Altera TSE driver and example program for lwIP (1.3.2)

Bill,

Thank you for the confirmation and for the patch. With modified tse_mac_raw_send() both raw_api- and netconn-based tests work fine in my configuration.

I think that your simple solution should be OK for TCP, but may severely impact performance of udp applications if someone tries to achieve zero-copy by chaining headers-only pbuf with ROM- or REF-type payload-only pbuf. The both pbufs could be properly aligned and unnecessary and expensive unwinding may become a bottleneck. I don’t use this approach in my code currently, but advertised it earlier in this thread.

Below is my implementation of chain scanning as you suggested. I changed also to do unwinding in buf2[]. Is it ok, or you had good reasons to allocate separate pbuf for this purpose?

err_t tse_mac_raw_send(struct netif *netif, struct pbuf *pkt)
{
   int                tx_length;
   unsigned           len;
   struct pbuf        *p;
   alt_u32            *data;
   tse_mac_trans_info *mi;
   lwip_tse_info      *tse_ptr;
   struct ethernetif  *ethernetif;
   unsigned int       *ActualData;
   int unwind;
   /* Intermediate buffers used for temporary copy of frames that cannot be directrly DMA'ed*/
   struct pbuf unwind_pbuf;
   char buf2;
   ethernetif = netif->state;
   tse_ptr = ethernetif->tse_info;
   mi = &tse_ptr->mi;
   unwind = 0;
   for(p = pkt; p != NULL; p = p->next) {
       if (((unsigned long)p->payload & 0x03) != 0 || p->len < 4 || ((p->len & 3) != 0 && p->next)) {
           unwind = 1;
           break;
       }
   }
   if (unwind) {
       // Unwind pbuf chains
       if (pkt->tot_len > sizeof(buf2)) {
           // no space for unwinding; drop the packet
           return ERR_OK;
       }
       for(len = 0, p = pkt; p != NULL; p = p->next)
           {
             /*
              * Copy data to temporary buffer <buf2>. This is done because of allignment
              * issues. The SGDMA cannot copy the data directly from (data + ETH_PAD_SIZE)
              * because it needs a 32-bit alligned address space.
              */
           memcpy(buf2 + len, p->payload, p->len);
           len += p->len;
           }
       unwind_pbuf.len = unwind_pbuf.tot_len = len;
       unwind_pbuf.payload = buf2;
       unwind_pbuf.next = NULL;
       pkt = &unwind_pbuf;
   }
   for(p = pkt; p != NULL; p = p->next)
      {
      data = p->payload;
      len = p->len;
      // No need for re-alignment and length-checking here
      ActualData = (void *)alt_remap_uncached (data, len);
      //printf("<%d @ 0x%08X/0x%08X>", len, (unsigned int)p->payload, (unsigned int)ActualData);
      /* Write data to Tx FIFO using the DMA */
      alt_avalon_sgdma_construct_mem_to_stream_desc(
           (alt_sgdma_descriptor *) &tse_ptr->desc, // descriptor I want to work with
           (alt_sgdma_descriptor *) &tse_ptr->desc,// pointer to "next"
           (alt_u32*)ActualData,                    // starting read address
           (len),                                   //#  bytes
           0,                                       // don't read from constant address
           p == pkt,                                // generate sop
           p->next == NULL,                         // generate endofpacket signal
           0);                                      // atlantic channel (don't know/don't care: set to 0)
      tx_length = tse_mac_sTxWrite(mi,&tse_ptr->desc);
      ethernetif->bytes_sent += tx_length;
      }
   LINK_STATS_INC(link.xmit);
   return ERR_OK;
}