drivers/scsi/snic/cq_desc.h

   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  */
  24 enum 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  */
  38 struct 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
  54 static 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_ */