LXR linux/drivers/scsi/snic/cq

   1/*
   2 * Copyright 2014 Cisco Systems, Inc.  All rights reserved.
   3 *
   4 * This program is free software; you may redistribute it and/or modify
   5 * it under the terms of the GNU General Public License as published by
   6 * the Free Software Foundation; version 2 of the License.
   7 *
   8 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   9 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  10 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  11 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  12 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  13 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  14 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  15 * SOFTWARE.
  16 */
  17
  18#ifndef _CQ_DESC_H_
  19#define _CQ_DESC_H_
  20
  21/*
  22 * Completion queue descriptor types
  23 */
  24enum cq_desc_types {
  25        CQ_DESC_TYPE_WQ_ENET = 0,
  26        CQ_DESC_TYPE_DESC_COPY = 1,
  27        CQ_DESC_TYPE_WQ_EXCH = 2,
  28        CQ_DESC_TYPE_RQ_ENET = 3,
  29        CQ_DESC_TYPE_RQ_FCP = 4,
  30};
  31
  32/* Completion queue descriptor: 16B
  33 *
  34 * All completion queues have this basic layout.  The
  35 * type_specific area is unique for each completion
  36 * queue type.
  37 */
  38struct cq_desc {
  39        __le16 completed_index;
  40        __le16 q_number;
  41        u8 type_specific[11];
  42        u8 type_color;
  43};
  44
  45#define CQ_DESC_TYPE_BITS        4
  46#define CQ_DESC_TYPE_MASK        ((1 << CQ_DESC_TYPE_BITS) - 1)
  47#define CQ_DESC_COLOR_MASK       1
  48#define CQ_DESC_COLOR_SHIFT      7
  49#define CQ_DESC_Q_NUM_BITS       10
  50#define CQ_DESC_Q_NUM_MASK       ((1 << CQ_DESC_Q_NUM_BITS) - 1)
  51#define CQ_DESC_COMP_NDX_BITS    12
  52#define CQ_DESC_COMP_NDX_MASK    ((1 << CQ_DESC_COMP_NDX_BITS) - 1)
  53
  54static inline void cq_desc_dec(const struct cq_desc *desc_arg,
  55        u8 *type, u8 *color, u16 *q_number, u16 *completed_index)
  56{
  57        const struct cq_desc *desc = desc_arg;
  58        const u8 type_color = desc->type_color;
  59
  60        *color = (type_color >> CQ_DESC_COLOR_SHIFT) & CQ_DESC_COLOR_MASK;
  61
  62        /*
  63         * Make sure color bit is read from desc *before* other fields
  64         * are read from desc.  Hardware guarantees color bit is last
  65         * bit (byte) written.  Adding the rmb() prevents the compiler
  66         * and/or CPU from reordering the reads which would potentially
  67         * result in reading stale values.
  68         */
  69        rmb();
  70
  71        *type = type_color & CQ_DESC_TYPE_MASK;
  72        *q_number = le16_to_cpu(desc->q_number) & CQ_DESC_Q_NUM_MASK;
  73        *completed_index = le16_to_cpu(desc->completed_index) &
  74                CQ_DESC_COMP_NDX_MASK;
  75}
  76
  77#endif /* _CQ_DESC_H_ */
  78