IB/ipath: Fix RDMA reads

[linux-2.6] / drivers / infiniband / hw / ipath / ipath_rc.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"

/* cut down ridiculously long IB macro names */
#define OP(x) IB_OPCODE_RC_##x

/**
 * ipath_init_restart- initialize the qp->s_sge after a restart
 * @qp: the QP who's SGE we're restarting
 * @wqe: the work queue to initialize the QP's SGE from
 *
 * The QP s_lock should be held and interrupts disabled.
 */
static void ipath_init_restart(struct ipath_qp *qp, struct ipath_swqe *wqe)
{
        struct ipath_ibdev *dev;
        u32 len;

        len = ((qp->s_psn - wqe->psn) & IPATH_PSN_MASK) *
                ib_mtu_enum_to_int(qp->path_mtu);
        qp->s_sge.sge = wqe->sg_list[0];
        qp->s_sge.sg_list = wqe->sg_list + 1;
        qp->s_sge.num_sge = wqe->wr.num_sge;
        ipath_skip_sge(&qp->s_sge, len);
        qp->s_len = wqe->length - len;
        dev = to_idev(qp->ibqp.device);
        spin_lock(&dev->pending_lock);
        if (list_empty(&qp->timerwait))
                list_add_tail(&qp->timerwait,
                              &dev->pending[dev->pending_index]);
        spin_unlock(&dev->pending_lock);
}

/**
 * ipath_make_rc_ack - construct a response packet (ACK, NAK, or RDMA read)
 * @qp: a pointer to the QP
 * @ohdr: a pointer to the IB header being constructed
 * @pmtu: the path MTU
 *
 * Return bth0 if constructed; otherwise, return 0.
 * Note the QP s_lock must be held.
 */
u32 ipath_make_rc_ack(struct ipath_qp *qp,
                      struct ipath_other_headers *ohdr,
                      u32 pmtu)
{
        u32 hwords;
        u32 len;
        u32 bth0;

        /* header size in 32-bit words LRH+BTH = (8+12)/4. */
        hwords = 5;

        /*
         * Send a response.  Note that we are in the responder's
         * side of the QP context.
         */
        switch (qp->s_ack_state) {
        case OP(RDMA_READ_REQUEST):
                qp->s_cur_sge = &qp->s_rdma_sge;
                len = qp->s_rdma_len;
                if (len > pmtu) {
                        len = pmtu;
                        qp->s_ack_state = OP(RDMA_READ_RESPONSE_FIRST);
                } else
                        qp->s_ack_state = OP(RDMA_READ_RESPONSE_ONLY);
                qp->s_rdma_len -= len;
                bth0 = qp->s_ack_state << 24;
                ohdr->u.aeth = ipath_compute_aeth(qp);
                hwords++;
                break;

        case OP(RDMA_READ_RESPONSE_FIRST):
                qp->s_ack_state = OP(RDMA_READ_RESPONSE_MIDDLE);
                /* FALLTHROUGH */
        case OP(RDMA_READ_RESPONSE_MIDDLE):
                qp->s_cur_sge = &qp->s_rdma_sge;
                len = qp->s_rdma_len;
                if (len > pmtu)
                        len = pmtu;
                else {
                        ohdr->u.aeth = ipath_compute_aeth(qp);
                        hwords++;
                        qp->s_ack_state = OP(RDMA_READ_RESPONSE_LAST);
                }
                qp->s_rdma_len -= len;
                bth0 = qp->s_ack_state << 24;
                break;

        case OP(RDMA_READ_RESPONSE_LAST):
        case OP(RDMA_READ_RESPONSE_ONLY):
                /*
                 * We have to prevent new requests from changing
                 * the r_sge state while a ipath_verbs_send()
                 * is in progress.
                 */
                qp->s_ack_state = OP(ACKNOWLEDGE);
                bth0 = 0;
                goto bail;

        case OP(COMPARE_SWAP):
        case OP(FETCH_ADD):
                qp->s_cur_sge = NULL;
                len = 0;
                /*
                 * Set the s_ack_state so the receive interrupt handler
                 * won't try to send an ACK (out of order) until this one
                 * is actually sent.
                 */
                qp->s_ack_state = OP(RDMA_READ_RESPONSE_LAST);
                bth0 = OP(ATOMIC_ACKNOWLEDGE) << 24;
                ohdr->u.at.aeth = ipath_compute_aeth(qp);
                ohdr->u.at.atomic_ack_eth = cpu_to_be64(qp->r_atomic_data);
                hwords += sizeof(ohdr->u.at) / 4;
                break;

        default:
                /* Send a regular ACK. */
                qp->s_cur_sge = NULL;
                len = 0;
                /*
                 * Set the s_ack_state so the receive interrupt handler
                 * won't try to send an ACK (out of order) until this one
                 * is actually sent.
                 */
                qp->s_ack_state = OP(RDMA_READ_RESPONSE_LAST);
                bth0 = OP(ACKNOWLEDGE) << 24;
                if (qp->s_nak_state)
                        ohdr->u.aeth = cpu_to_be32((qp->r_msn & IPATH_MSN_MASK) |
                                                    (qp->s_nak_state <<
                                                     IPATH_AETH_CREDIT_SHIFT));
                else
                        ohdr->u.aeth = ipath_compute_aeth(qp);
                hwords++;
        }
        qp->s_hdrwords = hwords;
        qp->s_cur_size = len;

bail:
        return bth0;
}

/**
 * ipath_make_rc_req - construct a request packet (SEND, RDMA r/w, ATOMIC)
 * @qp: a pointer to the QP
 * @ohdr: a pointer to the IB header being constructed
 * @pmtu: the path MTU
 * @bth0p: pointer to the BTH opcode word
 * @bth2p: pointer to the BTH PSN word
 *
 * Return 1 if constructed; otherwise, return 0.
 * Note the QP s_lock must be held and interrupts disabled.
 */
int ipath_make_rc_req(struct ipath_qp *qp,
                      struct ipath_other_headers *ohdr,
                      u32 pmtu, u32 *bth0p, u32 *bth2p)
{
        struct ipath_ibdev *dev = to_idev(qp->ibqp.device);
        struct ipath_sge_state *ss;
        struct ipath_swqe *wqe;
        u32 hwords;
        u32 len;
        u32 bth0;
        u32 bth2;
        char newreq;

        if (!(ib_ipath_state_ops[qp->state] & IPATH_PROCESS_SEND_OK) ||
            qp->s_rnr_timeout)
                goto done;

        /* Limit the number of packets sent without an ACK. */
        if (ipath_cmp24(qp->s_psn, qp->s_last_psn + IPATH_PSN_CREDIT) > 0) {
                qp->s_wait_credit = 1;
                dev->n_rc_stalls++;
                spin_lock(&dev->pending_lock);
                if (list_empty(&qp->timerwait))
                        list_add_tail(&qp->timerwait,
                                      &dev->pending[dev->pending_index]);
                spin_unlock(&dev->pending_lock);
                goto done;
        }

        /* header size in 32-bit words LRH+BTH = (8+12)/4. */
        hwords = 5;
        bth0 = 0;

        /* Send a request. */
        wqe = get_swqe_ptr(qp, qp->s_cur);
        switch (qp->s_state) {
        default:
                /*
                 * Resend an old request or start a new one.
                 *
                 * We keep track of the current SWQE so that
                 * we don't reset the "furthest progress" state
                 * if we need to back up.
                 */
                newreq = 0;
                if (qp->s_cur == qp->s_tail) {
                        /* Check if send work queue is empty. */
                        if (qp->s_tail == qp->s_head)
                                goto done;
                        wqe->psn = qp->s_next_psn;
                        newreq = 1;
                }
                /*
                 * Note that we have to be careful not to modify the
                 * original work request since we may need to resend
                 * it.
                 */
                len = wqe->length;
                ss = &qp->s_sge;
                bth2 = 0;
                switch (wqe->wr.opcode) {
                case IB_WR_SEND:
                case IB_WR_SEND_WITH_IMM:
                        /* If no credit, return. */
                        if (qp->s_lsn != (u32) -1 &&
                            ipath_cmp24(wqe->ssn, qp->s_lsn + 1) > 0)
                                goto done;
                        wqe->lpsn = wqe->psn;
                        if (len > pmtu) {
                                wqe->lpsn += (len - 1) / pmtu;
                                qp->s_state = OP(SEND_FIRST);
                                len = pmtu;
                                break;
                        }
                        if (wqe->wr.opcode == IB_WR_SEND)
                                qp->s_state = OP(SEND_ONLY);
                        else {
                                qp->s_state = OP(SEND_ONLY_WITH_IMMEDIATE);
                                /* Immediate data comes after the BTH */
                                ohdr->u.imm_data = wqe->wr.imm_data;
                                hwords += 1;
                        }
                        if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                                bth0 |= 1 << 23;
                        bth2 = 1 << 31; /* Request ACK. */
                        if (++qp->s_cur == qp->s_size)
                                qp->s_cur = 0;
                        break;

                case IB_WR_RDMA_WRITE:
                        if (newreq && qp->s_lsn != (u32) -1)
                                qp->s_lsn++;
                        /* FALLTHROUGH */
                case IB_WR_RDMA_WRITE_WITH_IMM:
                        /* If no credit, return. */
                        if (qp->s_lsn != (u32) -1 &&
                            ipath_cmp24(wqe->ssn, qp->s_lsn + 1) > 0)
                                goto done;
                        ohdr->u.rc.reth.vaddr =
                                cpu_to_be64(wqe->wr.wr.rdma.remote_addr);
                        ohdr->u.rc.reth.rkey =
                                cpu_to_be32(wqe->wr.wr.rdma.rkey);
                        ohdr->u.rc.reth.length = cpu_to_be32(len);
                        hwords += sizeof(struct ib_reth) / 4;
                        wqe->lpsn = wqe->psn;
                        if (len > pmtu) {
                                wqe->lpsn += (len - 1) / pmtu;
                                qp->s_state = OP(RDMA_WRITE_FIRST);
                                len = pmtu;
                                break;
                        }
                        if (wqe->wr.opcode == IB_WR_RDMA_WRITE)
                                qp->s_state = OP(RDMA_WRITE_ONLY);
                        else {
                                qp->s_state =
                                        OP(RDMA_WRITE_ONLY_WITH_IMMEDIATE);
                                /* Immediate data comes after RETH */
                                ohdr->u.rc.imm_data = wqe->wr.imm_data;
                                hwords += 1;
                                if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                                        bth0 |= 1 << 23;
                        }
                        bth2 = 1 << 31; /* Request ACK. */
                        if (++qp->s_cur == qp->s_size)
                                qp->s_cur = 0;
                        break;

                case IB_WR_RDMA_READ:
                        ohdr->u.rc.reth.vaddr =
                                cpu_to_be64(wqe->wr.wr.rdma.remote_addr);
                        ohdr->u.rc.reth.rkey =
                                cpu_to_be32(wqe->wr.wr.rdma.rkey);
                        ohdr->u.rc.reth.length = cpu_to_be32(len);
                        qp->s_state = OP(RDMA_READ_REQUEST);
                        hwords += sizeof(ohdr->u.rc.reth) / 4;
                        if (newreq) {
                                if (qp->s_lsn != (u32) -1)
                                        qp->s_lsn++;
                                /*
                                 * Adjust s_next_psn to count the
                                 * expected number of responses.
                                 */
                                if (len > pmtu)
                                        qp->s_next_psn += (len - 1) / pmtu;
                                wqe->lpsn = qp->s_next_psn++;
                        }
                        ss = NULL;
                        len = 0;
                        if (++qp->s_cur == qp->s_size)
                                qp->s_cur = 0;
                        break;

                case IB_WR_ATOMIC_CMP_AND_SWP:
                case IB_WR_ATOMIC_FETCH_AND_ADD:
                        if (wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP)
                                qp->s_state = OP(COMPARE_SWAP);
                        else
                                qp->s_state = OP(FETCH_ADD);
                        ohdr->u.atomic_eth.vaddr = cpu_to_be64(
                                wqe->wr.wr.atomic.remote_addr);
                        ohdr->u.atomic_eth.rkey = cpu_to_be32(
                                wqe->wr.wr.atomic.rkey);
                        ohdr->u.atomic_eth.swap_data = cpu_to_be64(
                                wqe->wr.wr.atomic.swap);
                        ohdr->u.atomic_eth.compare_data = cpu_to_be64(
                                wqe->wr.wr.atomic.compare_add);
                        hwords += sizeof(struct ib_atomic_eth) / 4;
                        if (newreq) {
                                if (qp->s_lsn != (u32) -1)
                                        qp->s_lsn++;
                                wqe->lpsn = wqe->psn;
                        }
                        if (++qp->s_cur == qp->s_size)
                                qp->s_cur = 0;
                        ss = NULL;
                        len = 0;
                        break;

                default:
                        goto done;
                }
                qp->s_sge.sge = wqe->sg_list[0];
                qp->s_sge.sg_list = wqe->sg_list + 1;
                qp->s_sge.num_sge = wqe->wr.num_sge;
                qp->s_len = wqe->length;
                if (newreq) {
                        qp->s_tail++;
                        if (qp->s_tail >= qp->s_size)
                                qp->s_tail = 0;
                }
                bth2 |= qp->s_psn & IPATH_PSN_MASK;
                if (wqe->wr.opcode == IB_WR_RDMA_READ)
                        qp->s_psn = wqe->lpsn + 1;
                else {
                        qp->s_psn++;
                        if ((int)(qp->s_psn - qp->s_next_psn) > 0)
                                qp->s_next_psn = qp->s_psn;
                }
                /*
                 * Put the QP on the pending list so lost ACKs will cause
                 * a retry.  More than one request can be pending so the
                 * QP may already be on the dev->pending list.
                 */
                spin_lock(&dev->pending_lock);
                if (list_empty(&qp->timerwait))
                        list_add_tail(&qp->timerwait,
                                      &dev->pending[dev->pending_index]);
                spin_unlock(&dev->pending_lock);
                break;

        case OP(RDMA_READ_RESPONSE_FIRST):
                /*
                 * This case can only happen if a send is restarted.
                 * See ipath_restart_rc().
                 */
                ipath_init_restart(qp, wqe);
                /* FALLTHROUGH */
        case OP(SEND_FIRST):
                qp->s_state = OP(SEND_MIDDLE);
                /* FALLTHROUGH */
        case OP(SEND_MIDDLE):
                bth2 = qp->s_psn++ & IPATH_PSN_MASK;
                if ((int)(qp->s_psn - qp->s_next_psn) > 0)
                        qp->s_next_psn = qp->s_psn;
                ss = &qp->s_sge;
                len = qp->s_len;
                if (len > pmtu) {
                        len = pmtu;
                        break;
                }
                if (wqe->wr.opcode == IB_WR_SEND)
                        qp->s_state = OP(SEND_LAST);
                else {
                        qp->s_state = OP(SEND_LAST_WITH_IMMEDIATE);
                        /* Immediate data comes after the BTH */
                        ohdr->u.imm_data = wqe->wr.imm_data;
                        hwords += 1;
                }
                if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                        bth0 |= 1 << 23;
                bth2 |= 1 << 31;        /* Request ACK. */
                qp->s_cur++;
                if (qp->s_cur >= qp->s_size)
                        qp->s_cur = 0;
                break;

        case OP(RDMA_READ_RESPONSE_LAST):
                /*
                 * This case can only happen if a RDMA write is restarted.
                 * See ipath_restart_rc().
                 */
                ipath_init_restart(qp, wqe);
                /* FALLTHROUGH */
        case OP(RDMA_WRITE_FIRST):
                qp->s_state = OP(RDMA_WRITE_MIDDLE);
                /* FALLTHROUGH */
        case OP(RDMA_WRITE_MIDDLE):
                bth2 = qp->s_psn++ & IPATH_PSN_MASK;
                if ((int)(qp->s_psn - qp->s_next_psn) > 0)
                        qp->s_next_psn = qp->s_psn;
                ss = &qp->s_sge;
                len = qp->s_len;
                if (len > pmtu) {
                        len = pmtu;
                        break;
                }
                if (wqe->wr.opcode == IB_WR_RDMA_WRITE)
                        qp->s_state = OP(RDMA_WRITE_LAST);
                else {
                        qp->s_state = OP(RDMA_WRITE_LAST_WITH_IMMEDIATE);
                        /* Immediate data comes after the BTH */
                        ohdr->u.imm_data = wqe->wr.imm_data;
                        hwords += 1;
                        if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                                bth0 |= 1 << 23;
                }
                bth2 |= 1 << 31;        /* Request ACK. */
                qp->s_cur++;
                if (qp->s_cur >= qp->s_size)
                        qp->s_cur = 0;
                break;

        case OP(RDMA_READ_RESPONSE_MIDDLE):
                /*
                 * This case can only happen if a RDMA read is restarted.
                 * See ipath_restart_rc().
                 */
                ipath_init_restart(qp, wqe);
                len = ((qp->s_psn - wqe->psn) & IPATH_PSN_MASK) * pmtu;
                ohdr->u.rc.reth.vaddr =
                        cpu_to_be64(wqe->wr.wr.rdma.remote_addr + len);
                ohdr->u.rc.reth.rkey =
                        cpu_to_be32(wqe->wr.wr.rdma.rkey);
                ohdr->u.rc.reth.length = cpu_to_be32(qp->s_len);
                qp->s_state = OP(RDMA_READ_REQUEST);
                hwords += sizeof(ohdr->u.rc.reth) / 4;
                bth2 = qp->s_psn++ & IPATH_PSN_MASK;
                if ((int)(qp->s_psn - qp->s_next_psn) > 0)
                        qp->s_next_psn = qp->s_psn;
                ss = NULL;
                len = 0;
                qp->s_cur++;
                if (qp->s_cur == qp->s_size)
                        qp->s_cur = 0;
                break;

        case OP(RDMA_READ_REQUEST):
        case OP(COMPARE_SWAP):
        case OP(FETCH_ADD):
                /*
                 * We shouldn't start anything new until this request is
                 * finished.  The ACK will handle rescheduling us.  XXX The
                 * number of outstanding ones is negotiated at connection
                 * setup time (see pg. 258,289)?  XXX Also, if we support
                 * multiple outstanding requests, we need to check the WQE
                 * IB_SEND_FENCE flag and not send a new request if a RDMA
                 * read or atomic is pending.
                 */
                goto done;
        }
        if (ipath_cmp24(qp->s_psn, qp->s_last_psn + IPATH_PSN_CREDIT - 1) >= 0)
                bth2 |= 1 << 31;        /* Request ACK. */
        qp->s_len -= len;
        qp->s_hdrwords = hwords;
        qp->s_cur_sge = ss;
        qp->s_cur_size = len;
        *bth0p = bth0 | (qp->s_state << 24);
        *bth2p = bth2;
        return 1;

done:
        return 0;
}

/**
 * send_rc_ack - Construct an ACK packet and send it
 * @qp: a pointer to the QP
 *
 * This is called from ipath_rc_rcv() and only uses the receive
 * side QP state.
 * Note that RDMA reads are handled in the send side QP state and tasklet.
 */
static void send_rc_ack(struct ipath_qp *qp)
{
        struct ipath_ibdev *dev = to_idev(qp->ibqp.device);
        u16 lrh0;
        u32 bth0;
        u32 hwords;
        struct ipath_ib_header hdr;
        struct ipath_other_headers *ohdr;

        /* Construct the header. */
        ohdr = &hdr.u.oth;
        lrh0 = IPATH_LRH_BTH;
        /* header size in 32-bit words LRH+BTH+AETH = (8+12+4)/4. */
        hwords = 6;
        if (unlikely(qp->remote_ah_attr.ah_flags & IB_AH_GRH)) {
                hwords += ipath_make_grh(dev, &hdr.u.l.grh,
                                         &qp->remote_ah_attr.grh,
                                         hwords, 0);
                ohdr = &hdr.u.l.oth;
                lrh0 = IPATH_LRH_GRH;
        }
        /* read pkey_index w/o lock (its atomic) */
        bth0 = ipath_get_pkey(dev->dd, qp->s_pkey_index);
        if (qp->r_nak_state)
                ohdr->u.aeth = cpu_to_be32((qp->r_msn & IPATH_MSN_MASK) |
                                            (qp->r_nak_state <<
                                             IPATH_AETH_CREDIT_SHIFT));
        else
                ohdr->u.aeth = ipath_compute_aeth(qp);
        if (qp->r_ack_state >= OP(COMPARE_SWAP)) {
                bth0 |= OP(ATOMIC_ACKNOWLEDGE) << 24;
                ohdr->u.at.atomic_ack_eth = cpu_to_be64(qp->r_atomic_data);
                hwords += sizeof(ohdr->u.at.atomic_ack_eth) / 4;
        } else
                bth0 |= OP(ACKNOWLEDGE) << 24;
        lrh0 |= qp->remote_ah_attr.sl << 4;
        hdr.lrh[0] = cpu_to_be16(lrh0);
        hdr.lrh[1] = cpu_to_be16(qp->remote_ah_attr.dlid);
        hdr.lrh[2] = cpu_to_be16(hwords + SIZE_OF_CRC);
        hdr.lrh[3] = cpu_to_be16(dev->dd->ipath_lid);
        ohdr->bth[0] = cpu_to_be32(bth0);
        ohdr->bth[1] = cpu_to_be32(qp->remote_qpn);
        ohdr->bth[2] = cpu_to_be32(qp->r_ack_psn & IPATH_PSN_MASK);

        /*
         * If we can send the ACK, clear the ACK state.
         */
        if (ipath_verbs_send(dev->dd, hwords, (u32 *) &hdr, 0, NULL) == 0) {
                qp->r_ack_state = OP(ACKNOWLEDGE);
                dev->n_unicast_xmit++;
        } else {
                /*
                 * We are out of PIO buffers at the moment.
                 * Pass responsibility for sending the ACK to the
                 * send tasklet so that when a PIO buffer becomes
                 * available, the ACK is sent ahead of other outgoing
                 * packets.
                 */
                dev->n_rc_qacks++;
                spin_lock_irq(&qp->s_lock);
                /* Don't coalesce if a RDMA read or atomic is pending. */
                if (qp->s_ack_state == OP(ACKNOWLEDGE) ||
                    qp->s_ack_state < OP(RDMA_READ_REQUEST)) {
                        qp->s_ack_state = qp->r_ack_state;
                        qp->s_nak_state = qp->r_nak_state;
                        qp->s_ack_psn = qp->r_ack_psn;
                        qp->r_ack_state = OP(ACKNOWLEDGE);
                }
                spin_unlock_irq(&qp->s_lock);

                /* Call ipath_do_rc_send() in another thread. */
                tasklet_hi_schedule(&qp->s_task);
        }
}

/**
 * reset_psn - reset the QP state to send starting from PSN
 * @qp: the QP
 * @psn: the packet sequence number to restart at
 *
 * This is called from ipath_rc_rcv() to process an incoming RC ACK
 * for the given QP.
 * Called at interrupt level with the QP s_lock held.
 */
static void reset_psn(struct ipath_qp *qp, u32 psn)
{
        u32 n = qp->s_last;
        struct ipath_swqe *wqe = get_swqe_ptr(qp, n);
        u32 opcode;

        qp->s_cur = n;

        /*
         * If we are starting the request from the beginning,
         * let the normal send code handle initialization.
         */
        if (ipath_cmp24(psn, wqe->psn) <= 0) {
                qp->s_state = OP(SEND_LAST);
                goto done;
        }

        /* Find the work request opcode corresponding to the given PSN. */
        opcode = wqe->wr.opcode;
        for (;;) {
                int diff;

                if (++n == qp->s_size)
                        n = 0;
                if (n == qp->s_tail)
                        break;
                wqe = get_swqe_ptr(qp, n);
                diff = ipath_cmp24(psn, wqe->psn);
                if (diff < 0)
                        break;
                qp->s_cur = n;
                /*
                 * If we are starting the request from the beginning,
                 * let the normal send code handle initialization.
                 */
                if (diff == 0) {
                        qp->s_state = OP(SEND_LAST);
                        goto done;
                }
                opcode = wqe->wr.opcode;
        }

        /*
         * Set the state to restart in the middle of a request.
         * Don't change the s_sge, s_cur_sge, or s_cur_size.
         * See ipath_do_rc_send().
         */
        switch (opcode) {
        case IB_WR_SEND:
        case IB_WR_SEND_WITH_IMM:
                qp->s_state = OP(RDMA_READ_RESPONSE_FIRST);
                break;

        case IB_WR_RDMA_WRITE:
        case IB_WR_RDMA_WRITE_WITH_IMM:
                qp->s_state = OP(RDMA_READ_RESPONSE_LAST);
                break;

        case IB_WR_RDMA_READ:
                qp->s_state = OP(RDMA_READ_RESPONSE_MIDDLE);
                break;

        default:
                /*
                 * This case shouldn't happen since its only
                 * one PSN per req.
                 */
                qp->s_state = OP(SEND_LAST);
        }
done:
        qp->s_psn = psn;
}

/**
 * ipath_restart_rc - back up requester to resend the last un-ACKed request
 * @qp: the QP to restart
 * @psn: packet sequence number for the request
 * @wc: the work completion request
 *
 * The QP s_lock should be held and interrupts disabled.
 */
void ipath_restart_rc(struct ipath_qp *qp, u32 psn, struct ib_wc *wc)
{
        struct ipath_swqe *wqe = get_swqe_ptr(qp, qp->s_last);
        struct ipath_ibdev *dev;

        if (qp->s_retry == 0) {
                wc->wr_id = wqe->wr.wr_id;
                wc->status = IB_WC_RETRY_EXC_ERR;
                wc->opcode = ib_ipath_wc_opcode[wqe->wr.opcode];
                wc->vendor_err = 0;
                wc->byte_len = 0;
                wc->qp_num = qp->ibqp.qp_num;
                wc->src_qp = qp->remote_qpn;
                wc->pkey_index = 0;
                wc->slid = qp->remote_ah_attr.dlid;
                wc->sl = qp->remote_ah_attr.sl;
                wc->dlid_path_bits = 0;
                wc->port_num = 0;
                ipath_sqerror_qp(qp, wc);
                goto bail;
        }
        qp->s_retry--;

        /*
         * Remove the QP from the timeout queue.
         * Note: it may already have been removed by ipath_ib_timer().
         */
        dev = to_idev(qp->ibqp.device);
        spin_lock(&dev->pending_lock);
        if (!list_empty(&qp->timerwait))
                list_del_init(&qp->timerwait);
        spin_unlock(&dev->pending_lock);

        if (wqe->wr.opcode == IB_WR_RDMA_READ)
                dev->n_rc_resends++;
        else
                dev->n_rc_resends += (int)qp->s_psn - (int)psn;

        reset_psn(qp, psn);
        tasklet_hi_schedule(&qp->s_task);

bail:
        return;
}

static inline void update_last_psn(struct ipath_qp *qp, u32 psn)
{
        if (qp->s_wait_credit) {
                qp->s_wait_credit = 0;
                tasklet_hi_schedule(&qp->s_task);
        }
        qp->s_last_psn = psn;
}

/**
 * do_rc_ack - process an incoming RC ACK
 * @qp: the QP the ACK came in on
 * @psn: the packet sequence number of the ACK
 * @opcode: the opcode of the request that resulted in the ACK
 *
 * This is called from ipath_rc_rcv_resp() to process an incoming RC ACK
 * for the given QP.
 * Called at interrupt level with the QP s_lock held and interrupts disabled.
 * Returns 1 if OK, 0 if current operation should be aborted (NAK).
 */
static int do_rc_ack(struct ipath_qp *qp, u32 aeth, u32 psn, int opcode)
{
        struct ipath_ibdev *dev = to_idev(qp->ibqp.device);
        struct ib_wc wc;
        struct ipath_swqe *wqe;
        int ret = 0;
        u32 ack_psn;

        /*
         * Remove the QP from the timeout queue (or RNR timeout queue).
         * If ipath_ib_timer() has already removed it,
         * it's OK since we hold the QP s_lock and ipath_restart_rc()
         * just won't find anything to restart if we ACK everything.
         */
        spin_lock(&dev->pending_lock);
        if (!list_empty(&qp->timerwait))
                list_del_init(&qp->timerwait);
        spin_unlock(&dev->pending_lock);

        /* Nothing is pending to ACK/NAK. */
        if (unlikely(qp->s_last == qp->s_tail))
                goto bail;

        /*
         * Note that NAKs implicitly ACK outstanding SEND and RDMA write
         * requests and implicitly NAK RDMA read and atomic requests issued
         * before the NAK'ed request.  The MSN won't include the NAK'ed
         * request but will include an ACK'ed request(s).
         */
        ack_psn = psn;
        if (aeth >> 29)
                ack_psn--;
        wqe = get_swqe_ptr(qp, qp->s_last);

        /*
         * The MSN might be for a later WQE than the PSN indicates so
         * only complete WQEs that the PSN finishes.
         */
        while (ipath_cmp24(ack_psn, wqe->lpsn) >= 0) {
                /*
                 * If this request is a RDMA read or atomic, and the ACK is
                 * for a later operation, this ACK NAKs the RDMA read or
                 * atomic.  In other words, only a RDMA_READ_LAST or ONLY
                 * can ACK a RDMA read and likewise for atomic ops.  Note
                 * that the NAK case can only happen if relaxed ordering is
                 * used and requests are sent after an RDMA read or atomic
                 * is sent but before the response is received.
                 */
                if ((wqe->wr.opcode == IB_WR_RDMA_READ &&
                     (opcode != OP(RDMA_READ_RESPONSE_LAST) ||
                       ipath_cmp24(ack_psn, wqe->lpsn) != 0)) ||
                    ((wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP ||
                      wqe->wr.opcode == IB_WR_ATOMIC_FETCH_AND_ADD) &&
                     (opcode != OP(ATOMIC_ACKNOWLEDGE) ||
                      ipath_cmp24(wqe->psn, psn) != 0))) {
                        /*
                         * The last valid PSN seen is the previous
                         * request's.
                         */
                        update_last_psn(qp, wqe->psn - 1);
                        /* Retry this request. */
                        ipath_restart_rc(qp, wqe->psn, &wc);
                        /*
                         * No need to process the ACK/NAK since we are
                         * restarting an earlier request.
                         */
                        goto bail;
                }
                if (wqe->wr.opcode == IB_WR_RDMA_READ ||
                    wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP ||
                    wqe->wr.opcode == IB_WR_ATOMIC_FETCH_AND_ADD)
                        tasklet_hi_schedule(&qp->s_task);
                /* Post a send completion queue entry if requested. */
                if (!test_bit(IPATH_S_SIGNAL_REQ_WR, &qp->s_flags) ||
                    (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_num = qp->ibqp.qp_num;
                        wc.src_qp = qp->remote_qpn;
                        wc.pkey_index = 0;
                        wc.slid = qp->remote_ah_attr.dlid;
                        wc.sl = qp->remote_ah_attr.sl;
                        wc.dlid_path_bits = 0;
                        wc.port_num = 0;
                        ipath_cq_enter(to_icq(qp->ibqp.send_cq), &wc, 0);
                }
                qp->s_retry = qp->s_retry_cnt;
                /*
                 * If we are completing a request which is in the process of
                 * being resent, we can stop resending it since we know the
                 * responder has already seen it.
                 */
                if (qp->s_last == qp->s_cur) {
                        if (++qp->s_cur >= qp->s_size)
                                qp->s_cur = 0;
                        wqe = get_swqe_ptr(qp, qp->s_cur);
                        qp->s_state = OP(SEND_LAST);
                        qp->s_psn = wqe->psn;
                }
                if (++qp->s_last >= qp->s_size)
                        qp->s_last = 0;
                wqe = get_swqe_ptr(qp, qp->s_last);
                if (qp->s_last == qp->s_tail)
                        break;
        }

        switch (aeth >> 29) {
        case 0:         /* ACK */
                dev->n_rc_acks++;
                /* If this is a partial ACK, reset the retransmit timer. */
                if (qp->s_last != qp->s_tail) {
                        spin_lock(&dev->pending_lock);
                        list_add_tail(&qp->timerwait,
                                      &dev->pending[dev->pending_index]);
                        spin_unlock(&dev->pending_lock);
                }
                ipath_get_credit(qp, aeth);
                qp->s_rnr_retry = qp->s_rnr_retry_cnt;
                qp->s_retry = qp->s_retry_cnt;
                update_last_psn(qp, psn);
                ret = 1;
                goto bail;

        case 1:         /* RNR NAK */
                dev->n_rnr_naks++;
                if (qp->s_rnr_retry == 0) {
                        if (qp->s_last == qp->s_tail)
                                goto bail;

                        wc.status = IB_WC_RNR_RETRY_EXC_ERR;
                        goto class_b;
                }
                if (qp->s_rnr_retry_cnt < 7)
                        qp->s_rnr_retry--;
                if (qp->s_last == qp->s_tail)
                        goto bail;

                /* The last valid PSN is the previous PSN. */
                update_last_psn(qp, psn - 1);

                dev->n_rc_resends += (int)qp->s_psn - (int)psn;

                reset_psn(qp, psn);

                qp->s_rnr_timeout =
                        ib_ipath_rnr_table[(aeth >> IPATH_AETH_CREDIT_SHIFT) &
                                           IPATH_AETH_CREDIT_MASK];
                ipath_insert_rnr_queue(qp);
                goto bail;

        case 3:         /* NAK */
                /* The last valid PSN seen is the previous request's. */
                if (qp->s_last != qp->s_tail)
                        update_last_psn(qp, wqe->psn - 1);
                switch ((aeth >> IPATH_AETH_CREDIT_SHIFT) &
                        IPATH_AETH_CREDIT_MASK) {
                case 0: /* PSN sequence error */
                        dev->n_seq_naks++;
                        /*
                         * Back up to the responder's expected PSN.  XXX
                         * Note that we might get a NAK in the middle of an
                         * RDMA READ response which terminates the RDMA
                         * READ.
                         */
                        if (qp->s_last == qp->s_tail)
                                break;

                        if (ipath_cmp24(psn, wqe->psn) < 0)
                                break;

                        /* Retry the request. */
                        ipath_restart_rc(qp, psn, &wc);
                        break;

                case 1: /* Invalid Request */
                        wc.status = IB_WC_REM_INV_REQ_ERR;
                        dev->n_other_naks++;
                        goto class_b;

                case 2: /* Remote Access Error */
                        wc.status = IB_WC_REM_ACCESS_ERR;
                        dev->n_other_naks++;
                        goto class_b;

                case 3: /* Remote Operation Error */
                        wc.status = IB_WC_REM_OP_ERR;
                        dev->n_other_naks++;
                class_b:
                        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_num = qp->ibqp.qp_num;
                        wc.src_qp = qp->remote_qpn;
                        wc.pkey_index = 0;
                        wc.slid = qp->remote_ah_attr.dlid;
                        wc.sl = qp->remote_ah_attr.sl;
                        wc.dlid_path_bits = 0;
                        wc.port_num = 0;
                        ipath_sqerror_qp(qp, &wc);
                        break;

                default:
                        /* Ignore other reserved NAK error codes */
                        goto reserved;
                }
                qp->s_rnr_retry = qp->s_rnr_retry_cnt;
                goto bail;

        default:                /* 2: reserved */
        reserved:
                /* Ignore reserved NAK codes. */
                goto bail;
        }

bail:
        return ret;
}

/**
 * ipath_rc_rcv_resp - process an incoming RC response packet
 * @dev: the device this packet came in on
 * @ohdr: the other headers for this packet
 * @data: the packet data
 * @tlen: the packet length
 * @qp: the QP for this packet
 * @opcode: the opcode for this packet
 * @psn: the packet sequence number for this packet
 * @hdrsize: the header length
 * @pmtu: the path MTU
 * @header_in_data: true if part of the header data is in the data buffer
 *
 * This is called from ipath_rc_rcv() to process an incoming RC response
 * packet for the given QP.
 * Called at interrupt level.
 */
static inline void ipath_rc_rcv_resp(struct ipath_ibdev *dev,
                                     struct ipath_other_headers *ohdr,
                                     void *data, u32 tlen,
                                     struct ipath_qp *qp,
                                     u32 opcode,
                                     u32 psn, u32 hdrsize, u32 pmtu,
                                     int header_in_data)
{
        unsigned long flags;
        struct ib_wc wc;
        int diff;
        u32 pad;
        u32 aeth;

        spin_lock_irqsave(&qp->s_lock, flags);

        /* Ignore invalid responses. */
        if (ipath_cmp24(psn, qp->s_next_psn) >= 0)
                goto ack_done;

        /* Ignore duplicate responses. */
        diff = ipath_cmp24(psn, qp->s_last_psn);
        if (unlikely(diff <= 0)) {
                /* Update credits for "ghost" ACKs */
                if (diff == 0 && opcode == OP(ACKNOWLEDGE)) {
                        if (!header_in_data)
                                aeth = be32_to_cpu(ohdr->u.aeth);
                        else {
                                aeth = be32_to_cpu(((__be32 *) data)[0]);
                                data += sizeof(__be32);
                        }
                        if ((aeth >> 29) == 0)
                                ipath_get_credit(qp, aeth);
                }
                goto ack_done;
        }

        switch (opcode) {
        case OP(ACKNOWLEDGE):
        case OP(ATOMIC_ACKNOWLEDGE):
        case OP(RDMA_READ_RESPONSE_FIRST):
                if (!header_in_data)
                        aeth = be32_to_cpu(ohdr->u.aeth);
                else {
                        aeth = be32_to_cpu(((__be32 *) data)[0]);
                        data += sizeof(__be32);
                }
                if (opcode == OP(ATOMIC_ACKNOWLEDGE))
                        *(u64 *) qp->s_sge.sge.vaddr = *(u64 *) data;
                if (!do_rc_ack(qp, aeth, psn, opcode) ||
                    opcode != OP(RDMA_READ_RESPONSE_FIRST))
                        goto ack_done;
                hdrsize += 4;
                /*
                 * do_rc_ack() has already checked the PSN so skip
                 * the sequence check.
                 */
                goto rdma_read;

        case OP(RDMA_READ_RESPONSE_MIDDLE):
                /* no AETH, no ACK */
                if (unlikely(ipath_cmp24(psn, qp->s_last_psn + 1))) {
                        dev->n_rdma_seq++;
                        if (qp->s_last != qp->s_tail)
                                ipath_restart_rc(qp, qp->s_last_psn + 1, &wc);
                        goto ack_done;
                }
        rdma_read:
                if (unlikely(qp->s_state != OP(RDMA_READ_REQUEST)))
                        goto ack_done;
                if (unlikely(tlen != (hdrsize + pmtu + 4)))
                        goto ack_done;
                if (unlikely(pmtu >= qp->s_len))
                        goto ack_done;
                /* We got a response so update the timeout. */
                if (unlikely(qp->s_last == qp->s_tail ||
                             get_swqe_ptr(qp, qp->s_last)->wr.opcode !=
                             IB_WR_RDMA_READ))
                        goto ack_done;
                spin_lock(&dev->pending_lock);
                if (qp->s_rnr_timeout == 0 && !list_empty(&qp->timerwait))
                        list_move_tail(&qp->timerwait,
                                       &dev->pending[dev->pending_index]);
                spin_unlock(&dev->pending_lock);
                /*
                 * Update the RDMA receive state but do the copy w/o
                 * holding the locks and blocking interrupts.
                 * XXX Yet another place that affects relaxed RDMA order
                 * since we don't want s_sge modified.
                 */
                qp->s_len -= pmtu;
                update_last_psn(qp, psn);
                spin_unlock_irqrestore(&qp->s_lock, flags);
                ipath_copy_sge(&qp->s_sge, data, pmtu);
                goto bail;

        case OP(RDMA_READ_RESPONSE_LAST):
                /* ACKs READ req. */
                if (unlikely(ipath_cmp24(psn, qp->s_last_psn + 1))) {
                        dev->n_rdma_seq++;
                        if (qp->s_last != qp->s_tail)
                                ipath_restart_rc(qp, qp->s_last_psn + 1, &wc);
                        goto ack_done;
                }
                /* FALLTHROUGH */
        case OP(RDMA_READ_RESPONSE_ONLY):
                if (unlikely(qp->s_state != OP(RDMA_READ_REQUEST)))
                        goto ack_done;
                /*
                 * Get the number of bytes the message was padded by.
                 */
                pad = (be32_to_cpu(ohdr->bth[0]) >> 20) & 3;
                /*
                 * Check that the data size is >= 1 && <= pmtu.
                 * Remember to account for the AETH header (4) and
                 * ICRC (4).
                 */
                if (unlikely(tlen <= (hdrsize + pad + 8))) {
                        /* XXX Need to generate an error CQ entry. */
                        goto ack_done;
                }
                tlen -= hdrsize + pad + 8;
                if (unlikely(tlen != qp->s_len)) {
                        /* XXX Need to generate an error CQ entry. */
                        goto ack_done;
                }
                if (!header_in_data)
                        aeth = be32_to_cpu(ohdr->u.aeth);
                else {
                        aeth = be32_to_cpu(((__be32 *) data)[0]);
                        data += sizeof(__be32);
                }
                ipath_copy_sge(&qp->s_sge, data, tlen);
                if (do_rc_ack(qp, aeth, psn, OP(RDMA_READ_RESPONSE_LAST))) {
                        /*
                         * Change the state so we contimue
                         * processing new requests and wake up the
                         * tasklet if there are posted sends.
                         */
                        qp->s_state = OP(SEND_LAST);
                        if (qp->s_tail != qp->s_head)
                                tasklet_hi_schedule(&qp->s_task);
                }
                goto ack_done;
        }

ack_done:
        spin_unlock_irqrestore(&qp->s_lock, flags);
bail:
        return;
}

/**
 * ipath_rc_rcv_error - process an incoming duplicate or error RC packet
 * @dev: the device this packet came in on
 * @ohdr: the other headers for this packet
 * @data: the packet data
 * @qp: the QP for this packet
 * @opcode: the opcode for this packet
 * @psn: the packet sequence number for this packet
 * @diff: the difference between the PSN and the expected PSN
 * @header_in_data: true if part of the header data is in the data buffer
 *
 * This is called from ipath_rc_rcv() to process an unexpected
 * incoming RC packet for the given QP.
 * Called at interrupt level.
 * Return 1 if no more processing is needed; otherwise return 0 to
 * schedule a response to be sent and the s_lock unlocked.
 */
static inline int ipath_rc_rcv_error(struct ipath_ibdev *dev,
                                     struct ipath_other_headers *ohdr,
                                     void *data,
                                     struct ipath_qp *qp,
                                     u32 opcode,
                                     u32 psn,
                                     int diff,
                                     int header_in_data)
{
        struct ib_reth *reth;

        if (diff > 0) {
                /*
                 * Packet sequence error.
                 * A NAK will ACK earlier sends and RDMA writes.
                 * Don't queue the NAK if a RDMA read, atomic, or
                 * NAK is pending though.
                 */
                if (qp->s_ack_state != OP(ACKNOWLEDGE) ||
                    qp->r_nak_state != 0)
                        goto done;
                if (qp->r_ack_state < OP(COMPARE_SWAP)) {
                        qp->r_ack_state = OP(SEND_ONLY);
                        qp->r_nak_state = IB_NAK_PSN_ERROR;
                        /* Use the expected PSN. */
                        qp->r_ack_psn = qp->r_psn;
                }
                goto send_ack;
        }

        /*
         * Handle a duplicate request.  Don't re-execute SEND, RDMA
         * write or atomic op.  Don't NAK errors, just silently drop
         * the duplicate request.  Note that r_sge, r_len, and
         * r_rcv_len may be in use so don't modify them.
         *
         * We are supposed to ACK the earliest duplicate PSN but we
         * can coalesce an outstanding duplicate ACK.  We have to
         * send the earliest so that RDMA reads can be restarted at
         * the requester's expected PSN.
         */
        if (opcode == OP(RDMA_READ_REQUEST)) {
                /* RETH comes after BTH */
                if (!header_in_data)
                        reth = &ohdr->u.rc.reth;
                else {
                        reth = (struct ib_reth *)data;
                        data += sizeof(*reth);
                }
                /*
                 * If we receive a duplicate RDMA request, it means the
                 * requester saw a sequence error and needs to restart
                 * from an earlier point.  We can abort the current
                 * RDMA read send in that case.
                 */
                spin_lock_irq(&qp->s_lock);
                if (qp->s_ack_state != OP(ACKNOWLEDGE) &&
                    (qp->s_hdrwords || ipath_cmp24(psn, qp->s_ack_psn) >= 0)) {
                        /*
                         * We are already sending earlier requested data.
                         * Don't abort it to send later out of sequence data.
                         */
                        spin_unlock_irq(&qp->s_lock);
                        goto done;
                }
                qp->s_rdma_len = be32_to_cpu(reth->length);
                if (qp->s_rdma_len != 0) {
                        u32 rkey = be32_to_cpu(reth->rkey);
                        u64 vaddr = be64_to_cpu(reth->vaddr);
                        int ok;

                        /*
                         * Address range must be a subset of the original
                         * request and start on pmtu boundaries.
                         */
                        ok = ipath_rkey_ok(qp, &qp->s_rdma_sge,
                                           qp->s_rdma_len, vaddr, rkey,
                                           IB_ACCESS_REMOTE_READ);
                        if (unlikely(!ok)) {
                                spin_unlock_irq(&qp->s_lock);
                                goto done;
                        }
                } else {
                        qp->s_rdma_sge.sg_list = NULL;
                        qp->s_rdma_sge.num_sge = 0;
                        qp->s_rdma_sge.sge.mr = NULL;
                        qp->s_rdma_sge.sge.vaddr = NULL;
                        qp->s_rdma_sge.sge.length = 0;
                        qp->s_rdma_sge.sge.sge_length = 0;
                }
                qp->s_ack_state = opcode;
                qp->s_ack_psn = psn;
                spin_unlock_irq(&qp->s_lock);
                tasklet_hi_schedule(&qp->s_task);
                goto send_ack;
        }

        /*
         * A pending RDMA read will ACK anything before it so
         * ignore earlier duplicate requests.
         */
        if (qp->s_ack_state != OP(ACKNOWLEDGE))
                goto done;

        /*
         * If an ACK is pending, don't replace the pending ACK
         * with an earlier one since the later one will ACK the earlier.
         * Also, if we already have a pending atomic, send it.
         */
        if (qp->r_ack_state != OP(ACKNOWLEDGE) &&
            (ipath_cmp24(psn, qp->r_ack_psn) <= 0 ||
             qp->r_ack_state >= OP(COMPARE_SWAP)))
                goto send_ack;
        switch (opcode) {
        case OP(COMPARE_SWAP):
        case OP(FETCH_ADD):
                /*
                 * Check for the PSN of the last atomic operation
                 * performed and resend the result if found.
                 */
                if ((psn & IPATH_PSN_MASK) != qp->r_atomic_psn)
                        goto done;
                break;
        }
        qp->r_ack_state = opcode;
        qp->r_nak_state = 0;
        qp->r_ack_psn = psn;
send_ack:
        return 0;

done:
        return 1;
}

static void ipath_rc_error(struct ipath_qp *qp, enum ib_wc_status err)
{
        spin_lock_irq(&qp->s_lock);
        qp->state = IB_QPS_ERR;
        ipath_error_qp(qp, err);
        spin_unlock_irq(&qp->s_lock);
}

/**
 * ipath_rc_rcv - process an incoming RC packet
 * @dev: the device this packet came in on
 * @hdr: the header of this packet
 * @has_grh: true if the header has a GRH
 * @data: the packet data
 * @tlen: the packet length
 * @qp: the QP for this packet
 *
 * This is called from ipath_qp_rcv() to process an incoming RC packet
 * for the given QP.
 * Called at interrupt level.
 */
void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
                  int has_grh, void *data, u32 tlen, struct ipath_qp *qp)
{
        struct ipath_other_headers *ohdr;
        u32 opcode;
        u32 hdrsize;
        u32 psn;
        u32 pad;
        struct ib_wc wc;
        u32 pmtu = ib_mtu_enum_to_int(qp->path_mtu);
        int diff;
        struct ib_reth *reth;
        int header_in_data;

        /* Validate the SLID. See Ch. 9.6.1.5 */
        if (unlikely(be16_to_cpu(hdr->lrh[3]) != qp->remote_ah_attr.dlid))
                goto done;

        /* Check for GRH */
        if (!has_grh) {
                ohdr = &hdr->u.oth;
                hdrsize = 8 + 12;       /* LRH + BTH */
                psn = be32_to_cpu(ohdr->bth[2]);
                header_in_data = 0;
        } else {
                ohdr = &hdr->u.l.oth;
                hdrsize = 8 + 40 + 12;  /* LRH + GRH + BTH */
                /*
                 * The header with GRH is 60 bytes and the core driver sets
                 * the eager header buffer size to 56 bytes so the last 4
                 * bytes of the BTH header (PSN) is in the data buffer.
                 */
                header_in_data = dev->dd->ipath_rcvhdrentsize == 16;
                if (header_in_data) {
                        psn = be32_to_cpu(((__be32 *) data)[0]);
                        data += sizeof(__be32);
                } else
                        psn = be32_to_cpu(ohdr->bth[2]);
        }

        /*
         * Process responses (ACKs) before anything else.  Note that the
         * packet sequence number will be for something in the send work
         * queue rather than the expected receive packet sequence number.
         * In other words, this QP is the requester.
         */
        opcode = be32_to_cpu(ohdr->bth[0]) >> 24;
        if (opcode >= OP(RDMA_READ_RESPONSE_FIRST) &&
            opcode <= OP(ATOMIC_ACKNOWLEDGE)) {
                ipath_rc_rcv_resp(dev, ohdr, data, tlen, qp, opcode, psn,
                                  hdrsize, pmtu, header_in_data);
                goto done;
        }

        /* Compute 24 bits worth of difference. */
        diff = ipath_cmp24(psn, qp->r_psn);
        if (unlikely(diff)) {
                if (ipath_rc_rcv_error(dev, ohdr, data, qp, opcode,
                                       psn, diff, header_in_data))
                        goto done;
                goto send_ack;
        }

        /* Check for opcode sequence errors. */
        switch (qp->r_state) {
        case OP(SEND_FIRST):
        case OP(SEND_MIDDLE):
                if (opcode == OP(SEND_MIDDLE) ||
                    opcode == OP(SEND_LAST) ||
                    opcode == OP(SEND_LAST_WITH_IMMEDIATE))
                        break;
        nack_inv:
                /*
                 * A NAK will ACK earlier sends and RDMA writes.
                 * Don't queue the NAK if a RDMA read, atomic, or NAK
                 * is pending though.
                 */
                if (qp->r_ack_state >= OP(COMPARE_SWAP))
                        goto send_ack;
                ipath_rc_error(qp, IB_WC_REM_INV_REQ_ERR);
                qp->r_ack_state = OP(SEND_ONLY);
                qp->r_nak_state = IB_NAK_INVALID_REQUEST;
                qp->r_ack_psn = qp->r_psn;
                goto send_ack;

        case OP(RDMA_WRITE_FIRST):
        case OP(RDMA_WRITE_MIDDLE):
                if (opcode == OP(RDMA_WRITE_MIDDLE) ||
                    opcode == OP(RDMA_WRITE_LAST) ||
                    opcode == OP(RDMA_WRITE_LAST_WITH_IMMEDIATE))
                        break;
                goto nack_inv;

        default:
                if (opcode == OP(SEND_MIDDLE) ||
                    opcode == OP(SEND_LAST) ||
                    opcode == OP(SEND_LAST_WITH_IMMEDIATE) ||
                    opcode == OP(RDMA_WRITE_MIDDLE) ||
                    opcode == OP(RDMA_WRITE_LAST) ||
                    opcode == OP(RDMA_WRITE_LAST_WITH_IMMEDIATE))
                        goto nack_inv;
                /*
                 * Note that it is up to the requester to not send a new
                 * RDMA read or atomic operation before receiving an ACK
                 * for the previous operation.
                 */
                break;
        }

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

        /* OK, process the packet. */
        switch (opcode) {
        case OP(SEND_FIRST):
                if (!ipath_get_rwqe(qp, 0)) {
                rnr_nak:
                        /*
                         * A RNR NAK will ACK earlier sends and RDMA writes.
                         * Don't queue the NAK if a RDMA read or atomic
                         * is pending though.
                         */
                        if (qp->r_ack_state >= OP(COMPARE_SWAP))
                                goto send_ack;
                        qp->r_ack_state = OP(SEND_ONLY);
                        qp->r_nak_state = IB_RNR_NAK | qp->r_min_rnr_timer;
                        qp->r_ack_psn = qp->r_psn;
                        goto send_ack;
                }
                qp->r_rcv_len = 0;
                /* FALLTHROUGH */
        case OP(SEND_MIDDLE):
        case OP(RDMA_WRITE_MIDDLE):
        send_middle:
                /* Check for invalid length PMTU or posted rwqe len. */
                if (unlikely(tlen != (hdrsize + pmtu + 4)))
                        goto nack_inv;
                qp->r_rcv_len += pmtu;
                if (unlikely(qp->r_rcv_len > qp->r_len))
                        goto nack_inv;
                ipath_copy_sge(&qp->r_sge, data, pmtu);
                break;

        case OP(RDMA_WRITE_LAST_WITH_IMMEDIATE):
                /* consume RWQE */
                if (!ipath_get_rwqe(qp, 1))
                        goto rnr_nak;
                goto send_last_imm;

        case OP(SEND_ONLY):
        case OP(SEND_ONLY_WITH_IMMEDIATE):
                if (!ipath_get_rwqe(qp, 0))
                        goto rnr_nak;
                qp->r_rcv_len = 0;
                if (opcode == OP(SEND_ONLY))
                        goto send_last;
                /* FALLTHROUGH */
        case OP(SEND_LAST_WITH_IMMEDIATE):
        send_last_imm:
                if (header_in_data) {
                        wc.imm_data = *(__be32 *) data;
                        data += sizeof(__be32);
                } else {
                        /* Immediate data comes after BTH */
                        wc.imm_data = ohdr->u.imm_data;
                }
                hdrsize += 4;
                wc.wc_flags = IB_WC_WITH_IMM;
                /* FALLTHROUGH */
        case OP(SEND_LAST):
        case OP(RDMA_WRITE_LAST):
        send_last:
                /* Get the number of bytes the message was padded by. */
                pad = (be32_to_cpu(ohdr->bth[0]) >> 20) & 3;
                /* Check for invalid length. */
                /* XXX LAST len should be >= 1 */
                if (unlikely(tlen < (hdrsize + pad + 4)))
                        goto nack_inv;
                /* Don't count the CRC. */
                tlen -= (hdrsize + pad + 4);
                wc.byte_len = tlen + qp->r_rcv_len;
                if (unlikely(wc.byte_len > qp->r_len))
                        goto nack_inv;
                ipath_copy_sge(&qp->r_sge, data, tlen);
                qp->r_msn++;
                if (!qp->r_wrid_valid)
                        break;
                qp->r_wrid_valid = 0;
                wc.wr_id = qp->r_wr_id;
                wc.status = IB_WC_SUCCESS;
                wc.opcode = IB_WC_RECV;
                wc.vendor_err = 0;
                wc.qp_num = qp->ibqp.qp_num;
                wc.src_qp = qp->remote_qpn;
                wc.pkey_index = 0;
                wc.slid = qp->remote_ah_attr.dlid;
                wc.sl = qp->remote_ah_attr.sl;
                wc.dlid_path_bits = 0;
                wc.port_num = 0;
                /* Signal completion event if the solicited bit is set. */
                ipath_cq_enter(to_icq(qp->ibqp.recv_cq), &wc,
                               (ohdr->bth[0] &
                                __constant_cpu_to_be32(1 << 23)) != 0);
                break;

        case OP(RDMA_WRITE_FIRST):
        case OP(RDMA_WRITE_ONLY):
        case OP(RDMA_WRITE_ONLY_WITH_IMMEDIATE):
                /* consume RWQE */
                /* RETH comes after BTH */
                if (!header_in_data)
                        reth = &ohdr->u.rc.reth;
                else {
                        reth = (struct ib_reth *)data;
                        data += sizeof(*reth);
                }
                hdrsize += sizeof(*reth);
                qp->r_len = be32_to_cpu(reth->length);
                qp->r_rcv_len = 0;
                if (qp->r_len != 0) {
                        u32 rkey = be32_to_cpu(reth->rkey);
                        u64 vaddr = be64_to_cpu(reth->vaddr);
                        int ok;

                        /* Check rkey & NAK */
                        ok = ipath_rkey_ok(qp, &qp->r_sge,
                                           qp->r_len, vaddr, rkey,
                                           IB_ACCESS_REMOTE_WRITE);
                        if (unlikely(!ok))
                                goto nack_acc;
                } else {
                        qp->r_sge.sg_list = NULL;
                        qp->r_sge.sge.mr = NULL;
                        qp->r_sge.sge.vaddr = NULL;
                        qp->r_sge.sge.length = 0;
                        qp->r_sge.sge.sge_length = 0;
                }
                if (unlikely(!(qp->qp_access_flags &
                               IB_ACCESS_REMOTE_WRITE)))
                        goto nack_acc;
                if (opcode == OP(RDMA_WRITE_FIRST))
                        goto send_middle;
                else if (opcode == OP(RDMA_WRITE_ONLY))
                        goto send_last;
                if (!ipath_get_rwqe(qp, 1))
                        goto rnr_nak;
                goto send_last_imm;

        case OP(RDMA_READ_REQUEST):
                /* RETH comes after BTH */
                if (!header_in_data)
                        reth = &ohdr->u.rc.reth;
                else {
                        reth = (struct ib_reth *)data;
                        data += sizeof(*reth);
                }
                if (unlikely(!(qp->qp_access_flags &
                               IB_ACCESS_REMOTE_READ)))
                        goto nack_acc;
                spin_lock_irq(&qp->s_lock);
                qp->s_rdma_len = be32_to_cpu(reth->length);
                if (qp->s_rdma_len != 0) {
                        u32 rkey = be32_to_cpu(reth->rkey);
                        u64 vaddr = be64_to_cpu(reth->vaddr);
                        int ok;

                        /* Check rkey & NAK */
                        ok = ipath_rkey_ok(qp, &qp->s_rdma_sge,
                                           qp->s_rdma_len, vaddr, rkey,
                                           IB_ACCESS_REMOTE_READ);
                        if (unlikely(!ok)) {
                                spin_unlock_irq(&qp->s_lock);
                                goto nack_acc;
                        }
                        /*
                         * Update the next expected PSN.  We add 1 later
                         * below, so only add the remainder here.
                         */
                        if (qp->s_rdma_len > pmtu)
                                qp->r_psn += (qp->s_rdma_len - 1) / pmtu;
                } else {
                        qp->s_rdma_sge.sg_list = NULL;
                        qp->s_rdma_sge.num_sge = 0;
                        qp->s_rdma_sge.sge.mr = NULL;
                        qp->s_rdma_sge.sge.vaddr = NULL;
                        qp->s_rdma_sge.sge.length = 0;
                        qp->s_rdma_sge.sge.sge_length = 0;
                }
                /*
                 * We need to increment the MSN here instead of when we
                 * finish sending the result since a duplicate request would
                 * increment it more than once.
                 */
                qp->r_msn++;

                qp->s_ack_state = opcode;
                qp->s_ack_psn = psn;
                spin_unlock_irq(&qp->s_lock);

                qp->r_psn++;
                qp->r_state = opcode;
                qp->r_nak_state = 0;

                /* Call ipath_do_rc_send() in another thread. */
                tasklet_hi_schedule(&qp->s_task);

                goto done;

        case OP(COMPARE_SWAP):
        case OP(FETCH_ADD): {
                struct ib_atomic_eth *ateth;
                u64 vaddr;
                u64 sdata;
                u32 rkey;

                if (!header_in_data)
                        ateth = &ohdr->u.atomic_eth;
                else {
                        ateth = (struct ib_atomic_eth *)data;
                        data += sizeof(*ateth);
                }
                vaddr = be64_to_cpu(ateth->vaddr);
                if (unlikely(vaddr & (sizeof(u64) - 1)))
                        goto nack_inv;
                rkey = be32_to_cpu(ateth->rkey);
                /* Check rkey & NAK */
                if (unlikely(!ipath_rkey_ok(qp, &qp->r_sge,
                                            sizeof(u64), vaddr, rkey,
                                            IB_ACCESS_REMOTE_ATOMIC)))
                        goto nack_acc;
                if (unlikely(!(qp->qp_access_flags &
                               IB_ACCESS_REMOTE_ATOMIC)))
                        goto nack_acc;
                /* Perform atomic OP and save result. */
                sdata = be64_to_cpu(ateth->swap_data);
                spin_lock_irq(&dev->pending_lock);
                qp->r_atomic_data = *(u64 *) qp->r_sge.sge.vaddr;
                if (opcode == OP(FETCH_ADD))
                        *(u64 *) qp->r_sge.sge.vaddr =
                                qp->r_atomic_data + sdata;
                else if (qp->r_atomic_data ==
                         be64_to_cpu(ateth->compare_data))
                        *(u64 *) qp->r_sge.sge.vaddr = sdata;
                spin_unlock_irq(&dev->pending_lock);
                qp->r_msn++;
                qp->r_atomic_psn = psn & IPATH_PSN_MASK;
                psn |= 1 << 31;
                break;
        }

        default:
                /* Drop packet for unknown opcodes. */
                goto done;
        }
        qp->r_psn++;
        qp->r_state = opcode;
        qp->r_nak_state = 0;
        /* Send an ACK if requested or required. */
        if (psn & (1 << 31)) {
                /*
                 * Coalesce ACKs unless there is a RDMA READ or
                 * ATOMIC pending.
                 */
                if (qp->r_ack_state < OP(COMPARE_SWAP)) {
                        qp->r_ack_state = opcode;
                        qp->r_ack_psn = psn;
                }
                goto send_ack;
        }
        goto done;

nack_acc:
        /*
         * A NAK will ACK earlier sends and RDMA writes.
         * Don't queue the NAK if a RDMA read, atomic, or NAK
         * is pending though.
         */
        if (qp->r_ack_state < OP(COMPARE_SWAP)) {
                ipath_rc_error(qp, IB_WC_REM_ACCESS_ERR);
                qp->r_ack_state = OP(RDMA_WRITE_ONLY);
                qp->r_nak_state = IB_NAK_REMOTE_ACCESS_ERROR;
                qp->r_ack_psn = qp->r_psn;
        }
send_ack:
        /* Send ACK right away unless the send tasklet has a pending ACK. */
        if (qp->s_ack_state == OP(ACKNOWLEDGE))
                send_rc_ack(qp);

done:
        return;
}