drivers/net/ethernet/amazon/ena/ena_eth_com.c

   1 /*
   2  * Copyright 2015 Amazon.com, Inc. or its affiliates.
   3  *
   4  * This software is available to you under a choice of one of two
   5  * licenses.  You may choose to be licensed under the terms of the GNU
   6  * General Public License (GPL) Version 2, available from the file
   7  * COPYING in the main directory of this source tree, or the
   8  * BSD license below:
   9  *
  10  *     Redistribution and use in source and binary forms, with or
  11  *     without modification, are permitted provided that the following
  12  *     conditions are met:
  13  *
  14  *      - Redistributions of source code must retain the above
  15  *        copyright notice, this list of conditions and the following
  16  *        disclaimer.
  17  *
  18  *      - Redistributions in binary form must reproduce the above
  19  *        copyright notice, this list of conditions and the following
  20  *        disclaimer in the documentation and/or other materials
  21  *        provided with the distribution.
  22  *
  23  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  27  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  28  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  29  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  30  * SOFTWARE.
  31  */
  32
  33 #include "ena_eth_com.h"
  34
  35 static inline struct ena_eth_io_rx_cdesc_base *ena_com_get_next_rx_cdesc(
  36         struct ena_com_io_cq *io_cq)
  37 {
  38         struct ena_eth_io_rx_cdesc_base *cdesc;
  39         u16 expected_phase, head_masked;
  40         u16 desc_phase;
  41
  42         head_masked = io_cq->head & (io_cq->q_depth - 1);
  43         expected_phase = io_cq->phase;
  44
  45         cdesc = (struct ena_eth_io_rx_cdesc_base *)(io_cq->cdesc_addr.virt_addr
  46                         + (head_masked * io_cq->cdesc_entry_size_in_bytes));
  47
  48         desc_phase = (READ_ONCE(cdesc->status) & ENA_ETH_IO_RX_CDESC_BASE_PHASE_MASK) >>
  49                         ENA_ETH_IO_RX_CDESC_BASE_PHASE_SHIFT;
  50
  51         if (desc_phase != expected_phase)
  52                 return NULL;
  53
  54         return cdesc;
  55 }
  56
  57 static inline void ena_com_cq_inc_head(struct ena_com_io_cq *io_cq)
  58 {
  59         io_cq->head++;
  60
  61         /* Switch phase bit in case of wrap around */
  62         if (unlikely((io_cq->head & (io_cq->q_depth - 1)) == 0))
  63                 io_cq->phase ^= 1;
  64 }
  65
  66 static inline void *get_sq_desc(struct ena_com_io_sq *io_sq)
  67 {
  68         u16 tail_masked;
  69         u32 offset;
  70
  71         tail_masked = io_sq->tail & (io_sq->q_depth - 1);
  72
  73         offset = tail_masked * io_sq->desc_entry_size;
  74
  75         return (void *)((uintptr_t)io_sq->desc_addr.virt_addr + offset);
  76 }
  77
  78 static inline void ena_com_copy_curr_sq_desc_to_dev(struct ena_com_io_sq *io_sq)
  79 {
  80         u16 tail_masked = io_sq->tail & (io_sq->q_depth - 1);
  81         u32 offset = tail_masked * io_sq->desc_entry_size;
  82
  83         /* In case this queue isn't a LLQ */
  84         if (io_sq->mem_queue_type == ENA_ADMIN_PLACEMENT_POLICY_HOST)
  85                 return;
  86
  87         memcpy_toio(io_sq->desc_addr.pbuf_dev_addr + offset,
  88                     io_sq->desc_addr.virt_addr + offset,
  89                     io_sq->desc_entry_size);
  90 }
  91
  92 static inline void ena_com_sq_update_tail(struct ena_com_io_sq *io_sq)
  93 {
  94         io_sq->tail++;
  95
  96         /* Switch phase bit in case of wrap around */
  97         if (unlikely((io_sq->tail & (io_sq->q_depth - 1)) == 0))
  98                 io_sq->phase ^= 1;
  99 }
 100
 101 static inline int ena_com_write_header(struct ena_com_io_sq *io_sq,
 102                                        u8 *head_src, u16 header_len)
 103 {
 104         u16 tail_masked = io_sq->tail & (io_sq->q_depth - 1);
 105         u8 __iomem *dev_head_addr =
 106                 io_sq->header_addr + (tail_masked * io_sq->tx_max_header_size);
 107
 108         if (io_sq->mem_queue_type == ENA_ADMIN_PLACEMENT_POLICY_HOST)
 109                 return 0;
 110
 111         if (unlikely(!io_sq->header_addr)) {
 112                 pr_err("Push buffer header ptr is NULL\n");
 113                 return -EINVAL;
 114         }
 115
 116         memcpy_toio(dev_head_addr, head_src, header_len);
 117
 118         return 0;
 119 }
 120
 121 static inline struct ena_eth_io_rx_cdesc_base *
 122         ena_com_rx_cdesc_idx_to_ptr(struct ena_com_io_cq *io_cq, u16 idx)
 123 {
 124         idx &= (io_cq->q_depth - 1);
 125         return (struct ena_eth_io_rx_cdesc_base *)
 126                 ((uintptr_t)io_cq->cdesc_addr.virt_addr +
 127                 idx * io_cq->cdesc_entry_size_in_bytes);
 128 }
 129
 130 static inline u16 ena_com_cdesc_rx_pkt_get(struct ena_com_io_cq *io_cq,
 131                                            u16 *first_cdesc_idx)
 132 {
 133         struct ena_eth_io_rx_cdesc_base *cdesc;
 134         u16 count = 0, head_masked;
 135         u32 last = 0;
 136
 137         do {
 138                 cdesc = ena_com_get_next_rx_cdesc(io_cq);
 139                 if (!cdesc)
 140                         break;
 141
 142                 ena_com_cq_inc_head(io_cq);
 143                 count++;
 144                 last = (READ_ONCE(cdesc->status) & ENA_ETH_IO_RX_CDESC_BASE_LAST_MASK) >>
 145                         ENA_ETH_IO_RX_CDESC_BASE_LAST_SHIFT;
 146         } while (!last);
 147
 148         if (last) {
 149                 *first_cdesc_idx = io_cq->cur_rx_pkt_cdesc_start_idx;
 150                 count += io_cq->cur_rx_pkt_cdesc_count;
 151
 152                 head_masked = io_cq->head & (io_cq->q_depth - 1);
 153
 154                 io_cq->cur_rx_pkt_cdesc_count = 0;
 155                 io_cq->cur_rx_pkt_cdesc_start_idx = head_masked;
 156
 157                 pr_debug("ena q_id: %d packets were completed. first desc idx %u descs# %d\n",
 158                          io_cq->qid, *first_cdesc_idx, count);
 159         } else {
 160                 io_cq->cur_rx_pkt_cdesc_count += count;
 161                 count = 0;
 162         }
 163
 164         return count;
 165 }
 166
 167 static inline bool ena_com_meta_desc_changed(struct ena_com_io_sq *io_sq,
 168                                              struct ena_com_tx_ctx *ena_tx_ctx)
 169 {
 170         int rc;
 171
 172         if (ena_tx_ctx->meta_valid) {
 173                 rc = memcmp(&io_sq->cached_tx_meta,
 174                             &ena_tx_ctx->ena_meta,
 175                             sizeof(struct ena_com_tx_meta));
 176
 177                 if (unlikely(rc != 0))
 178                         return true;
 179         }
 180
 181         return false;
 182 }
 183
 184 static inline void ena_com_create_and_store_tx_meta_desc(struct ena_com_io_sq *io_sq,
 185                                                          struct ena_com_tx_ctx *ena_tx_ctx)
 186 {
 187         struct ena_eth_io_tx_meta_desc *meta_desc = NULL;
 188         struct ena_com_tx_meta *ena_meta = &ena_tx_ctx->ena_meta;
 189
 190         meta_desc = get_sq_desc(io_sq);
 191         memset(meta_desc, 0x0, sizeof(struct ena_eth_io_tx_meta_desc));
 192
 193         meta_desc->len_ctrl |= ENA_ETH_IO_TX_META_DESC_META_DESC_MASK;
 194
 195         meta_desc->len_ctrl |= ENA_ETH_IO_TX_META_DESC_EXT_VALID_MASK;
 196
 197         /* bits 0-9 of the mss */
 198         meta_desc->word2 |= (ena_meta->mss <<
 199                 ENA_ETH_IO_TX_META_DESC_MSS_LO_SHIFT) &
 200                 ENA_ETH_IO_TX_META_DESC_MSS_LO_MASK;
 201         /* bits 10-13 of the mss */
 202         meta_desc->len_ctrl |= ((ena_meta->mss >> 10) <<
 203                 ENA_ETH_IO_TX_META_DESC_MSS_HI_SHIFT) &
 204                 ENA_ETH_IO_TX_META_DESC_MSS_HI_MASK;
 205
 206         /* Extended meta desc */
 207         meta_desc->len_ctrl |= ENA_ETH_IO_TX_META_DESC_ETH_META_TYPE_MASK;
 208         meta_desc->len_ctrl |= ENA_ETH_IO_TX_META_DESC_META_STORE_MASK;
 209         meta_desc->len_ctrl |= (io_sq->phase <<
 210                 ENA_ETH_IO_TX_META_DESC_PHASE_SHIFT) &
 211                 ENA_ETH_IO_TX_META_DESC_PHASE_MASK;
 212
 213         meta_desc->len_ctrl |= ENA_ETH_IO_TX_META_DESC_FIRST_MASK;
 214         meta_desc->word2 |= ena_meta->l3_hdr_len &
 215                 ENA_ETH_IO_TX_META_DESC_L3_HDR_LEN_MASK;
 216         meta_desc->word2 |= (ena_meta->l3_hdr_offset <<
 217                 ENA_ETH_IO_TX_META_DESC_L3_HDR_OFF_SHIFT) &
 218                 ENA_ETH_IO_TX_META_DESC_L3_HDR_OFF_MASK;
 219
 220         meta_desc->word2 |= (ena_meta->l4_hdr_len <<
 221                 ENA_ETH_IO_TX_META_DESC_L4_HDR_LEN_IN_WORDS_SHIFT) &
 222                 ENA_ETH_IO_TX_META_DESC_L4_HDR_LEN_IN_WORDS_MASK;
 223
 224         meta_desc->len_ctrl |= ENA_ETH_IO_TX_META_DESC_META_STORE_MASK;
 225
 226         /* Cached the meta desc */
 227         memcpy(&io_sq->cached_tx_meta, ena_meta,
 228                sizeof(struct ena_com_tx_meta));
 229
 230         ena_com_copy_curr_sq_desc_to_dev(io_sq);
 231         ena_com_sq_update_tail(io_sq);
 232 }
 233
 234 static inline void ena_com_rx_set_flags(struct ena_com_rx_ctx *ena_rx_ctx,
 235                                         struct ena_eth_io_rx_cdesc_base *cdesc)
 236 {
 237         ena_rx_ctx->l3_proto = cdesc->status &
 238                 ENA_ETH_IO_RX_CDESC_BASE_L3_PROTO_IDX_MASK;
 239         ena_rx_ctx->l4_proto =
 240                 (cdesc->status & ENA_ETH_IO_RX_CDESC_BASE_L4_PROTO_IDX_MASK) >>
 241                 ENA_ETH_IO_RX_CDESC_BASE_L4_PROTO_IDX_SHIFT;
 242         ena_rx_ctx->l3_csum_err =
 243                 (cdesc->status & ENA_ETH_IO_RX_CDESC_BASE_L3_CSUM_ERR_MASK) >>
 244                 ENA_ETH_IO_RX_CDESC_BASE_L3_CSUM_ERR_SHIFT;
 245         ena_rx_ctx->l4_csum_err =
 246                 (cdesc->status & ENA_ETH_IO_RX_CDESC_BASE_L4_CSUM_ERR_MASK) >>
 247                 ENA_ETH_IO_RX_CDESC_BASE_L4_CSUM_ERR_SHIFT;
 248         ena_rx_ctx->hash = cdesc->hash;
 249         ena_rx_ctx->frag =
 250                 (cdesc->status & ENA_ETH_IO_RX_CDESC_BASE_IPV4_FRAG_MASK) >>
 251                 ENA_ETH_IO_RX_CDESC_BASE_IPV4_FRAG_SHIFT;
 252
 253         pr_debug("ena_rx_ctx->l3_proto %d ena_rx_ctx->l4_proto %d\nena_rx_ctx->l3_csum_err %d ena_rx_ctx->l4_csum_err %d\nhash frag %d frag: %d cdesc_status: %x\n",
 254                  ena_rx_ctx->l3_proto, ena_rx_ctx->l4_proto,
 255                  ena_rx_ctx->l3_csum_err, ena_rx_ctx->l4_csum_err,
 256                  ena_rx_ctx->hash, ena_rx_ctx->frag, cdesc->status);
 257 }
 258
 259 /*****************************************************************************/
 260 /*****************************     API      **********************************/
 261 /*****************************************************************************/
 262
 263 int ena_com_prepare_tx(struct ena_com_io_sq *io_sq,
 264                        struct ena_com_tx_ctx *ena_tx_ctx,
 265                        int *nb_hw_desc)
 266 {
 267         struct ena_eth_io_tx_desc *desc = NULL;
 268         struct ena_com_buf *ena_bufs = ena_tx_ctx->ena_bufs;
 269         void *push_header = ena_tx_ctx->push_header;
 270         u16 header_len = ena_tx_ctx->header_len;
 271         u16 num_bufs = ena_tx_ctx->num_bufs;
 272         int total_desc, i, rc;
 273         bool have_meta;
 274         u64 addr_hi;
 275
 276         WARN(io_sq->direction != ENA_COM_IO_QUEUE_DIRECTION_TX, "wrong Q type");
 277
 278         /* num_bufs +1 for potential meta desc */
 279         if (ena_com_sq_empty_space(io_sq) < (num_bufs + 1)) {
 280                 pr_err("Not enough space in the tx queue\n");
 281                 return -ENOMEM;
 282         }
 283
 284         if (unlikely(header_len > io_sq->tx_max_header_size)) {
 285                 pr_err("header size is too large %d max header: %d\n",
 286                        header_len, io_sq->tx_max_header_size);
 287                 return -EINVAL;
 288         }
 289
 290         /* start with pushing the header (if needed) */
 291         rc = ena_com_write_header(io_sq, push_header, header_len);
 292         if (unlikely(rc))
 293                 return rc;
 294
 295         have_meta = ena_tx_ctx->meta_valid && ena_com_meta_desc_changed(io_sq,
 296                         ena_tx_ctx);
 297         if (have_meta)
 298                 ena_com_create_and_store_tx_meta_desc(io_sq, ena_tx_ctx);
 299
 300         /* If the caller doesn't want send packets */
 301         if (unlikely(!num_bufs && !header_len)) {
 302                 *nb_hw_desc = have_meta ? 0 : 1;
 303                 return 0;
 304         }
 305
 306         desc = get_sq_desc(io_sq);
 307         memset(desc, 0x0, sizeof(struct ena_eth_io_tx_desc));
 308
 309         /* Set first desc when we don't have meta descriptor */
 310         if (!have_meta)
 311                 desc->len_ctrl |= ENA_ETH_IO_TX_DESC_FIRST_MASK;
 312
 313         desc->buff_addr_hi_hdr_sz |= (header_len <<
 314                 ENA_ETH_IO_TX_DESC_HEADER_LENGTH_SHIFT) &
 315                 ENA_ETH_IO_TX_DESC_HEADER_LENGTH_MASK;
 316         desc->len_ctrl |= (io_sq->phase << ENA_ETH_IO_TX_DESC_PHASE_SHIFT) &
 317                 ENA_ETH_IO_TX_DESC_PHASE_MASK;
 318
 319         desc->len_ctrl |= ENA_ETH_IO_TX_DESC_COMP_REQ_MASK;
 320
 321         /* Bits 0-9 */
 322         desc->meta_ctrl |= (ena_tx_ctx->req_id <<
 323                 ENA_ETH_IO_TX_DESC_REQ_ID_LO_SHIFT) &
 324                 ENA_ETH_IO_TX_DESC_REQ_ID_LO_MASK;
 325
 326         desc->meta_ctrl |= (ena_tx_ctx->df <<
 327                 ENA_ETH_IO_TX_DESC_DF_SHIFT) &
 328                 ENA_ETH_IO_TX_DESC_DF_MASK;
 329
 330         /* Bits 10-15 */
 331         desc->len_ctrl |= ((ena_tx_ctx->req_id >> 10) <<
 332                 ENA_ETH_IO_TX_DESC_REQ_ID_HI_SHIFT) &
 333                 ENA_ETH_IO_TX_DESC_REQ_ID_HI_MASK;
 334
 335         if (ena_tx_ctx->meta_valid) {
 336                 desc->meta_ctrl |= (ena_tx_ctx->tso_enable <<
 337                         ENA_ETH_IO_TX_DESC_TSO_EN_SHIFT) &
 338                         ENA_ETH_IO_TX_DESC_TSO_EN_MASK;
 339                 desc->meta_ctrl |= ena_tx_ctx->l3_proto &
 340                         ENA_ETH_IO_TX_DESC_L3_PROTO_IDX_MASK;
 341                 desc->meta_ctrl |= (ena_tx_ctx->l4_proto <<
 342                         ENA_ETH_IO_TX_DESC_L4_PROTO_IDX_SHIFT) &
 343                         ENA_ETH_IO_TX_DESC_L4_PROTO_IDX_MASK;
 344                 desc->meta_ctrl |= (ena_tx_ctx->l3_csum_enable <<
 345                         ENA_ETH_IO_TX_DESC_L3_CSUM_EN_SHIFT) &
 346                         ENA_ETH_IO_TX_DESC_L3_CSUM_EN_MASK;
 347                 desc->meta_ctrl |= (ena_tx_ctx->l4_csum_enable <<
 348                         ENA_ETH_IO_TX_DESC_L4_CSUM_EN_SHIFT) &
 349                         ENA_ETH_IO_TX_DESC_L4_CSUM_EN_MASK;
 350                 desc->meta_ctrl |= (ena_tx_ctx->l4_csum_partial <<
 351                         ENA_ETH_IO_TX_DESC_L4_CSUM_PARTIAL_SHIFT) &
 352                         ENA_ETH_IO_TX_DESC_L4_CSUM_PARTIAL_MASK;
 353         }
 354
 355         for (i = 0; i < num_bufs; i++) {
 356                 /* The first desc share the same desc as the header */
 357                 if (likely(i != 0)) {
 358                         ena_com_copy_curr_sq_desc_to_dev(io_sq);
 359                         ena_com_sq_update_tail(io_sq);
 360
 361                         desc = get_sq_desc(io_sq);
 362                         memset(desc, 0x0, sizeof(struct ena_eth_io_tx_desc));
 363
 364                         desc->len_ctrl |= (io_sq->phase <<
 365                                 ENA_ETH_IO_TX_DESC_PHASE_SHIFT) &
 366                                 ENA_ETH_IO_TX_DESC_PHASE_MASK;
 367                 }
 368
 369                 desc->len_ctrl |= ena_bufs->len &
 370                         ENA_ETH_IO_TX_DESC_LENGTH_MASK;
 371
 372                 addr_hi = ((ena_bufs->paddr &
 373                         GENMASK_ULL(io_sq->dma_addr_bits - 1, 32)) >> 32);
 374
 375                 desc->buff_addr_lo = (u32)ena_bufs->paddr;
 376                 desc->buff_addr_hi_hdr_sz |= addr_hi &
 377                         ENA_ETH_IO_TX_DESC_ADDR_HI_MASK;
 378                 ena_bufs++;
 379         }
 380
 381         /* set the last desc indicator */
 382         desc->len_ctrl |= ENA_ETH_IO_TX_DESC_LAST_MASK;
 383
 384         ena_com_copy_curr_sq_desc_to_dev(io_sq);
 385
 386         ena_com_sq_update_tail(io_sq);
 387
 388         total_desc = max_t(u16, num_bufs, 1);
 389         total_desc += have_meta ? 1 : 0;
 390
 391         *nb_hw_desc = total_desc;
 392         return 0;
 393 }
 394
 395 int ena_com_rx_pkt(struct ena_com_io_cq *io_cq,
 396                    struct ena_com_io_sq *io_sq,
 397                    struct ena_com_rx_ctx *ena_rx_ctx)
 398 {
 399         struct ena_com_rx_buf_info *ena_buf = &ena_rx_ctx->ena_bufs[0];
 400         struct ena_eth_io_rx_cdesc_base *cdesc = NULL;
 401         u16 cdesc_idx = 0;
 402         u16 nb_hw_desc;
 403         u16 i;
 404
 405         WARN(io_cq->direction != ENA_COM_IO_QUEUE_DIRECTION_RX, "wrong Q type");
 406
 407         nb_hw_desc = ena_com_cdesc_rx_pkt_get(io_cq, &cdesc_idx);
 408         if (nb_hw_desc == 0) {
 409                 ena_rx_ctx->descs = nb_hw_desc;
 410                 return 0;
 411         }
 412
 413         pr_debug("fetch rx packet: queue %d completed desc: %d\n", io_cq->qid,
 414                  nb_hw_desc);
 415
 416         if (unlikely(nb_hw_desc > ena_rx_ctx->max_bufs)) {
 417                 pr_err("Too many RX cdescs (%d) > MAX(%d)\n", nb_hw_desc,
 418                        ena_rx_ctx->max_bufs);
 419                 return -ENOSPC;
 420         }
 421
 422         for (i = 0; i < nb_hw_desc; i++) {
 423                 cdesc = ena_com_rx_cdesc_idx_to_ptr(io_cq, cdesc_idx + i);
 424
 425                 ena_buf->len = cdesc->length;
 426                 ena_buf->req_id = cdesc->req_id;
 427                 ena_buf++;
 428         }
 429
 430         /* Update SQ head ptr */
 431         io_sq->next_to_comp += nb_hw_desc;
 432
 433         pr_debug("[%s][QID#%d] Updating SQ head to: %d\n", __func__, io_sq->qid,
 434                  io_sq->next_to_comp);
 435
 436         /* Get rx flags from the last pkt */
 437         ena_com_rx_set_flags(ena_rx_ctx, cdesc);
 438
 439         ena_rx_ctx->descs = nb_hw_desc;
 440         return 0;
 441 }
 442
 443 int ena_com_add_single_rx_desc(struct ena_com_io_sq *io_sq,
 444                                struct ena_com_buf *ena_buf,
 445                                u16 req_id)
 446 {
 447         struct ena_eth_io_rx_desc *desc;
 448
 449         WARN(io_sq->direction != ENA_COM_IO_QUEUE_DIRECTION_RX, "wrong Q type");
 450
 451         if (unlikely(ena_com_sq_empty_space(io_sq) == 0))
 452                 return -ENOSPC;
 453
 454         desc = get_sq_desc(io_sq);
 455         memset(desc, 0x0, sizeof(struct ena_eth_io_rx_desc));
 456
 457         desc->length = ena_buf->len;
 458
 459         desc->ctrl |= ENA_ETH_IO_RX_DESC_FIRST_MASK;
 460         desc->ctrl |= ENA_ETH_IO_RX_DESC_LAST_MASK;
 461         desc->ctrl |= io_sq->phase & ENA_ETH_IO_RX_DESC_PHASE_MASK;
 462         desc->ctrl |= ENA_ETH_IO_RX_DESC_COMP_REQ_MASK;
 463
 464         desc->req_id = req_id;
 465
 466         desc->buff_addr_lo = (u32)ena_buf->paddr;
 467         desc->buff_addr_hi =
 468                 ((ena_buf->paddr & GENMASK_ULL(io_sq->dma_addr_bits - 1, 32)) >> 32);
 469
 470         ena_com_sq_update_tail(io_sq);
 471
 472         return 0;
 473 }
 474
 475 int ena_com_tx_comp_req_id_get(struct ena_com_io_cq *io_cq, u16 *req_id)
 476 {
 477         u8 expected_phase, cdesc_phase;
 478         struct ena_eth_io_tx_cdesc *cdesc;
 479         u16 masked_head;
 480
 481         masked_head = io_cq->head & (io_cq->q_depth - 1);
 482         expected_phase = io_cq->phase;
 483
 484         cdesc = (struct ena_eth_io_tx_cdesc *)
 485                 ((uintptr_t)io_cq->cdesc_addr.virt_addr +
 486                 (masked_head * io_cq->cdesc_entry_size_in_bytes));
 487
 488         /* When the current completion descriptor phase isn't the same as the
 489          * expected, it mean that the device still didn't update
 490          * this completion.
 491          */
 492         cdesc_phase = READ_ONCE(cdesc->flags) & ENA_ETH_IO_TX_CDESC_PHASE_MASK;
 493         if (cdesc_phase != expected_phase)
 494                 return -EAGAIN;
 495
 496         ena_com_cq_inc_head(io_cq);
 497
 498         *req_id = READ_ONCE(cdesc->req_id);
 499
 500         return 0;
 501 }