drivers/net/ethernet/cisco/enic/cq_desc.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Copyright 2008-2010 Cisco Systems, Inc.  All rights reserved.
   4  * Copyright 2007 Nuova Systems, Inc.  All rights reserved.
   5  */
   6
   7 #ifndef _CQ_DESC_H_
   8 #define _CQ_DESC_H_
   9
  10 /*
  11  * Completion queue descriptor types
  12  */
  13 enum cq_desc_types {
  14         CQ_DESC_TYPE_WQ_ENET = 0,
  15         CQ_DESC_TYPE_DESC_COPY = 1,
  16         CQ_DESC_TYPE_WQ_EXCH = 2,
  17         CQ_DESC_TYPE_RQ_ENET = 3,
  18         CQ_DESC_TYPE_RQ_FCP = 4,
  19 };
  20
  21 /* Completion queue descriptor: 16B
  22  *
  23  * All completion queues have this basic layout.  The
  24  * type_specfic area is unique for each completion
  25  * queue type.
  26  */
  27 struct cq_desc {
  28         __le16 completed_index;
  29         __le16 q_number;
  30         u8 type_specfic[11];
  31         u8 type_color;
  32 };
  33
  34 #define CQ_DESC_TYPE_BITS        4
  35 #define CQ_DESC_TYPE_MASK        ((1 << CQ_DESC_TYPE_BITS) - 1)
  36 #define CQ_DESC_COLOR_MASK       1
  37 #define CQ_DESC_COLOR_SHIFT      7
  38 #define CQ_DESC_Q_NUM_BITS       10
  39 #define CQ_DESC_Q_NUM_MASK       ((1 << CQ_DESC_Q_NUM_BITS) - 1)
  40 #define CQ_DESC_COMP_NDX_BITS    12
  41 #define CQ_DESC_COMP_NDX_MASK    ((1 << CQ_DESC_COMP_NDX_BITS) - 1)
  42
  43 static inline void cq_desc_dec(const struct cq_desc *desc_arg,
  44         u8 *type, u8 *color, u16 *q_number, u16 *completed_index)
  45 {
  46         const struct cq_desc *desc = desc_arg;
  47         const u8 type_color = desc->type_color;
  48
  49         *color = (type_color >> CQ_DESC_COLOR_SHIFT) & CQ_DESC_COLOR_MASK;
  50
  51         /*
  52          * Make sure color bit is read from desc *before* other fields
  53          * are read from desc.  Hardware guarantees color bit is last
  54          * bit (byte) written.  Adding the rmb() prevents the compiler
  55          * and/or CPU from reordering the reads which would potentially
  56          * result in reading stale values.
  57          */
  58
  59         rmb();
  60
  61         *type = type_color & CQ_DESC_TYPE_MASK;
  62         *q_number = le16_to_cpu(desc->q_number) & CQ_DESC_Q_NUM_MASK;
  63         *completed_index = le16_to_cpu(desc->completed_index) &
  64                 CQ_DESC_COMP_NDX_MASK;
  65 }
  66
  67 #endif /* _CQ_DESC_H_ */