drivers/net/sfc/tx.c

   1 /****************************************************************************
   2  * Driver for Solarflare Solarstorm network controllers and boards
   3  * Copyright 2005-2006 Fen Systems Ltd.
   4  * Copyright 2005-2008 Solarflare Communications Inc.
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 as published
   8  * by the Free Software Foundation, incorporated herein by reference.
   9  */
  10
  11 #include <linux/pci.h>
  12 #include <linux/tcp.h>
  13 #include <linux/ip.h>
  14 #include <linux/in.h>
  15 #include <linux/if_ether.h>
  16 #include <linux/highmem.h>
  17 #include "net_driver.h"
  18 #include "tx.h"
  19 #include "efx.h"
  20 #include "falcon.h"
  21 #include "workarounds.h"
  22
  23 /*
  24  * TX descriptor ring full threshold
  25  *
  26  * The tx_queue descriptor ring fill-level must fall below this value
  27  * before we restart the netif queue
  28  */
  29 #define EFX_NETDEV_TX_THRESHOLD(_tx_queue)      \
  30         (_tx_queue->efx->type->txd_ring_mask / 2u)
  31
  32 /* We want to be able to nest calls to netif_stop_queue(), since each
  33  * channel can have an individual stop on the queue.
  34  */
  35 void efx_stop_queue(struct efx_nic *efx)
  36 {
  37         spin_lock_bh(&efx->netif_stop_lock);
  38         EFX_TRACE(efx, "stop TX queue\n");
  39
  40         atomic_inc(&efx->netif_stop_count);
  41         netif_stop_queue(efx->net_dev);
  42
  43         spin_unlock_bh(&efx->netif_stop_lock);
  44 }
  45
  46 /* Wake netif's TX queue
  47  * We want to be able to nest calls to netif_stop_queue(), since each
  48  * channel can have an individual stop on the queue.
  49  */
  50 inline void efx_wake_queue(struct efx_nic *efx)
  51 {
  52         local_bh_disable();
  53         if (atomic_dec_and_lock(&efx->netif_stop_count,
  54                                 &efx->netif_stop_lock)) {
  55                 EFX_TRACE(efx, "waking TX queue\n");
  56                 netif_wake_queue(efx->net_dev);
  57                 spin_unlock(&efx->netif_stop_lock);
  58         }
  59         local_bh_enable();
  60 }
  61
  62 static inline void efx_dequeue_buffer(struct efx_tx_queue *tx_queue,
  63                                       struct efx_tx_buffer *buffer)
  64 {
  65         if (buffer->unmap_len) {
  66                 struct pci_dev *pci_dev = tx_queue->efx->pci_dev;
  67                 if (buffer->unmap_single)
  68                         pci_unmap_single(pci_dev, buffer->unmap_addr,
  69                                          buffer->unmap_len, PCI_DMA_TODEVICE);
  70                 else
  71                         pci_unmap_page(pci_dev, buffer->unmap_addr,
  72                                        buffer->unmap_len, PCI_DMA_TODEVICE);
  73                 buffer->unmap_len = 0;
  74                 buffer->unmap_single = 0;
  75         }
  76
  77         if (buffer->skb) {
  78                 dev_kfree_skb_any((struct sk_buff *) buffer->skb);
  79                 buffer->skb = NULL;
  80                 EFX_TRACE(tx_queue->efx, "TX queue %d transmission id %x "
  81                           "complete\n", tx_queue->queue, read_ptr);
  82         }
  83 }
  84
  85
  86 /*
  87  * Add a socket buffer to a TX queue
  88  *
  89  * This maps all fragments of a socket buffer for DMA and adds them to
  90  * the TX queue.  The queue's insert pointer will be incremented by
  91  * the number of fragments in the socket buffer.
  92  *
  93  * If any DMA mapping fails, any mapped fragments will be unmapped,
  94  * the queue's insert pointer will be restored to its original value.
  95  *
  96  * Returns NETDEV_TX_OK or NETDEV_TX_BUSY
  97  * You must hold netif_tx_lock() to call this function.
  98  */
  99 static inline int efx_enqueue_skb(struct efx_tx_queue *tx_queue,
 100                                   const struct sk_buff *skb)
 101 {
 102         struct efx_nic *efx = tx_queue->efx;
 103         struct pci_dev *pci_dev = efx->pci_dev;
 104         struct efx_tx_buffer *buffer;
 105         skb_frag_t *fragment;
 106         struct page *page;
 107         int page_offset;
 108         unsigned int len, unmap_len = 0, fill_level, insert_ptr, misalign;
 109         dma_addr_t dma_addr, unmap_addr = 0;
 110         unsigned int dma_len;
 111         unsigned unmap_single;
 112         int q_space, i = 0;
 113         int rc = NETDEV_TX_OK;
 114
 115         EFX_BUG_ON_PARANOID(tx_queue->write_count != tx_queue->insert_count);
 116
 117         /* Get size of the initial fragment */
 118         len = skb_headlen(skb);
 119
 120         fill_level = tx_queue->insert_count - tx_queue->old_read_count;
 121         q_space = efx->type->txd_ring_mask - 1 - fill_level;
 122
 123         /* Map for DMA.  Use pci_map_single rather than pci_map_page
 124          * since this is more efficient on machines with sparse
 125          * memory.
 126          */
 127         unmap_single = 1;
 128         dma_addr = pci_map_single(pci_dev, skb->data, len, PCI_DMA_TODEVICE);
 129
 130         /* Process all fragments */
 131         while (1) {
 132                 if (unlikely(pci_dma_mapping_error(dma_addr)))
 133                         goto pci_err;
 134
 135                 /* Store fields for marking in the per-fragment final
 136                  * descriptor */
 137                 unmap_len = len;
 138                 unmap_addr = dma_addr;
 139
 140                 /* Add to TX queue, splitting across DMA boundaries */
 141                 do {
 142                         if (unlikely(q_space-- <= 0)) {
 143                                 /* It might be that completions have
 144                                  * happened since the xmit path last
 145                                  * checked.  Update the xmit path's
 146                                  * copy of read_count.
 147                                  */
 148                                 ++tx_queue->stopped;
 149                                 /* This memory barrier protects the
 150                                  * change of stopped from the access
 151                                  * of read_count. */
 152                                 smp_mb();
 153                                 tx_queue->old_read_count =
 154                                         *(volatile unsigned *)
 155                                         &tx_queue->read_count;
 156                                 fill_level = (tx_queue->insert_count
 157                                               - tx_queue->old_read_count);
 158                                 q_space = (efx->type->txd_ring_mask - 1 -
 159                                            fill_level);
 160                                 if (unlikely(q_space-- <= 0))
 161                                         goto stop;
 162                                 smp_mb();
 163                                 --tx_queue->stopped;
 164                         }
 165
 166                         insert_ptr = (tx_queue->insert_count &
 167                                       efx->type->txd_ring_mask);
 168                         buffer = &tx_queue->buffer[insert_ptr];
 169                         EFX_BUG_ON_PARANOID(buffer->skb);
 170                         EFX_BUG_ON_PARANOID(buffer->len);
 171                         EFX_BUG_ON_PARANOID(buffer->continuation != 1);
 172                         EFX_BUG_ON_PARANOID(buffer->unmap_len);
 173
 174                         dma_len = (((~dma_addr) & efx->type->tx_dma_mask) + 1);
 175                         if (likely(dma_len > len))
 176                                 dma_len = len;
 177
 178                         misalign = (unsigned)dma_addr & efx->type->bug5391_mask;
 179                         if (misalign && dma_len + misalign > 512)
 180                                 dma_len = 512 - misalign;
 181
 182                         /* Fill out per descriptor fields */
 183                         buffer->len = dma_len;
 184                         buffer->dma_addr = dma_addr;
 185                         len -= dma_len;
 186                         dma_addr += dma_len;
 187                         ++tx_queue->insert_count;
 188                 } while (len);
 189
 190                 /* Transfer ownership of the unmapping to the final buffer */
 191                 buffer->unmap_addr = unmap_addr;
 192                 buffer->unmap_single = unmap_single;
 193                 buffer->unmap_len = unmap_len;
 194                 unmap_len = 0;
 195
 196                 /* Get address and size of next fragment */
 197                 if (i >= skb_shinfo(skb)->nr_frags)
 198                         break;
 199                 fragment = &skb_shinfo(skb)->frags[i];
 200                 len = fragment->size;
 201                 page = fragment->page;
 202                 page_offset = fragment->page_offset;
 203                 i++;
 204                 /* Map for DMA */
 205                 unmap_single = 0;
 206                 dma_addr = pci_map_page(pci_dev, page, page_offset, len,
 207                                         PCI_DMA_TODEVICE);
 208         }
 209
 210         /* Transfer ownership of the skb to the final buffer */
 211         buffer->skb = skb;
 212         buffer->continuation = 0;
 213
 214         /* Pass off to hardware */
 215         falcon_push_buffers(tx_queue);
 216
 217         return NETDEV_TX_OK;
 218
 219  pci_err:
 220         EFX_ERR_RL(efx, " TX queue %d could not map skb with %d bytes %d "
 221                    "fragments for DMA\n", tx_queue->queue, skb->len,
 222                    skb_shinfo(skb)->nr_frags + 1);
 223
 224         /* Mark the packet as transmitted, and free the SKB ourselves */
 225         dev_kfree_skb_any((struct sk_buff *)skb);
 226         goto unwind;
 227
 228  stop:
 229         rc = NETDEV_TX_BUSY;
 230
 231         if (tx_queue->stopped == 1)
 232                 efx_stop_queue(efx);
 233
 234  unwind:
 235         /* Work backwards until we hit the original insert pointer value */
 236         while (tx_queue->insert_count != tx_queue->write_count) {
 237                 --tx_queue->insert_count;
 238                 insert_ptr = tx_queue->insert_count & efx->type->txd_ring_mask;
 239                 buffer = &tx_queue->buffer[insert_ptr];
 240                 efx_dequeue_buffer(tx_queue, buffer);
 241                 buffer->len = 0;
 242         }
 243
 244         /* Free the fragment we were mid-way through pushing */
 245         if (unmap_len)
 246                 pci_unmap_page(pci_dev, unmap_addr, unmap_len,
 247                                PCI_DMA_TODEVICE);
 248
 249         return rc;
 250 }
 251
 252 /* Remove packets from the TX queue
 253  *
 254  * This removes packets from the TX queue, up to and including the
 255  * specified index.
 256  */
 257 static inline void efx_dequeue_buffers(struct efx_tx_queue *tx_queue,
 258                                        unsigned int index)
 259 {
 260         struct efx_nic *efx = tx_queue->efx;
 261         unsigned int stop_index, read_ptr;
 262         unsigned int mask = tx_queue->efx->type->txd_ring_mask;
 263
 264         stop_index = (index + 1) & mask;
 265         read_ptr = tx_queue->read_count & mask;
 266
 267         while (read_ptr != stop_index) {
 268                 struct efx_tx_buffer *buffer = &tx_queue->buffer[read_ptr];
 269                 if (unlikely(buffer->len == 0)) {
 270                         EFX_ERR(tx_queue->efx, "TX queue %d spurious TX "
 271                                 "completion id %x\n", tx_queue->queue,
 272                                 read_ptr);
 273                         efx_schedule_reset(efx, RESET_TYPE_TX_SKIP);
 274                         return;
 275                 }
 276
 277                 efx_dequeue_buffer(tx_queue, buffer);
 278                 buffer->continuation = 1;
 279                 buffer->len = 0;
 280
 281                 ++tx_queue->read_count;
 282                 read_ptr = tx_queue->read_count & mask;
 283         }
 284 }
 285
 286 /* Initiate a packet transmission on the specified TX queue.
 287  * Note that returning anything other than NETDEV_TX_OK will cause the
 288  * OS to free the skb.
 289  *
 290  * This function is split out from efx_hard_start_xmit to allow the
 291  * loopback test to direct packets via specific TX queues.  It is
 292  * therefore a non-static inline, so as not to penalise performance
 293  * for non-loopback transmissions.
 294  *
 295  * Context: netif_tx_lock held
 296  */
 297 inline int efx_xmit(struct efx_nic *efx,
 298                     struct efx_tx_queue *tx_queue, struct sk_buff *skb)
 299 {
 300         int rc;
 301
 302         /* Map fragments for DMA and add to TX queue */
 303         rc = efx_enqueue_skb(tx_queue, skb);
 304         if (unlikely(rc != NETDEV_TX_OK))
 305                 goto out;
 306
 307         /* Update last TX timer */
 308         efx->net_dev->trans_start = jiffies;
 309
 310  out:
 311         return rc;
 312 }
 313
 314 /* Initiate a packet transmission.  We use one channel per CPU
 315  * (sharing when we have more CPUs than channels).  On Falcon, the TX
 316  * completion events will be directed back to the CPU that transmitted
 317  * the packet, which should be cache-efficient.
 318  *
 319  * Context: non-blocking.
 320  * Note that returning anything other than NETDEV_TX_OK will cause the
 321  * OS to free the skb.
 322  */
 323 int efx_hard_start_xmit(struct sk_buff *skb, struct net_device *net_dev)
 324 {
 325         struct efx_nic *efx = net_dev->priv;
 326         return efx_xmit(efx, &efx->tx_queue[0], skb);
 327 }
 328
 329 void efx_xmit_done(struct efx_tx_queue *tx_queue, unsigned int index)
 330 {
 331         unsigned fill_level;
 332         struct efx_nic *efx = tx_queue->efx;
 333
 334         EFX_BUG_ON_PARANOID(index > efx->type->txd_ring_mask);
 335
 336         efx_dequeue_buffers(tx_queue, index);
 337
 338         /* See if we need to restart the netif queue.  This barrier
 339          * separates the update of read_count from the test of
 340          * stopped. */
 341         smp_mb();
 342         if (unlikely(tx_queue->stopped)) {
 343                 fill_level = tx_queue->insert_count - tx_queue->read_count;
 344                 if (fill_level < EFX_NETDEV_TX_THRESHOLD(tx_queue)) {
 345                         EFX_BUG_ON_PARANOID(!NET_DEV_REGISTERED(efx));
 346
 347                         /* Do this under netif_tx_lock(), to avoid racing
 348                          * with efx_xmit(). */
 349                         netif_tx_lock(efx->net_dev);
 350                         if (tx_queue->stopped) {
 351                                 tx_queue->stopped = 0;
 352                                 efx_wake_queue(efx);
 353                         }
 354                         netif_tx_unlock(efx->net_dev);
 355                 }
 356         }
 357 }
 358
 359 int efx_probe_tx_queue(struct efx_tx_queue *tx_queue)
 360 {
 361         struct efx_nic *efx = tx_queue->efx;
 362         unsigned int txq_size;
 363         int i, rc;
 364
 365         EFX_LOG(efx, "creating TX queue %d\n", tx_queue->queue);
 366
 367         /* Allocate software ring */
 368         txq_size = (efx->type->txd_ring_mask + 1) * sizeof(*tx_queue->buffer);
 369         tx_queue->buffer = kzalloc(txq_size, GFP_KERNEL);
 370         if (!tx_queue->buffer) {
 371                 rc = -ENOMEM;
 372                 goto fail1;
 373         }
 374         for (i = 0; i <= efx->type->txd_ring_mask; ++i)
 375                 tx_queue->buffer[i].continuation = 1;
 376
 377         /* Allocate hardware ring */
 378         rc = falcon_probe_tx(tx_queue);
 379         if (rc)
 380                 goto fail2;
 381
 382         return 0;
 383
 384  fail2:
 385         kfree(tx_queue->buffer);
 386         tx_queue->buffer = NULL;
 387  fail1:
 388         tx_queue->used = 0;
 389
 390         return rc;
 391 }
 392
 393 int efx_init_tx_queue(struct efx_tx_queue *tx_queue)
 394 {
 395         EFX_LOG(tx_queue->efx, "initialising TX queue %d\n", tx_queue->queue);
 396
 397         tx_queue->insert_count = 0;
 398         tx_queue->write_count = 0;
 399         tx_queue->read_count = 0;
 400         tx_queue->old_read_count = 0;
 401         BUG_ON(tx_queue->stopped);
 402
 403         /* Set up TX descriptor ring */
 404         return falcon_init_tx(tx_queue);
 405 }
 406
 407 void efx_release_tx_buffers(struct efx_tx_queue *tx_queue)
 408 {
 409         struct efx_tx_buffer *buffer;
 410
 411         if (!tx_queue->buffer)
 412                 return;
 413
 414         /* Free any buffers left in the ring */
 415         while (tx_queue->read_count != tx_queue->write_count) {
 416                 buffer = &tx_queue->buffer[tx_queue->read_count &
 417                                            tx_queue->efx->type->txd_ring_mask];
 418                 efx_dequeue_buffer(tx_queue, buffer);
 419                 buffer->continuation = 1;
 420                 buffer->len = 0;
 421
 422                 ++tx_queue->read_count;
 423         }
 424 }
 425
 426 void efx_fini_tx_queue(struct efx_tx_queue *tx_queue)
 427 {
 428         EFX_LOG(tx_queue->efx, "shutting down TX queue %d\n", tx_queue->queue);
 429
 430         /* Flush TX queue, remove descriptor ring */
 431         falcon_fini_tx(tx_queue);
 432
 433         efx_release_tx_buffers(tx_queue);
 434
 435         /* Release queue's stop on port, if any */
 436         if (tx_queue->stopped) {
 437                 tx_queue->stopped = 0;
 438                 efx_wake_queue(tx_queue->efx);
 439         }
 440 }
 441
 442 void efx_remove_tx_queue(struct efx_tx_queue *tx_queue)
 443 {
 444         EFX_LOG(tx_queue->efx, "destroying TX queue %d\n", tx_queue->queue);
 445         falcon_remove_tx(tx_queue);
 446
 447         kfree(tx_queue->buffer);
 448         tx_queue->buffer = NULL;
 449         tx_queue->used = 0;
 450 }
 451
 452