drivers/infiniband/sw/rdmavt/rc.c

   1 /*
   2  * Copyright(c) 2016 Intel Corporation.
   3  *
   4  * This file is provided under a dual BSD/GPLv2 license.  When using or
   5  * redistributing this file, you may do so under either license.
   6  *
   7  * GPL LICENSE SUMMARY
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of version 2 of the GNU General Public License as
  11  * published by the Free Software Foundation.
  12  *
  13  * This program is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * General Public License for more details.
  17  *
  18  * BSD LICENSE
  19  *
  20  * Redistribution and use in source and binary forms, with or without
  21  * modification, are permitted provided that the following conditions
  22  * are met:
  23  *
  24  *  - Redistributions of source code must retain the above copyright
  25  *    notice, this list of conditions and the following disclaimer.
  26  *  - Redistributions in binary form must reproduce the above copyright
  27  *    notice, this list of conditions and the following disclaimer in
  28  *    the documentation and/or other materials provided with the
  29  *    distribution.
  30  *  - Neither the name of Intel Corporation nor the names of its
  31  *    contributors may be used to endorse or promote products derived
  32  *    from this software without specific prior written permission.
  33  *
  34  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  35  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  36  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  37  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  38  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  39  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  40  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  41  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  42  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  43  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  44  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  45  *
  46  */
  47
  48 #include <rdma/rdma_vt.h>
  49 #include <rdma/ib_hdrs.h>
  50
  51 /*
  52  * Convert the AETH credit code into the number of credits.
  53  */
  54 static const u16 credit_table[31] = {
  55         0,                      /* 0 */
  56         1,                      /* 1 */
  57         2,                      /* 2 */
  58         3,                      /* 3 */
  59         4,                      /* 4 */
  60         6,                      /* 5 */
  61         8,                      /* 6 */
  62         12,                     /* 7 */
  63         16,                     /* 8 */
  64         24,                     /* 9 */
  65         32,                     /* A */
  66         48,                     /* B */
  67         64,                     /* C */
  68         96,                     /* D */
  69         128,                    /* E */
  70         192,                    /* F */
  71         256,                    /* 10 */
  72         384,                    /* 11 */
  73         512,                    /* 12 */
  74         768,                    /* 13 */
  75         1024,                   /* 14 */
  76         1536,                   /* 15 */
  77         2048,                   /* 16 */
  78         3072,                   /* 17 */
  79         4096,                   /* 18 */
  80         6144,                   /* 19 */
  81         8192,                   /* 1A */
  82         12288,                  /* 1B */
  83         16384,                  /* 1C */
  84         24576,                  /* 1D */
  85         32768                   /* 1E */
  86 };
  87
  88 /**
  89  * rvt_compute_aeth - compute the AETH (syndrome + MSN)
  90  * @qp: the queue pair to compute the AETH for
  91  *
  92  * Returns the AETH.
  93  */
  94 __be32 rvt_compute_aeth(struct rvt_qp *qp)
  95 {
  96         u32 aeth = qp->r_msn & IB_MSN_MASK;
  97
  98         if (qp->ibqp.srq) {
  99                 /*
 100                  * Shared receive queues don't generate credits.
 101                  * Set the credit field to the invalid value.
 102                  */
 103                 aeth |= IB_AETH_CREDIT_INVAL << IB_AETH_CREDIT_SHIFT;
 104         } else {
 105                 u32 min, max, x;
 106                 u32 credits;
 107                 struct rvt_rwq *wq = qp->r_rq.wq;
 108                 u32 head;
 109                 u32 tail;
 110
 111                 /* sanity check pointers before trusting them */
 112                 head = wq->head;
 113                 if (head >= qp->r_rq.size)
 114                         head = 0;
 115                 tail = wq->tail;
 116                 if (tail >= qp->r_rq.size)
 117                         tail = 0;
 118                 /*
 119                  * Compute the number of credits available (RWQEs).
 120                  * There is a small chance that the pair of reads are
 121                  * not atomic, which is OK, since the fuzziness is
 122                  * resolved as further ACKs go out.
 123                  */
 124                 credits = head - tail;
 125                 if ((int)credits < 0)
 126                         credits += qp->r_rq.size;
 127                 /*
 128                  * Binary search the credit table to find the code to
 129                  * use.
 130                  */
 131                 min = 0;
 132                 max = 31;
 133                 for (;;) {
 134                         x = (min + max) / 2;
 135                         if (credit_table[x] == credits)
 136                                 break;
 137                         if (credit_table[x] > credits) {
 138                                 max = x;
 139                         } else {
 140                                 if (min == x)
 141                                         break;
 142                                 min = x;
 143                         }
 144                 }
 145                 aeth |= x << IB_AETH_CREDIT_SHIFT;
 146         }
 147         return cpu_to_be32(aeth);
 148 }
 149 EXPORT_SYMBOL(rvt_compute_aeth);
 150
 151 /**
 152  * rvt_get_credit - flush the send work queue of a QP
 153  * @qp: the qp who's send work queue to flush
 154  * @aeth: the Acknowledge Extended Transport Header
 155  *
 156  * The QP s_lock should be held.
 157  */
 158 void rvt_get_credit(struct rvt_qp *qp, u32 aeth)
 159 {
 160         struct rvt_dev_info *rdi = ib_to_rvt(qp->ibqp.device);
 161         u32 credit = (aeth >> IB_AETH_CREDIT_SHIFT) & IB_AETH_CREDIT_MASK;
 162
 163         lockdep_assert_held(&qp->s_lock);
 164         /*
 165          * If the credit is invalid, we can send
 166          * as many packets as we like.  Otherwise, we have to
 167          * honor the credit field.
 168          */
 169         if (credit == IB_AETH_CREDIT_INVAL) {
 170                 if (!(qp->s_flags & RVT_S_UNLIMITED_CREDIT)) {
 171                         qp->s_flags |= RVT_S_UNLIMITED_CREDIT;
 172                         if (qp->s_flags & RVT_S_WAIT_SSN_CREDIT) {
 173                                 qp->s_flags &= ~RVT_S_WAIT_SSN_CREDIT;
 174                                 rdi->driver_f.schedule_send(qp);
 175                         }
 176                 }
 177         } else if (!(qp->s_flags & RVT_S_UNLIMITED_CREDIT)) {
 178                 /* Compute new LSN (i.e., MSN + credit) */
 179                 credit = (aeth + credit_table[credit]) & IB_MSN_MASK;
 180                 if (rvt_cmp_msn(credit, qp->s_lsn) > 0) {
 181                         qp->s_lsn = credit;
 182                         if (qp->s_flags & RVT_S_WAIT_SSN_CREDIT) {
 183                                 qp->s_flags &= ~RVT_S_WAIT_SSN_CREDIT;
 184                                 rdi->driver_f.schedule_send(qp);
 185                         }
 186                 }
 187         }
 188 }
 189 EXPORT_SYMBOL(rvt_get_credit);