drivers/scsi/fnic/cq_desc.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Copyright 2008 Cisco Systems, Inc.  All rights reserved.
   4  * Copyright 2007 Nuova Systems, Inc.  All rights reserved.
   5  */
   6 #ifndef _CQ_DESC_H_
   7 #define _CQ_DESC_H_
   8
   9 /*
  10  * Completion queue descriptor types
  11  */
  12 enum cq_desc_types {
  13         CQ_DESC_TYPE_WQ_ENET = 0,
  14         CQ_DESC_TYPE_DESC_COPY = 1,
  15         CQ_DESC_TYPE_WQ_EXCH = 2,
  16         CQ_DESC_TYPE_RQ_ENET = 3,
  17         CQ_DESC_TYPE_RQ_FCP = 4,
  18 };
  19
  20 /* Completion queue descriptor: 16B
  21  *
  22  * All completion queues have this basic layout.  The
  23  * type_specfic area is unique for each completion
  24  * queue type.
  25  */
  26 struct cq_desc {
  27         __le16 completed_index;
  28         __le16 q_number;
  29         u8 type_specfic[11];
  30         u8 type_color;
  31 };
  32
  33 #define CQ_DESC_TYPE_BITS        4
  34 #define CQ_DESC_TYPE_MASK        ((1 << CQ_DESC_TYPE_BITS) - 1)
  35 #define CQ_DESC_COLOR_MASK       1
  36 #define CQ_DESC_COLOR_SHIFT      7
  37 #define CQ_DESC_Q_NUM_BITS       10
  38 #define CQ_DESC_Q_NUM_MASK       ((1 << CQ_DESC_Q_NUM_BITS) - 1)
  39 #define CQ_DESC_COMP_NDX_BITS    12
  40 #define CQ_DESC_COMP_NDX_MASK    ((1 << CQ_DESC_COMP_NDX_BITS) - 1)
  41
  42 static inline void cq_desc_dec(const struct cq_desc *desc_arg,
  43         u8 *type, u8 *color, u16 *q_number, u16 *completed_index)
  44 {
  45         const struct cq_desc *desc = desc_arg;
  46         const u8 type_color = desc->type_color;
  47
  48         *color = (type_color >> CQ_DESC_COLOR_SHIFT) & CQ_DESC_COLOR_MASK;
  49
  50         /*
  51          * Make sure color bit is read from desc *before* other fields
  52          * are read from desc.  Hardware guarantees color bit is last
  53          * bit (byte) written.  Adding the rmb() prevents the compiler
  54          * and/or CPU from reordering the reads which would potentially
  55          * result in reading stale values.
  56          */
  57
  58         rmb();
  59
  60         *type = type_color & CQ_DESC_TYPE_MASK;
  61         *q_number = le16_to_cpu(desc->q_number) & CQ_DESC_Q_NUM_MASK;
  62         *completed_index = le16_to_cpu(desc->completed_index) &
  63                 CQ_DESC_COMP_NDX_MASK;
  64 }
  65
  66 #endif /* _CQ_DESC_H_ */