[GitHub/mt8127/android_kernel_alcatel_ttab.git] / drivers / infiniband / hw / ipath / ipath_ruc.c

/*
 * Copyright (c) 2006 QLogic, Inc. All rights reserved.
 * Copyright (c) 2005, 2006 PathScale, Inc. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include "ipath_verbs.h"
#include "ipath_kernel.h"

/*
 * Convert the AETH RNR timeout code into the number of milliseconds.
 */
const u32 ib_ipath_rnr_table[32] = {
        656,                    /* 0 */
        1,                      /* 1 */
        1,                      /* 2 */
        1,                      /* 3 */
        1,                      /* 4 */
        1,                      /* 5 */
        1,                      /* 6 */
        1,                      /* 7 */
        1,                      /* 8 */
        1,                      /* 9 */
        1,                      /* A */
        1,                      /* B */
        1,                      /* C */
        1,                      /* D */
        2,                      /* E */
        2,                      /* F */
        3,                      /* 10 */
        4,                      /* 11 */
        6,                      /* 12 */
        8,                      /* 13 */
        11,                     /* 14 */
        16,                     /* 15 */
        21,                     /* 16 */
        31,                     /* 17 */
        41,                     /* 18 */
        62,                     /* 19 */
        82,                     /* 1A */
        123,                    /* 1B */
        164,                    /* 1C */
        246,                    /* 1D */
        328,                    /* 1E */
        492                     /* 1F */
};

/**
 * ipath_insert_rnr_queue - put QP on the RNR timeout list for the device
 * @qp: the QP
 *
 * XXX Use a simple list for now.  We might need a priority
 * queue if we have lots of QPs waiting for RNR timeouts
 * but that should be rare.
 */
void ipath_insert_rnr_queue(struct ipath_qp *qp)
{
        struct ipath_ibdev *dev = to_idev(qp->ibqp.device);
        unsigned long flags;

        spin_lock_irqsave(&dev->pending_lock, flags);
        if (list_empty(&dev->rnrwait))
                list_add(&qp->timerwait, &dev->rnrwait);
        else {
                struct list_head *l = &dev->rnrwait;
                struct ipath_qp *nqp = list_entry(l->next, struct ipath_qp,
                                                  timerwait);

                while (qp->s_rnr_timeout >= nqp->s_rnr_timeout) {
                        qp->s_rnr_timeout -= nqp->s_rnr_timeout;
                        l = l->next;
                        if (l->next == &dev->rnrwait)
                                break;
                        nqp = list_entry(l->next, struct ipath_qp,
                                         timerwait);
                }
                list_add(&qp->timerwait, l);
        }
        spin_unlock_irqrestore(&dev->pending_lock, flags);
}

static int init_sge(struct ipath_qp *qp, struct ipath_rwqe *wqe)
{
        int user = to_ipd(qp->ibqp.pd)->user;
        int i, j, ret;
        struct ib_wc wc;

        qp->r_len = 0;
        for (i = j = 0; i < wqe->num_sge; i++) {
                if (wqe->sg_list[i].length == 0)
                        continue;
                /* Check LKEY */
                if ((user && wqe->sg_list[i].lkey == 0) ||
                    !ipath_lkey_ok(qp, &qp->r_sg_list[j], &wqe->sg_list[i],
                                   IB_ACCESS_LOCAL_WRITE))
                        goto bad_lkey;
                qp->r_len += wqe->sg_list[i].length;
                j++;
        }
        qp->r_sge.sge = qp->r_sg_list[0];
        qp->r_sge.sg_list = qp->r_sg_list + 1;
        qp->r_sge.num_sge = j;
        ret = 1;
        goto bail;

bad_lkey:
        wc.wr_id = wqe->wr_id;
        wc.status = IB_WC_LOC_PROT_ERR;
        wc.opcode = IB_WC_RECV;
        wc.vendor_err = 0;
        wc.byte_len = 0;
        wc.imm_data = 0;
        wc.qp = &qp->ibqp;
        wc.src_qp = 0;
        wc.wc_flags = 0;
        wc.pkey_index = 0;
        wc.slid = 0;
        wc.sl = 0;
        wc.dlid_path_bits = 0;
        wc.port_num = 0;
        /* Signal solicited completion event. */
        ipath_cq_enter(to_icq(qp->ibqp.recv_cq), &wc, 1);
        ret = 0;
bail:
        return ret;
}

/**
 * ipath_get_rwqe - copy the next RWQE into the QP's RWQE
 * @qp: the QP
 * @wr_id_only: update wr_id only, not SGEs
 *
 * Return 0 if no RWQE is available, otherwise return 1.
 *
 * Can be called from interrupt level.
 */
int ipath_get_rwqe(struct ipath_qp *qp, int wr_id_only)
{
        unsigned long flags;
        struct ipath_rq *rq;
        struct ipath_rwq *wq;
        struct ipath_srq *srq;
        struct ipath_rwqe *wqe;
        void (*handler)(struct ib_event *, void *);
        u32 tail;
        int ret;

        if (qp->ibqp.srq) {
                srq = to_isrq(qp->ibqp.srq);
                handler = srq->ibsrq.event_handler;
                rq = &srq->rq;
        } else {
                srq = NULL;
                handler = NULL;
                rq = &qp->r_rq;
        }

        spin_lock_irqsave(&rq->lock, flags);
        wq = rq->wq;
        tail = wq->tail;
        /* Validate tail before using it since it is user writable. */
        if (tail >= rq->size)
                tail = 0;
        do {
                if (unlikely(tail == wq->head)) {
                        spin_unlock_irqrestore(&rq->lock, flags);
                        ret = 0;
                        goto bail;
                }
                wqe = get_rwqe_ptr(rq, tail);
                if (++tail >= rq->size)
                        tail = 0;
        } while (!wr_id_only && !init_sge(qp, wqe));
        qp->r_wr_id = wqe->wr_id;
        wq->tail = tail;

        ret = 1;
        qp->r_wrid_valid = 1;
        if (handler) {
                u32 n;

                /*
                 * validate head pointer value and compute
                 * the number of remaining WQEs.
                 */
                n = wq->head;
                if (n >= rq->size)
                        n = 0;
                if (n < tail)
                        n += rq->size - tail;
                else
                        n -= tail;
                if (n < srq->limit) {
                        struct ib_event ev;

                        srq->limit = 0;
                        spin_unlock_irqrestore(&rq->lock, flags);
                        ev.device = qp->ibqp.device;
                        ev.element.srq = qp->ibqp.srq;
                        ev.event = IB_EVENT_SRQ_LIMIT_REACHED;
                        handler(&ev, srq->ibsrq.srq_context);
                        goto bail;
                }
        }
        spin_unlock_irqrestore(&rq->lock, flags);

bail:
        return ret;
}

/**
 * ipath_ruc_loopback - handle UC and RC lookback requests
 * @sqp: the loopback QP
 *
 * This is called from ipath_do_uc_send() or ipath_do_rc_send() to
 * forward a WQE addressed to the same HCA.
 * Note that although we are single threaded due to the tasklet, we still
 * have to protect against post_send().  We don't have to worry about
 * receive interrupts since this is a connected protocol and all packets
 * will pass through here.
 */
static void ipath_ruc_loopback(struct ipath_qp *sqp)
{
        struct ipath_ibdev *dev = to_idev(sqp->ibqp.device);
        struct ipath_qp *qp;
        struct ipath_swqe *wqe;
        struct ipath_sge *sge;
        unsigned long flags;
        struct ib_wc wc;
        u64 sdata;
        atomic64_t *maddr;

        qp = ipath_lookup_qpn(&dev->qp_table, sqp->remote_qpn);
        if (!qp) {
                dev->n_pkt_drops++;
                return;
        }

again:
        spin_lock_irqsave(&sqp->s_lock, flags);

        if (!(ib_ipath_state_ops[sqp->state] & IPATH_PROCESS_SEND_OK) ||
            qp->s_rnr_timeout) {
                spin_unlock_irqrestore(&sqp->s_lock, flags);
                goto done;
        }

        /* Get the next send request. */
        if (sqp->s_last == sqp->s_head) {
                /* Send work queue is empty. */
                spin_unlock_irqrestore(&sqp->s_lock, flags);
                goto done;
        }

        /*
         * We can rely on the entry not changing without the s_lock
         * being held until we update s_last.
         */
        wqe = get_swqe_ptr(sqp, sqp->s_last);
        spin_unlock_irqrestore(&sqp->s_lock, flags);

        wc.wc_flags = 0;
        wc.imm_data = 0;

        sqp->s_sge.sge = wqe->sg_list[0];
        sqp->s_sge.sg_list = wqe->sg_list + 1;
        sqp->s_sge.num_sge = wqe->wr.num_sge;
        sqp->s_len = wqe->length;
        switch (wqe->wr.opcode) {
        case IB_WR_SEND_WITH_IMM:
                wc.wc_flags = IB_WC_WITH_IMM;
                wc.imm_data = wqe->wr.imm_data;
                /* FALLTHROUGH */
        case IB_WR_SEND:
                if (!ipath_get_rwqe(qp, 0)) {
                rnr_nak:
                        /* Handle RNR NAK */
                        if (qp->ibqp.qp_type == IB_QPT_UC)
                                goto send_comp;
                        if (sqp->s_rnr_retry == 0) {
                                wc.status = IB_WC_RNR_RETRY_EXC_ERR;
                                goto err;
                        }
                        if (sqp->s_rnr_retry_cnt < 7)
                                sqp->s_rnr_retry--;
                        dev->n_rnr_naks++;
                        sqp->s_rnr_timeout =
                                ib_ipath_rnr_table[qp->r_min_rnr_timer];
                        ipath_insert_rnr_queue(sqp);
                        goto done;
                }
                break;

        case IB_WR_RDMA_WRITE_WITH_IMM:
                wc.wc_flags = IB_WC_WITH_IMM;
                wc.imm_data = wqe->wr.imm_data;
                if (!ipath_get_rwqe(qp, 1))
                        goto rnr_nak;
                /* FALLTHROUGH */
        case IB_WR_RDMA_WRITE:
                if (wqe->length == 0)
                        break;
                if (unlikely(!ipath_rkey_ok(qp, &qp->r_sge, wqe->length,
                                            wqe->wr.wr.rdma.remote_addr,
                                            wqe->wr.wr.rdma.rkey,
                                            IB_ACCESS_REMOTE_WRITE))) {
                acc_err:
                        wc.status = IB_WC_REM_ACCESS_ERR;
                err:
                        wc.wr_id = wqe->wr.wr_id;
                        wc.opcode = ib_ipath_wc_opcode[wqe->wr.opcode];
                        wc.vendor_err = 0;
                        wc.byte_len = 0;
                        wc.qp = &sqp->ibqp;
                        wc.src_qp = sqp->remote_qpn;
                        wc.pkey_index = 0;
                        wc.slid = sqp->remote_ah_attr.dlid;
                        wc.sl = sqp->remote_ah_attr.sl;
                        wc.dlid_path_bits = 0;
                        wc.port_num = 0;
                        spin_lock_irqsave(&sqp->s_lock, flags);
                        ipath_sqerror_qp(sqp, &wc);
                        spin_unlock_irqrestore(&sqp->s_lock, flags);
                        goto done;
                }
                break;

        case IB_WR_RDMA_READ:
                if (unlikely(!(qp->qp_access_flags &
                               IB_ACCESS_REMOTE_READ)))
                        goto acc_err;
                if (unlikely(!ipath_rkey_ok(qp, &sqp->s_sge, wqe->length,
                                            wqe->wr.wr.rdma.remote_addr,
                                            wqe->wr.wr.rdma.rkey,
                                            IB_ACCESS_REMOTE_READ)))
                        goto acc_err;
                qp->r_sge.sge = wqe->sg_list[0];
                qp->r_sge.sg_list = wqe->sg_list + 1;
                qp->r_sge.num_sge = wqe->wr.num_sge;
                break;

        case IB_WR_ATOMIC_CMP_AND_SWP:
        case IB_WR_ATOMIC_FETCH_AND_ADD:
                if (unlikely(!(qp->qp_access_flags &
                               IB_ACCESS_REMOTE_ATOMIC)))
                        goto acc_err;
                if (unlikely(!ipath_rkey_ok(qp, &qp->r_sge, sizeof(u64),
                                            wqe->wr.wr.atomic.remote_addr,
                                            wqe->wr.wr.atomic.rkey,
                                            IB_ACCESS_REMOTE_ATOMIC)))
                        goto acc_err;
                /* Perform atomic OP and save result. */
                maddr = (atomic64_t *) qp->r_sge.sge.vaddr;
                sdata = wqe->wr.wr.atomic.compare_add;
                *(u64 *) sqp->s_sge.sge.vaddr =
                        (wqe->wr.opcode == IB_WR_ATOMIC_FETCH_AND_ADD) ?
                        (u64) atomic64_add_return(sdata, maddr) - sdata :
                        (u64) cmpxchg((u64 *) qp->r_sge.sge.vaddr,
                                      sdata, wqe->wr.wr.atomic.swap);
                goto send_comp;

        default:
                goto done;
        }

        sge = &sqp->s_sge.sge;
        while (sqp->s_len) {
                u32 len = sqp->s_len;

                if (len > sge->length)
                        len = sge->length;
                BUG_ON(len == 0);
                ipath_copy_sge(&qp->r_sge, sge->vaddr, len);
                sge->vaddr += len;
                sge->length -= len;
                sge->sge_length -= len;
                if (sge->sge_length == 0) {
                        if (--sqp->s_sge.num_sge)
                                *sge = *sqp->s_sge.sg_list++;
                } else if (sge->length == 0 && sge->mr != NULL) {
                        if (++sge->n >= IPATH_SEGSZ) {
                                if (++sge->m >= sge->mr->mapsz)
                                        break;
                                sge->n = 0;
                        }
                        sge->vaddr =
                                sge->mr->map[sge->m]->segs[sge->n].vaddr;
                        sge->length =
                                sge->mr->map[sge->m]->segs[sge->n].length;
                }
                sqp->s_len -= len;
        }

        if (wqe->wr.opcode == IB_WR_RDMA_WRITE ||
            wqe->wr.opcode == IB_WR_RDMA_READ)
                goto send_comp;

        if (wqe->wr.opcode == IB_WR_RDMA_WRITE_WITH_IMM)
                wc.opcode = IB_WC_RECV_RDMA_WITH_IMM;
        else
                wc.opcode = IB_WC_RECV;
        wc.wr_id = qp->r_wr_id;
        wc.status = IB_WC_SUCCESS;
        wc.vendor_err = 0;
        wc.byte_len = wqe->length;
        wc.qp = &qp->ibqp;
        wc.src_qp = qp->remote_qpn;
        /* XXX do we know which pkey matched? Only needed for GSI. */
        wc.pkey_index = 0;
        wc.slid = qp->remote_ah_attr.dlid;
        wc.sl = qp->remote_ah_attr.sl;
        wc.dlid_path_bits = 0;
        /* Signal completion event if the solicited bit is set. */
        ipath_cq_enter(to_icq(qp->ibqp.recv_cq), &wc,
                       wqe->wr.send_flags & IB_SEND_SOLICITED);

send_comp:
        sqp->s_rnr_retry = sqp->s_rnr_retry_cnt;

        if (!(sqp->s_flags & IPATH_S_SIGNAL_REQ_WR) ||
            (wqe->wr.send_flags & IB_SEND_SIGNALED)) {
                wc.wr_id = wqe->wr.wr_id;
                wc.status = IB_WC_SUCCESS;
                wc.opcode = ib_ipath_wc_opcode[wqe->wr.opcode];
                wc.vendor_err = 0;
                wc.byte_len = wqe->length;
                wc.qp = &sqp->ibqp;
                wc.src_qp = 0;
                wc.pkey_index = 0;
                wc.slid = 0;
                wc.sl = 0;
                wc.dlid_path_bits = 0;
                wc.port_num = 0;
                ipath_cq_enter(to_icq(sqp->ibqp.send_cq), &wc, 0);
        }

        /* Update s_last now that we are finished with the SWQE */
        spin_lock_irqsave(&sqp->s_lock, flags);
        if (++sqp->s_last >= sqp->s_size)
                sqp->s_last = 0;
        spin_unlock_irqrestore(&sqp->s_lock, flags);
        goto again;

done:
        if (atomic_dec_and_test(&qp->refcount))
                wake_up(&qp->wait);
}

static int want_buffer(struct ipath_devdata *dd)
{
        set_bit(IPATH_S_PIOINTBUFAVAIL, &dd->ipath_sendctrl);
        ipath_write_kreg(dd, dd->ipath_kregs->kr_sendctrl,
                         dd->ipath_sendctrl);

        return 0;
}

/**
 * ipath_no_bufs_available - tell the layer driver we need buffers
 * @qp: the QP that caused the problem
 * @dev: the device we ran out of buffers on
 *
 * Called when we run out of PIO buffers.
 */
void ipath_no_bufs_available(struct ipath_qp *qp, struct ipath_ibdev *dev)
{
        unsigned long flags;

        spin_lock_irqsave(&dev->pending_lock, flags);
        if (list_empty(&qp->piowait))
                list_add_tail(&qp->piowait, &dev->piowait);
        spin_unlock_irqrestore(&dev->pending_lock, flags);
        /*
         * Note that as soon as want_buffer() is called and
         * possibly before it returns, ipath_ib_piobufavail()
         * could be called.  If we are still in the tasklet function,
         * tasklet_hi_schedule() will not call us until the next time
         * tasklet_hi_schedule() is called.
         * We clear the tasklet flag now since we are committing to return
         * from the tasklet function.
         */
        clear_bit(IPATH_S_BUSY, &qp->s_busy);
        tasklet_unlock(&qp->s_task);
        want_buffer(dev->dd);
        dev->n_piowait++;
}

/**
 * ipath_post_ruc_send - post RC and UC sends
 * @qp: the QP to post on
 * @wr: the work request to send
 */
int ipath_post_ruc_send(struct ipath_qp *qp, struct ib_send_wr *wr)
{
        struct ipath_swqe *wqe;
        unsigned long flags;
        u32 next;
        int i, j;
        int acc;
        int ret;

        /*
         * Don't allow RDMA reads or atomic operations on UC or
         * undefined operations.
         * Make sure buffer is large enough to hold the result for atomics.
         */
        if (qp->ibqp.qp_type == IB_QPT_UC) {
                if ((unsigned) wr->opcode >= IB_WR_RDMA_READ) {
                        ret = -EINVAL;
                        goto bail;
                }
        } else if ((unsigned) wr->opcode > IB_WR_ATOMIC_FETCH_AND_ADD) {
                ret = -EINVAL;
                goto bail;
        } else if (wr->opcode >= IB_WR_ATOMIC_CMP_AND_SWP &&
                   (wr->num_sge == 0 ||
                    wr->sg_list[0].length < sizeof(u64) ||
                    wr->sg_list[0].addr & (sizeof(u64) - 1))) {
                ret = -EINVAL;
                goto bail;
        } else if (wr->opcode >= IB_WR_RDMA_READ && !qp->s_max_rd_atomic) {
                ret = -EINVAL;
                goto bail;
        }
        /* IB spec says that num_sge == 0 is OK. */
        if (wr->num_sge > qp->s_max_sge) {
                ret = -ENOMEM;
                goto bail;
        }
        spin_lock_irqsave(&qp->s_lock, flags);
        next = qp->s_head + 1;
        if (next >= qp->s_size)
                next = 0;
        if (next == qp->s_last) {
                spin_unlock_irqrestore(&qp->s_lock, flags);
                ret = -EINVAL;
                goto bail;
        }

        wqe = get_swqe_ptr(qp, qp->s_head);
        wqe->wr = *wr;
        wqe->ssn = qp->s_ssn++;
        wqe->sg_list[0].mr = NULL;
        wqe->sg_list[0].vaddr = NULL;
        wqe->sg_list[0].length = 0;
        wqe->sg_list[0].sge_length = 0;
        wqe->length = 0;
        acc = wr->opcode >= IB_WR_RDMA_READ ? IB_ACCESS_LOCAL_WRITE : 0;
        for (i = 0, j = 0; i < wr->num_sge; i++) {
                if (to_ipd(qp->ibqp.pd)->user && wr->sg_list[i].lkey == 0) {
                        spin_unlock_irqrestore(&qp->s_lock, flags);
                        ret = -EINVAL;
                        goto bail;
                }
                if (wr->sg_list[i].length == 0)
                        continue;
                if (!ipath_lkey_ok(qp, &wqe->sg_list[j], &wr->sg_list[i],
                                   acc)) {
                        spin_unlock_irqrestore(&qp->s_lock, flags);
                        ret = -EINVAL;
                        goto bail;
                }
                wqe->length += wr->sg_list[i].length;
                j++;
        }
        wqe->wr.num_sge = j;
        qp->s_head = next;
        spin_unlock_irqrestore(&qp->s_lock, flags);

        ipath_do_ruc_send((unsigned long) qp);

        ret = 0;

bail:
        return ret;
}

/**
 * ipath_make_grh - construct a GRH header
 * @dev: a pointer to the ipath device
 * @hdr: a pointer to the GRH header being constructed
 * @grh: the global route address to send to
 * @hwords: the number of 32 bit words of header being sent
 * @nwords: the number of 32 bit words of data being sent
 *
 * Return the size of the header in 32 bit words.
 */
u32 ipath_make_grh(struct ipath_ibdev *dev, struct ib_grh *hdr,
                   struct ib_global_route *grh, u32 hwords, u32 nwords)
{
        hdr->version_tclass_flow =
                cpu_to_be32((6 << 28) |
                            (grh->traffic_class << 20) |
                            grh->flow_label);
        hdr->paylen = cpu_to_be16((hwords - 2 + nwords + SIZE_OF_CRC) << 2);
        /* next_hdr is defined by C8-7 in ch. 8.4.1 */
        hdr->next_hdr = 0x1B;
        hdr->hop_limit = grh->hop_limit;
        /* The SGID is 32-bit aligned. */
        hdr->sgid.global.subnet_prefix = dev->gid_prefix;
        hdr->sgid.global.interface_id = dev->dd->ipath_guid;
        hdr->dgid = grh->dgid;

        /* GRH header size in 32-bit words. */
        return sizeof(struct ib_grh) / sizeof(u32);
}

/**
 * ipath_do_ruc_send - perform a send on an RC or UC QP
 * @data: contains a pointer to the QP
 *
 * Process entries in the send work queue until credit or queue is
 * exhausted.  Only allow one CPU to send a packet per QP (tasklet).
 * Otherwise, after we drop the QP s_lock, two threads could send
 * packets out of order.
 */
void ipath_do_ruc_send(unsigned long data)
{
        struct ipath_qp *qp = (struct ipath_qp *)data;
        struct ipath_ibdev *dev = to_idev(qp->ibqp.device);
        unsigned long flags;
        u16 lrh0;
        u32 nwords;
        u32 extra_bytes;
        u32 bth0;
        u32 bth2;
        u32 pmtu = ib_mtu_enum_to_int(qp->path_mtu);
        struct ipath_other_headers *ohdr;

        if (test_and_set_bit(IPATH_S_BUSY, &qp->s_busy))
                goto bail;

        if (unlikely(qp->remote_ah_attr.dlid == dev->dd->ipath_lid)) {
                ipath_ruc_loopback(qp);
                goto clear;
        }

        ohdr = &qp->s_hdr.u.oth;
        if (qp->remote_ah_attr.ah_flags & IB_AH_GRH)
                ohdr = &qp->s_hdr.u.l.oth;

again:
        /* Check for a constructed packet to be sent. */
        if (qp->s_hdrwords != 0) {
                /*
                 * If no PIO bufs are available, return.  An interrupt will
                 * call ipath_ib_piobufavail() when one is available.
                 */
                if (ipath_verbs_send(dev->dd, qp->s_hdrwords,
                                     (u32 *) &qp->s_hdr, qp->s_cur_size,
                                     qp->s_cur_sge)) {
                        ipath_no_bufs_available(qp, dev);
                        goto bail;
                }
                dev->n_unicast_xmit++;
                /* Record that we sent the packet and s_hdr is empty. */
                qp->s_hdrwords = 0;
        }

        /*
         * The lock is needed to synchronize between setting
         * qp->s_ack_state, resend timer, and post_send().
         */
        spin_lock_irqsave(&qp->s_lock, flags);

        if (!((qp->ibqp.qp_type == IB_QPT_RC) ?
               ipath_make_rc_req(qp, ohdr, pmtu, &bth0, &bth2) :
               ipath_make_uc_req(qp, ohdr, pmtu, &bth0, &bth2))) {
                /*
                 * Clear the busy bit before unlocking to avoid races with
                 * adding new work queue items and then failing to process
                 * them.
                 */
                clear_bit(IPATH_S_BUSY, &qp->s_busy);
                spin_unlock_irqrestore(&qp->s_lock, flags);
                goto bail;
        }

        spin_unlock_irqrestore(&qp->s_lock, flags);

        /* Construct the header. */
        extra_bytes = (4 - qp->s_cur_size) & 3;
        nwords = (qp->s_cur_size + extra_bytes) >> 2;
        lrh0 = IPATH_LRH_BTH;
        if (unlikely(qp->remote_ah_attr.ah_flags & IB_AH_GRH)) {
                qp->s_hdrwords += ipath_make_grh(dev, &qp->s_hdr.u.l.grh,
                                                 &qp->remote_ah_attr.grh,
                                                 qp->s_hdrwords, nwords);
                lrh0 = IPATH_LRH_GRH;
        }
        lrh0 |= qp->remote_ah_attr.sl << 4;
        qp->s_hdr.lrh[0] = cpu_to_be16(lrh0);
        qp->s_hdr.lrh[1] = cpu_to_be16(qp->remote_ah_attr.dlid);
        qp->s_hdr.lrh[2] = cpu_to_be16(qp->s_hdrwords + nwords +
                                       SIZE_OF_CRC);
        qp->s_hdr.lrh[3] = cpu_to_be16(dev->dd->ipath_lid);
        bth0 |= ipath_get_pkey(dev->dd, qp->s_pkey_index);
        bth0 |= extra_bytes << 20;
        ohdr->bth[0] = cpu_to_be32(bth0);
        ohdr->bth[1] = cpu_to_be32(qp->remote_qpn);
        ohdr->bth[2] = cpu_to_be32(bth2);

        /* Check for more work to do. */
        goto again;

clear:
        clear_bit(IPATH_S_BUSY, &qp->s_busy);
bail:
        return;
}