netxen: cut-through rx changes

NX3031 supports cut-through operation where ingress packets are
directly dma'ed into host buffers to reduce latency.

This requires larger dma buffers (2kb) and different alignemnt.

The buffer posting logic is changed a bit. The free rx buffers
are maintained in linked list, since the received reference
handles can be out of order. However rx descriptors are still
posted sequentially, indexed by producer.

Signed-off-by: Dhananjay Phadke <dhananjay@netxen.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 130 insertions, 61 deletions

diff --git a/drivers/net/netxen/netxen_nic_init.c b/drivers/net/netxen/netxen_nic_init.c
index 7b5124057664..01ab31b34a85 100644
--- a/drivers/net/netxen/netxen_nic_init.c
+++ b/drivers/net/netxen/netxen_nic_init.c
@@ -262,17 +262,30 @@ int netxen_alloc_sw_resources(struct netxen_adapter *adapter)
                                 rds_ring->max_rx_desc_count =
                                         adapter->max_rx_desc_count;
                                 rds_ring->flags = RCV_DESC_NORMAL;
-                                rds_ring->dma_size = RX_DMA_MAP_LEN;
-                                rds_ring->skb_size = MAX_RX_BUFFER_LENGTH;
+                                if (adapter->ahw.cut_through) {
+                                        rds_ring->dma_size =
+                                                NX_CT_DEFAULT_RX_BUF_LEN;
+                                        rds_ring->skb_size =
+                                                NX_CT_DEFAULT_RX_BUF_LEN;
+                                } else {
+                                        rds_ring->dma_size = RX_DMA_MAP_LEN;
+                                        rds_ring->skb_size =
+                                                MAX_RX_BUFFER_LENGTH;
+                                }
                                 break;
 
                         case RCV_DESC_JUMBO:
                                 rds_ring->max_rx_desc_count =
                                         adapter->max_jumbo_rx_desc_count;
                                 rds_ring->flags = RCV_DESC_JUMBO;
-                                rds_ring->dma_size = RX_JUMBO_DMA_MAP_LEN;
+                                if (NX_IS_REVISION_P3(adapter->ahw.revision_id))
+                                        rds_ring->dma_size =
+                                                NX_P3_RX_JUMBO_BUF_MAX_LEN;
+                                else
+                                        rds_ring->dma_size =
+                                                NX_P2_RX_JUMBO_BUF_MAX_LEN;
                                 rds_ring->skb_size =
-                                        MAX_RX_JUMBO_BUFFER_LENGTH;
+                                        rds_ring->dma_size + NET_IP_ALIGN;
                                 break;
 
                         case RCV_RING_LRO:
@@ -294,6 +307,7 @@ int netxen_alloc_sw_resources(struct netxen_adapter *adapter)
                                 goto err_out;
                         }
                         memset(rds_ring->rx_buf_arr, 0, RCV_BUFFSIZE);
+                        INIT_LIST_HEAD(&rds_ring->free_list);
                         rds_ring->begin_alloc = 0;
                         /*
                          * Now go through all of them, set reference handles
@@ -302,6 +316,8 @@ int netxen_alloc_sw_resources(struct netxen_adapter *adapter)
                         num_rx_bufs = rds_ring->max_rx_desc_count;
                         rx_buf = rds_ring->rx_buf_arr;
                         for (i = 0; i < num_rx_bufs; i++) {
+                                list_add_tail(&rx_buf->list,
+                                                &rds_ring->free_list);
                                 rx_buf->ref_handle = i;
                                 rx_buf->state = NETXEN_BUFFER_FREE;
                                 rx_buf++;
@@ -1137,15 +1153,47 @@ int netxen_receive_peg_ready(struct netxen_adapter *adapter)
         return 0;
 }
 
+static struct sk_buff *netxen_process_rxbuf(struct netxen_adapter *adapter,
+                struct nx_host_rds_ring *rds_ring, u16 index, u16 cksum)
+{
+        struct netxen_rx_buffer *buffer;
+        struct sk_buff *skb;
+
+        buffer = &rds_ring->rx_buf_arr[index];
+
+        pci_unmap_single(adapter->pdev, buffer->dma, rds_ring->dma_size,
+                        PCI_DMA_FROMDEVICE);
+
+        skb = buffer->skb;
+        if (!skb)
+                goto no_skb;
+
+        if (likely(adapter->rx_csum && cksum == STATUS_CKSUM_OK)) {
+                adapter->stats.csummed++;
+                skb->ip_summed = CHECKSUM_UNNECESSARY;
+        } else
+                skb->ip_summed = CHECKSUM_NONE;
+
+        skb->dev = adapter->netdev;
+
+        buffer->skb = NULL;
+
+no_skb:
+        buffer->state = NETXEN_BUFFER_FREE;
+        buffer->lro_current_frags = 0;
+        buffer->lro_expected_frags = 0;
+        list_add_tail(&buffer->list, &rds_ring->free_list);
+        return skb;
+}
+
 /*
  * netxen_process_rcv() send the received packet to the protocol stack.
  * and if the number of receives exceeds RX_BUFFERS_REFILL, then we
  * invoke the routine to send more rx buffers to the Phantom...
  */
 static void netxen_process_rcv(struct netxen_adapter *adapter, int ctxid,
-                               struct status_desc *desc)
+                struct status_desc *desc, struct status_desc *frag_desc)
 {
-        struct pci_dev *pdev = adapter->pdev;
         struct net_device *netdev = adapter->netdev;
         u64 sts_data = le64_to_cpu(desc->status_desc_data);
         int index = netxen_get_sts_refhandle(sts_data);
@@ -1154,8 +1202,8 @@ static void netxen_process_rcv(struct netxen_adapter *adapter, int ctxid,
         struct sk_buff *skb;
         u32 length = netxen_get_sts_totallength(sts_data);
         u32 desc_ctx;
+        u16 pkt_offset = 0, cksum;
         struct nx_host_rds_ring *rds_ring;
-        int ret;
 
         desc_ctx = netxen_get_sts_type(sts_data);
         if (unlikely(desc_ctx >= NUM_RCV_DESC_RINGS)) {
@@ -1191,41 +1239,52 @@ static void netxen_process_rcv(struct netxen_adapter *adapter, int ctxid,
                 }
         }
 
-        pci_unmap_single(pdev, buffer->dma, rds_ring->dma_size,
-                         PCI_DMA_FROMDEVICE);
-
-        skb = (struct sk_buff *)buffer->skb;
+        cksum = netxen_get_sts_status(sts_data);
 
-        if (likely(adapter->rx_csum &&
-                        netxen_get_sts_status(sts_data) == STATUS_CKSUM_OK)) {
-                adapter->stats.csummed++;
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
-        } else
-                skb->ip_summed = CHECKSUM_NONE;
+        skb = netxen_process_rxbuf(adapter, rds_ring, index, cksum);
+        if (!skb)
+                return;
 
-        skb->dev = netdev;
         if (desc_ctx == RCV_DESC_LRO_CTXID) {
                 /* True length was only available on the last pkt */
                 skb_put(skb, buffer->lro_length);
         } else {
-                skb_put(skb, length);
+                if (length > rds_ring->skb_size)
+                        skb_put(skb, rds_ring->skb_size);
+                else
+                        skb_put(skb, length);
+
+                pkt_offset = netxen_get_sts_pkt_offset(sts_data);
+                if (pkt_offset)
+                        skb_pull(skb, pkt_offset);
         }
 
         skb->protocol = eth_type_trans(skb, netdev);
 
-        ret = netif_receive_skb(skb);
-        netdev->last_rx = jiffies;
-
         /*
-         * We just consumed one buffer so post a buffer.
+         * rx buffer chaining is disabled, walk and free
+         * any spurious rx buffer chain.
          */
-        buffer->skb = NULL;
-        buffer->state = NETXEN_BUFFER_FREE;
-        buffer->lro_current_frags = 0;
-        buffer->lro_expected_frags = 0;
+        if (frag_desc) {
+                u16 i, nr_frags = desc->nr_frags;
+
+                dev_kfree_skb_any(skb);
+                for (i = 0; i < nr_frags; i++) {
+                        index = frag_desc->frag_handles[i];
+                        skb = netxen_process_rxbuf(adapter,
+                                        rds_ring, index, cksum);
+                        if (skb)
+                                dev_kfree_skb_any(skb);
+                }
+                adapter->stats.rxdropped++;
+        } else {
 
-        adapter->stats.no_rcv++;
-        adapter->stats.rxbytes += length;
+                netif_receive_skb(skb);
+                netdev->last_rx = jiffies;
+
+                adapter->stats.no_rcv++;
+                adapter->stats.rxbytes += length;
+        }
 }
 
 /* Process Receive status ring */
@@ -1233,9 +1292,11 @@ u32 netxen_process_rcv_ring(struct netxen_adapter *adapter, int ctxid, int max)
 {
         struct netxen_recv_context *recv_ctx = &(adapter->recv_ctx[ctxid]);
         struct status_desc *desc_head = recv_ctx->rcv_status_desc_head;
-        struct status_desc *desc;       /* used to read status desc here */
+        struct status_desc *desc, *frag_desc;
         u32 consumer = recv_ctx->status_rx_consumer;
         int count = 0, ring;
+        u64 sts_data;
+        u16 opcode;
 
         while (count < max) {
                 desc = &desc_head[consumer];
@@ -1244,9 +1305,26 @@ u32 netxen_process_rcv_ring(struct netxen_adapter *adapter, int ctxid, int max)
                                 netxen_get_sts_owner(desc));
                         break;
                 }
-                netxen_process_rcv(adapter, ctxid, desc);
+
+                sts_data = le64_to_cpu(desc->status_desc_data);
+                opcode = netxen_get_sts_opcode(sts_data);
+                frag_desc = NULL;
+                if (opcode == NETXEN_NIC_RXPKT_DESC) {
+                        if (desc->nr_frags) {
+                                consumer = get_next_index(consumer,
+                                                adapter->max_rx_desc_count);
+                                frag_desc = &desc_head[consumer];
+                                netxen_set_sts_owner(frag_desc,
+                                                STATUS_OWNER_PHANTOM);
+                        }
+                }
+
+                netxen_process_rcv(adapter, ctxid, desc, frag_desc);
+
                 netxen_set_sts_owner(desc, STATUS_OWNER_PHANTOM);
-                consumer = (consumer + 1) & (adapter->max_rx_desc_count - 1);
+
+                consumer = get_next_index(consumer,
+                                adapter->max_rx_desc_count);
                 count++;
         }
         for (ring = 0; ring < adapter->max_rds_rings; ring++)
@@ -1348,36 +1426,31 @@ void netxen_post_rx_buffers(struct netxen_adapter *adapter, u32 ctx, u32 ringid)
         int index = 0;
         netxen_ctx_msg msg = 0;
         dma_addr_t dma;
+        struct list_head *head;
 
         rds_ring = &recv_ctx->rds_rings[ringid];
 
         producer = rds_ring->producer;
         index = rds_ring->begin_alloc;
-        buffer = &rds_ring->rx_buf_arr[index];
+        head = &rds_ring->free_list;
+
         /* We can start writing rx descriptors into the phantom memory. */
-        while (buffer->state == NETXEN_BUFFER_FREE) {
+        while (!list_empty(head)) {
+
                 skb = dev_alloc_skb(rds_ring->skb_size);
                 if (unlikely(!skb)) {
-                        /*
-                         * TODO
-                         * We need to schedule the posting of buffers to the pegs.
-                         */
                         rds_ring->begin_alloc = index;
-                        DPRINTK(ERR, "netxen_post_rx_buffers: "
-                                " allocated only %d buffers\n", count);
                         break;
                 }
 
+                buffer = list_entry(head->next, struct netxen_rx_buffer, list);
+                list_del(&buffer->list);
+
                 count++;        /* now there should be no failure */
                 pdesc = &rds_ring->desc_head[producer];
 
-#if defined(XGB_DEBUG)
-                *(unsigned long *)(skb->head) = 0xc0debabe;
-                if (skb_is_nonlinear(skb)) {
-                        printk("Allocated SKB @%p is nonlinear\n");
-                }
-#endif
-                skb_reserve(skb, 2);
+                if (!adapter->ahw.cut_through)
+                        skb_reserve(skb, 2);
                 /* This will be setup when we receive the
                  * buffer after it has been filled  FSL  TBD TBD
                  * skb->dev = netdev;
@@ -1395,7 +1468,6 @@ void netxen_post_rx_buffers(struct netxen_adapter *adapter, u32 ctx, u32 ringid)
                 producer =
                     get_next_index(producer, rds_ring->max_rx_desc_count);
                 index = get_next_index(index, rds_ring->max_rx_desc_count);
-                buffer = &rds_ring->rx_buf_arr[index];
         }
         /* if we did allocate buffers, then write the count to Phantom */
         if (count) {
@@ -1439,32 +1511,29 @@ static void netxen_post_rx_buffers_nodb(struct netxen_adapter *adapter,
         struct netxen_rx_buffer *buffer;
         int count = 0;
         int index = 0;
+        struct list_head *head;
 
         rds_ring = &recv_ctx->rds_rings[ringid];
 
         producer = rds_ring->producer;
         index = rds_ring->begin_alloc;
-        buffer = &rds_ring->rx_buf_arr[index];
+        head = &rds_ring->free_list;
         /* We can start writing rx descriptors into the phantom memory. */
-        while (buffer->state == NETXEN_BUFFER_FREE) {
+        while (!list_empty(head)) {
+
                 skb = dev_alloc_skb(rds_ring->skb_size);
                 if (unlikely(!skb)) {
-                        /*
-                         * We need to schedule the posting of buffers to the pegs.
-                         */
                         rds_ring->begin_alloc = index;
-                        DPRINTK(ERR, "netxen_post_rx_buffers_nodb: "
-                                " allocated only %d buffers\n", count);
                         break;
                 }
+
+                buffer = list_entry(head->next, struct netxen_rx_buffer, list);
+                list_del(&buffer->list);
+
                 count++;        /* now there should be no failure */
                 pdesc = &rds_ring->desc_head[producer];
-                skb_reserve(skb, 2);
-                /*
-                 * This will be setup when we receive the
-                 * buffer after it has been filled
-                 * skb->dev = netdev;
-                 */
+                if (!adapter->ahw.cut_through)
+                        skb_reserve(skb, 2);
                 buffer->skb = skb;
                 buffer->state = NETXEN_BUFFER_BUSY;
                 buffer->dma = pci_map_single(pdev, skb->data,