_stats_t *stats = &info->stats;

    unsigned long irqflags;

    struct skb_shared_info *sh = skb_shinfo(skb);

    unsigned int len = skb->len;
    unsigned char *data = skb->data;

    unsigned int csum_start = skb_checksum_start_offset(skb);

    lepp_frag_t frags[LEPP_MAX_FRAGS];

    unsigned int num_frags;

    lepp_queue_t *eq = priv->eq;

    struct sk_buff *olds[8];
    unsigned int wanted = 8;
    unsigned int i, nolds = 0;

    unsigned int cmd_size = sizeof(lepp_cmd_t);

    unsigned int cmd_head, cmd_tail, cmd_next;
    unsigned int comp_tail;

    lepp_cmd_t cmds[LEPP_MAX_FRAGS];


    /*
     * This is paranoia, since we think that if the link doesn't come
     * up, telling Linux we have no carrier will keep it from trying
     * to transmit.  If it does, though, we can't execute this routine,
     * since data structures we depend on aren't set up yet.
     */
    if (!info->registered)
        return NETDEV_TX_BUSY;


    /* Save the timestamp. */
    dev->trans_start = jiffies;


#ifdef TILE_NET_PARANOIA
#if CHIP_HAS_CBOX_HOME_MAP()
    if (hash_default) {
        HV_PTE pte = *virt_to_pte(current->mm, (unsigned long)data);
        if (hv_pte_get_mode(pte) != HV_PTE_MODE_CACHE_HASH_L3)
            panic("Non-HFH egress buffer! VA=%p Mode=%d PTE=%llx",
                  data, hv_pte_get_mode(pte), hv_pte_val(pte));
    }
#endif
#endif


#ifdef TILE_NET_DUMP_PACKETS
    /* ISSUE: Does not dump the "frags". */
    dump_packet(data, skb_headlen(skb), "tx");
#endif /* TILE_NET_DUMP_PACKETS */


    if (sh->gso_size != 0)
        return tile_net_tx_tso(skb, dev);


    /* Prepare the commands. */

    num_frags = tile_net_tx_frags(frags, skb, data, skb_headlen(skb));

    for (i = 0; i < num_frags; i++) {

        bool final = (i == num_frags - 1);

        lepp_cmd_t cmd = {
            .cpa_lo = frags[i].cpa_lo,
            .cpa_hi = frags[i].cpa_hi,
            .length = frags[i].length,
            .hash_for_home = frags[i].hash_for_home,
            .send_completion = final,
            .end_of_packet = final
        };

        if (i == 0 && skb->ip_summed == CHECKSUM_PARTIAL) {
            cmd.compute_checksum = 1;
            cmd.checksum_data.bits.start_byte = csum_start;
            cmd.checksum_data.bits.count = len - csum_start;
            cmd.checksum_data.bits.destination_byte =
                csum_start + skb->csum_offset;
        }

        cmds[i] = cmd;
    }


    /* Prefetch and wait, to minimize time spent holding the spinlock. */
    prefetch_L1(&eq->comp_tail);
    prefetch_L1(&eq->cmd_tail);
    mb();


    /* Enqueue the commands. */

    spin_lock_irqsave(&priv->eq_lock, irqflags);

    /* Handle completions if needed to make room. */
    /* NOTE: Return NETDEV_TX_BUSY if there is still no room. */
    if (lepp_num_free_comp_slots(eq) == 0) {
        nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 0);
        if (nolds == 0) {
busy:
            spin_unlock_irqrestore(&priv->eq_lock, irqflags);
            return NETDEV_TX_BUSY;
        }
    }

    cmd_head = eq->cmd_head;
    cmd_tail = eq->cmd_tail;

    /* Copy the commands, or fail. */
    /* NOTE: Return NETDEV_TX_BUSY if the queue is full. */
    for (i = 0; i < num_frags; i++) {

        /* Prepare to advance, detecting full queue. */
        cmd_next = cmd_tail + cmd_size;
        if (cmd_tail < cmd_head && cmd_next >= cmd_head)
            goto busy;
        if (cmd_next > LEPP_CMD_LIMIT) {
            cmd_next = 0;
            if (cmd_next == cmd_head)
                goto busy;
        }

        /* Copy the command. */
        *(lepp_cmd_t *)&eq->cmds[cmd_tail] = cmds[i];

        /* Advance. */
        cmd_tail = cmd_next;
    }

    /* Record "skb" for eventual freeing. */
    comp_tail = eq->comp_tail;
    eq->comps[comp_tail] = skb;
    LEPP_QINC(comp_tail);
    eq->comp_tail = comp_tail;

    /* Flush before allowing LEPP to handle the command. */
    /* ISSUE: Is this the optimal location for the flush? */
    __insn_mf();

    eq->cmd_tail = cmd_tail;

    /* NOTE: Using "4" here is more efficient than "0" or "2", */
    /* and, strangely, more efficient than pre-checking the number */
    /* of available completions, and comparing it to 4. */
    if (nolds == 0)
        nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 4);

    spin_unlock_irqrestore(&priv->eq_lock, irqflags);

    /* Handle completions. */
    for (i = 0; i < nolds; i++)
        kfree_skb(olds[i]);

    /* HACK: Track "expanded" size for short packets (e.g. 42 < 60). */
    stats->tx_packets++;
    stats->tx_bytes += ((len >= ETH_ZLEN) ? len : ETH_ZLEN);

    /* Make sure the egress timer is scheduled. */
    tile_net_schedule_egress_timer(info);

    return NETDEV_TX_OK;
}


/*
 * Deal with a transmit timeout.
 */
static void tile_net_tx_timeout(struct net_device *dev)
{
    PDEBUG("tile_net_tx_timeout()\n");
    PDEBUG("Transmit timeout at %ld, latency %ld\n", jiffies,
           jiffies - dev->trans_start);

    /* XXX: ISSUE: This doesn't seem useful for us. */
    netif_wake_queue(dev);
}


/*
 * Ioctl commands.
 */
static int tile_net_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
{
    return -EOPNOTSUPP;
}


/*
 * Get System Network Statistics.
 *
 * Returns the address of the device statistics structure.
 */
static struct net_device_stats *tile_net_get_stats(struct net_device *dev)
{
    struct tile_net_priv *priv = netdev_priv(dev);
    u32 rx_packets = 0;
    u32 tx_packets = 0;
    u32 rx_bytes = 0;
    u32 tx_bytes = 0;
    int i;

    for_each_online_cpu(i) {
        if (priv->cpu[i]) {
            rx_packets += priv->cpu[i]->stats.rx_packets;
            rx_bytes += priv->cpu[i]->stats.rx_bytes;
            tx_packets += priv->cpu[i]->stats.tx_packets;
            tx_bytes += priv->cpu[i]->stats.tx_bytes;
        }
    }

    priv->stats.rx_packets = rx_packets;
    priv->stats.rx_bytes = rx_bytes;
    priv->stats.tx_packets = tx_packets;
    priv->stats.tx_bytes = tx_bytes;

    return &priv->stats;
}


/*
 * Change the "mtu".
 *
 * The "change_mtu" method is usually not needed.
 * If you need it, it must be like this.
 */
static int tile_net_change_mtu(struct net_device *dev, int new_mtu)
{
    PDEBUG("tile_net_change_mtu()\n");

    /* Check ranges. */
    if ((new_mtu < 68) || (new_mtu > 1500))
        return -EINVAL;

    /* Accept the value. */
    dev->mtu = new_mtu;

    return 0;
}


/*
 * Change the Ethernet Address of the NIC.
 *
 * The hypervisor driver does not support changing MAC address.  However,
 * the IPP does not do anything with the MAC address, so the address which
 * gets used on outgoing packets, and which is accepted on incoming packets,
 * is completely up to the NetIO program or kernel driver which is actually
 * handling them.
 *
 * Returns 0 on success, negative on failure.
 */
static int tile_net_set_mac_address(struct net_device *dev, void *p)
{
    struct sockaddr *addr = p;

    if (!is_valid_ether_addr(addr->sa_data))
        return -EADDRNOTAVAIL;

    /* ISSUE: Note that "dev_addr" is now a pointer. */
    memcpy(dev->dev_addr, addr->sa_data, dev->addr_len);
    dev->addr_assign_type &= ~NET_ADDR_RANDOM;

    return 0;
}


/*
 * Obtain the MAC address from the hypervisor.
 * This must be done before opening the device.
 */
static int tile_net_get_mac(struct net_device *dev)
{
    struct tile_net_priv *priv = netdev_priv(dev);

    char hv_dev_name[32];
    int len;

    __netio_getset_offset_t offset = { .word = NETIO_IPP_PARAM_OFF };

    int ret;

    /* For example, "xgbe0". */
    strcpy(hv_dev_name, dev->name);
    len = strlen(hv_dev_name);

    /* For example, "xgbe/0". */
    hv_dev_name[len] = hv_dev_name[len - 1];
    hv_dev_name[len - 1] = '/';
    len++;

    /* For example, "xgbe/0/native_hash". */
    strcpy(hv_dev_name + len, hash_default ? "/native_hash" : "/native");

    /* Get the hypervisor handle for this device. */
    priv->hv_devhdl = hv_dev_open((HV_VirtAddr)hv_dev_name, 0);
    PDEBUG("hv_dev_open(%s) returned %d %p\n",
           hv_dev_name, priv->hv_devhdl, &priv->hv_devhdl);
    if (priv->hv_devhdl < 0) {
        if (priv->hv_devhdl == HV_ENODEV)
            printk(KERN_DEBUG "Ignoring unconfigured device %s\n",
                 hv_dev_name);
        else
            printk(KERN_DEBUG "hv_dev_open(%s) returned %d\n",
                 hv_dev_name, priv->hv_devhdl);
        return -1;
    }

    /*
     * Read the hardware address from the hypervisor.
     * ISSUE: Note that "dev_addr" is now a pointer.
     */
    offset.bits.class = NETIO_PARAM;
    offset.bits.addr = NETIO_PARAM_MAC;
    ret = hv_dev_pread(priv->hv_devhdl, 0,
               (HV_VirtAddr)dev->dev_addr, dev->addr_len,
               offset.word);
    PDEBUG("hv_dev_pread(NETIO_PARAM_MAC) returned %d\n", ret);
    if (ret <= 0) {
        printk(KERN_DEBUG "hv_dev_pread(NETIO_PARAM_MAC) %s failed\n",
               dev->name);
        /*
         * Since the device is configured by the hypervisor but we
         * can't get its MAC address, we are most likely running
         * the simulator, so let's generate a random MAC address.
         */
        eth_hw_addr_random(dev);
    }

    return 0;
}


#ifdef CONFIG_NET_POLL_CONTROLLER
/*
 * Polling 'interrupt' - used by things like netconsole to send skbs
 * without having to re-enable interrupts. It's not called while
 * the interrupt routine is executing.
 */
static void tile_net_netpoll(struct net_device *dev)
{
    struct tile_net_priv *priv = netdev_priv(dev);
    disable_percpu_irq(priv->intr_id);
    tile_net_handle_ingress_interrupt(priv->intr_id, dev);
    enable_percpu_irq(priv->intr_id, 0);
}
#endif


static const struct net_device_ops tile_net_ops = {
    .ndo_open = tile_net_open,
    .ndo_stop = tile_net_stop,
    .ndo_start_xmit = tile_net_tx,
    .ndo_do_ioctl = tile_net_ioctl,
    .ndo_get_stats = tile_net_get_stats,
    .ndo_change_mtu = tile_net_change_mtu,
    .ndo_tx_timeout = tile_net_tx_timeout,
    .ndo_set_mac_address = tile_net_set_mac_address,
#ifdef CONFIG_NET_POLL_CONTROLLER
    .ndo_poll_controller = tile_net_netpoll,
#endif
};


/*
 * The setup function.
 *
 * This uses ether_setup() to assign various fields in dev, including
 * setting IFF_BROADCAST and IFF_MULTICAST, then sets some extra fields.
 */
static void tile_net_setup(struct net_device *dev)
{
    PDEBUG("tile_net_setup()\n");

    ether_setup(dev);

    dev->netdev_ops = &tile_net_ops;

    dev->watchdog_timeo = TILE_NET_TIMEOUT;

    /* We want lockless xmit. */
    dev->features |= NETIF_F_LLTX;

    /* We support hardware tx checksums. */
    dev->features |= NETIF_F_HW_CSUM;

    /* We support scatter/gather. */
    dev->features |= NETIF_F_SG;

    /* We support TSO. */
    dev->features |= NETIF_F_TSO;

#ifdef TILE_NET_GSO
    /* We support GSO. */
    dev->features |= NETIF_F_GSO;
#endif

    if (hash_default)
        dev->features |= NETIF_F_HIGHDMA;

    /* ISSUE: We should support NETIF_F_UFO. */

    dev->tx_queue_len = TILE_NET_TX_QUEUE_LEN;

    dev->mtu = TILE_NET_MTU;
}


/*
 * Allocate the device structure, register the device, and obtain the
 * MAC address from the hypervisor.
 */
static struct net_device *tile_net_dev_init(const char *name)
{
    int ret;
    struct net_device *dev;
    struct tile_net_priv *priv;

    /*
     * Allocate the device structure.  This allocates "priv", calls
     * tile_net_setup(), and saves "name".  Normally, "name" is a
     * template, instantiated by register_netdev(), but not for us.
     */
    dev = alloc_netdev(sizeof(*priv), name, tile_net_setup);
    if (!dev) {
        pr_err("alloc_netdev(%s) failed\n", name);
        return NULL;
    }

    priv = netdev_priv(dev);

    /* Initialize "priv". */

    memset(priv, 0, sizeof(*priv));

    /* Save "dev" for "tile_net_open_retry()". */
    priv->dev = dev;

    INIT_DELAYED_WORK(&priv->retry_work, tile_net_open_retry);

    spin_lock_init(&priv->eq_lock);

    /* Allocate "eq". */
    priv->eq_pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, EQ_ORDER);
    if (!priv->eq_pages) {
        free_netdev(dev);
        return NULL;
    }
    priv->eq = page_address(priv->eq_pages);

    /* Register the network device. */
    ret = register_netdev(dev);
    if (ret) {
        pr_err("register_netdev %s failed %d\n", dev->name, ret);
        __free_pages(priv->eq_pages, EQ_ORDER);
        free_netdev(dev);
        return NULL;
    }

    /* Get the MAC address. */
    ret = tile_net_get_mac(dev);
    if (ret < 0) {
        unregister_netdev(dev);
        __free_pages(priv->eq_pages, EQ_ORDER);
        free_netdev(dev);
        return NULL;
    }

    return dev;
}


/*
 * Module cleanup.
 *
 * FIXME: If compiled as a module, this module cannot be "unloaded",
 * because the "ingress interrupt handler" is registered permanently.
 */
static void tile_net_cleanup(void)
{
    int i;

    for (i = 0; i < TILE_NET_DEVS; i++) {
        if (tile_net_devs[i]) {
            struct net_device *dev = tile_net_devs[i];
            struct tile_net_priv *priv = netdev_priv(dev);
            unregister_netdev(dev);
            finv_buffer_remote(priv->eq, EQ_SIZE, 0);
            __free_pages(priv->eq_pages, EQ_ORDER);
            free_netdev(dev);
        }
    }
}


/*
 * Module initialization.
 */
static int tile_net_init_module(void)
{
    pr_info("Tilera Network Driver\n");

    tile_net_devs[0] = tile_net_dev_init("xgbe0");
    tile_net_devs[1] = tile_net_dev_init("xgbe1");
    tile_net_devs[2] = tile_net_dev_init("gbe0");
    tile_net_devs[3] = tile_net_dev_init("gbe1");

    return 0;
}


module_init(tile_net_init_module);
module_exit(tile_net_cleanup);


#ifndef MODULE

/*
 * The "network_cpus" boot argument specifies the cpus that are dedicated
 * to handle ingress packets.
 *
 * The parameter should be in the form "network_cpus=m-n[,x-y]", where
 * m, n, x, y are integer numbers that represent the cpus that can be
 * neither a dedicated cpu nor a dataplane cpu.
 */
static int __init network_cpus_setup(char *str)
{
    int rc = cpulist_parse_crop(str, &network_cpus_map);
    if (rc != 0) {
        pr_warning("network_cpus=%s: malformed cpu list\n",
               str);
    } else {

        /* Remove dedicated cpus. */
        cpumask_and(&network_cpus_map, &network_cpus_map,
                cpu_possible_mask);


        if (cpumask_empty(&network_cpus_map)) {
            pr_warning("Ignoring network_cpus='%s'.\n",
                   str);
        } else {
            char buf[1024];
            cpulist_scnprintf(buf, sizeof(buf), &network_cpus_map);
            pr_info("Linux network CPUs: %s\n", buf);
            network_cpus_used = true;
        }
    }

    return 0;
}
__setup("network_cpus=", network_cpus_setup);

#endif