drivers/scsi/snic/cq_desc.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /* Copyright 2014 Cisco Systems, Inc.  All rights reserved. */
   3
   4 #ifndef _CQ_DESC_H_
   5 #define _CQ_DESC_H_
   6
   7 /*
   8  * Completion queue descriptor types
   9  */
  10 enum cq_desc_types {
  11         CQ_DESC_TYPE_WQ_ENET = 0,
  12         CQ_DESC_TYPE_DESC_COPY = 1,
  13         CQ_DESC_TYPE_WQ_EXCH = 2,
  14         CQ_DESC_TYPE_RQ_ENET = 3,
  15         CQ_DESC_TYPE_RQ_FCP = 4,
  16 };
  17
  18 /* Completion queue descriptor: 16B
  19  *
  20  * All completion queues have this basic layout.  The
  21  * type_specific area is unique for each completion
  22  * queue type.
  23  */
  24 struct cq_desc {
  25         __le16 completed_index;
  26         __le16 q_number;
  27         u8 type_specific[11];
  28         u8 type_color;
  29 };
  30
  31 #define CQ_DESC_TYPE_BITS        4
  32 #define CQ_DESC_TYPE_MASK        ((1 << CQ_DESC_TYPE_BITS) - 1)
  33 #define CQ_DESC_COLOR_MASK       1
  34 #define CQ_DESC_COLOR_SHIFT      7
  35 #define CQ_DESC_Q_NUM_BITS       10
  36 #define CQ_DESC_Q_NUM_MASK       ((1 << CQ_DESC_Q_NUM_BITS) - 1)
  37 #define CQ_DESC_COMP_NDX_BITS    12
  38 #define CQ_DESC_COMP_NDX_MASK    ((1 << CQ_DESC_COMP_NDX_BITS) - 1)
  39
  40 static inline void cq_desc_dec(const struct cq_desc *desc_arg,
  41         u8 *type, u8 *color, u16 *q_number, u16 *completed_index)
  42 {
  43         const struct cq_desc *desc = desc_arg;
  44         const u8 type_color = desc->type_color;
  45
  46         *color = (type_color >> CQ_DESC_COLOR_SHIFT) & CQ_DESC_COLOR_MASK;
  47
  48         /*
  49          * Make sure color bit is read from desc *before* other fields
  50          * are read from desc.  Hardware guarantees color bit is last
  51          * bit (byte) written.  Adding the rmb() prevents the compiler
  52          * and/or CPU from reordering the reads which would potentially
  53          * result in reading stale values.
  54          */
  55         rmb();
  56
  57         *type = type_color & CQ_DESC_TYPE_MASK;
  58         *q_number = le16_to_cpu(desc->q_number) & CQ_DESC_Q_NUM_MASK;
  59         *completed_index = le16_to_cpu(desc->completed_index) &
  60                 CQ_DESC_COMP_NDX_MASK;
  61 }
  62
  63 #endif /* _CQ_DESC_H_ */