ftgmac100: Add support for fragmented tx

Add NETIF_F_SG and create multiple TX ring entries for skb fragments.

On reclaim, the skb is only freed on the segment marked as "last".

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 94 insertions, 25 deletions

diff --git a/drivers/net/ethernet/faraday/ftgmac100.c b/drivers/net/ethernet/faraday/ftgmac100.c
index d303c597e9b8..abe2442673a0 100644
--- a/drivers/net/ethernet/faraday/ftgmac100.c
+++ b/drivers/net/ethernet/faraday/ftgmac100.c
@@ -47,7 +47,7 @@
 #define RX_BUF_SIZE             MAX_PKT_SIZE    /* must be smaller than 0x3fff */
 
 /* Min number of tx ring entries before stopping queue */
-#define TX_THRESHOLD            (1)
+#define TX_THRESHOLD            (MAX_SKB_FRAGS + 1)
 
 struct ftgmac100_descs {
         struct ftgmac100_rxdes rxdes[RX_QUEUE_ENTRIES];
@@ -489,20 +489,30 @@ static void ftgmac100_txdes_set_first_segment(struct ftgmac100_txdes *txdes)
         txdes->txdes0 |= cpu_to_le32(FTGMAC100_TXDES0_FTS);
 }
 
+static inline bool ftgmac100_txdes_get_first_segment(struct ftgmac100_txdes *txdes)
+{
+        return (txdes->txdes0 & cpu_to_le32(FTGMAC100_TXDES0_FTS)) != 0;
+}
+
 static void ftgmac100_txdes_set_last_segment(struct ftgmac100_txdes *txdes)
 {
         txdes->txdes0 |= cpu_to_le32(FTGMAC100_TXDES0_LTS);
 }
 
+static inline bool ftgmac100_txdes_get_last_segment(struct ftgmac100_txdes *txdes)
+{
+        return (txdes->txdes0 & cpu_to_le32(FTGMAC100_TXDES0_LTS)) != 0;
+}
+
 static void ftgmac100_txdes_set_buffer_size(struct ftgmac100_txdes *txdes,
                                             unsigned int len)
 {
         txdes->txdes0 |= cpu_to_le32(FTGMAC100_TXDES0_TXBUF_SIZE(len));
 }
 
-static void ftgmac100_txdes_set_txint(struct ftgmac100_txdes *txdes)
+static inline unsigned int ftgmac100_txdes_get_buffer_size(struct ftgmac100_txdes *txdes)
 {
-        txdes->txdes1 |= cpu_to_le32(FTGMAC100_TXDES1_TXIC);
+        return FTGMAC100_TXDES0_TXBUF_SIZE(cpu_to_le32(txdes->txdes0));
 }
 
 static void ftgmac100_txdes_set_tcpcs(struct ftgmac100_txdes *txdes)
@@ -528,7 +538,7 @@ static void ftgmac100_txdes_set_dma_addr(struct ftgmac100_txdes *txdes,
 
 static dma_addr_t ftgmac100_txdes_get_dma_addr(struct ftgmac100_txdes *txdes)
 {
-        return le32_to_cpu(txdes->txdes3);
+        return (dma_addr_t)le32_to_cpu(txdes->txdes3);
 }
 
 static int ftgmac100_next_tx_pointer(int pointer)
@@ -558,13 +568,19 @@ static void ftgmac100_free_tx_packet(struct ftgmac100 *priv,
                                      struct sk_buff *skb,
                                      struct ftgmac100_txdes *txdes)
 {
-        dma_addr_t map;
+        dma_addr_t map = ftgmac100_txdes_get_dma_addr(txdes);
 
-        map = ftgmac100_txdes_get_dma_addr(txdes);
-
-        dma_unmap_single(priv->dev, map, skb_headlen(skb), DMA_TO_DEVICE);
+        if (ftgmac100_txdes_get_first_segment(txdes)) {
+                dma_unmap_single(priv->dev, map, skb_headlen(skb),
+                                 DMA_TO_DEVICE);
+        } else {
+                dma_unmap_page(priv->dev, map,
+                               ftgmac100_txdes_get_buffer_size(txdes),
+                               DMA_TO_DEVICE);
+        }
 
-        dev_kfree_skb(skb);
+        if (ftgmac100_txdes_get_last_segment(txdes))
+                dev_kfree_skb(skb);
         priv->tx_skbs[pointer] = NULL;
 
         /* Clear txdes0 except end of ring bit, clear txdes1 as we
@@ -626,8 +642,8 @@ static int ftgmac100_hard_start_xmit(struct sk_buff *skb,
                                      struct net_device *netdev)
 {
         struct ftgmac100 *priv = netdev_priv(netdev);
-        struct ftgmac100_txdes *txdes;
-        unsigned int pointer;
+        struct ftgmac100_txdes *txdes, *first;
+        unsigned int pointer, nfrags, len, i, j;
         dma_addr_t map;
 
         /* The HW doesn't pad small frames */
@@ -643,26 +659,33 @@ static int ftgmac100_hard_start_xmit(struct sk_buff *skb,
                 goto drop;
         }
 
-        map = dma_map_single(priv->dev, skb->data, skb_headlen(skb), DMA_TO_DEVICE);
-        if (unlikely(dma_mapping_error(priv->dev, map))) {
-                /* drop packet */
+        /* Do we have a limit on #fragments ? I yet have to get a reply
+         * from Aspeed. If there's one I haven't hit it.
+         */
+        nfrags = skb_shinfo(skb)->nr_frags;
+
+        /* Get header len */
+        len = skb_headlen(skb);
+
+        /* Map the packet head */
+        map = dma_map_single(priv->dev, skb->data, len, DMA_TO_DEVICE);
+        if (dma_mapping_error(priv->dev, map)) {
                 if (net_ratelimit())
-                        netdev_err(netdev, "map socket buffer failed\n");
+                        netdev_err(netdev, "map tx packet head failed\n");
                 goto drop;
         }
 
         /* Grab the next free tx descriptor */
         pointer = priv->tx_pointer;
-        txdes = &priv->descs->txdes[pointer];
+        txdes = first = &priv->descs->txdes[pointer];
 
-        /* setup TX descriptor */
+        /* Setup it up with the packet head. We don't set the OWN bit yet. */
         priv->tx_skbs[pointer] = skb;
         ftgmac100_txdes_set_dma_addr(txdes, map);
-        ftgmac100_txdes_set_buffer_size(txdes, skb->len);
-
+        ftgmac100_txdes_set_buffer_size(txdes, len);
         ftgmac100_txdes_set_first_segment(txdes);
-        ftgmac100_txdes_set_last_segment(txdes);
-        ftgmac100_txdes_set_txint(txdes);
+
+        /* Setup HW checksumming */
         if (skb->ip_summed == CHECKSUM_PARTIAL) {
                 __be16 protocol = skb->protocol;
 
@@ -677,14 +700,41 @@ static int ftgmac100_hard_start_xmit(struct sk_buff *skb,
                 }
         }
 
+        /* Next descriptor */
+        pointer = ftgmac100_next_tx_pointer(pointer);
+
+        /* Add the fragments */
+        for (i = 0; i < nfrags; i++) {
+                skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+
+                len = frag->size;
+
+                /* Map it */
+                map = skb_frag_dma_map(priv->dev, frag, 0, len,
+                                       DMA_TO_DEVICE);
+                if (dma_mapping_error(priv->dev, map))
+                        goto dma_err;
+
+                /* Setup descriptor */
+                priv->tx_skbs[pointer] = skb;
+                txdes = &priv->descs->txdes[pointer];
+                ftgmac100_txdes_set_dma_addr(txdes, map);
+                ftgmac100_txdes_set_buffer_size(txdes, len);
+                ftgmac100_txdes_set_dma_own(txdes);
+                pointer = ftgmac100_next_tx_pointer(pointer);
+        }
+
+        /* Tag last fragment */
+        ftgmac100_txdes_set_last_segment(txdes);
+
         /* Order the previous packet and descriptor udpates
          * before setting the OWN bit.
          */
         dma_wmb();
-        ftgmac100_txdes_set_dma_own(txdes);
+        ftgmac100_txdes_set_dma_own(first);
 
         /* Update next TX pointer */
-        priv->tx_pointer = ftgmac100_next_tx_pointer(pointer);
+        priv->tx_pointer = pointer;
 
         /* If there isn't enough room for all the fragments of a new packet
          * in the TX ring, stop the queue. The sequence below is race free
@@ -702,6 +752,25 @@ static int ftgmac100_hard_start_xmit(struct sk_buff *skb,
 
         return NETDEV_TX_OK;
 
+ dma_err:
+        if (net_ratelimit())
+                netdev_err(netdev, "map tx fragment failed\n");
+
+        /* Free head */
+        pointer = priv->tx_pointer;
+        ftgmac100_free_tx_packet(priv, pointer, skb, first);
+
+        /* Then all fragments */
+        for (j = 0; j < i; j++) {
+                pointer = ftgmac100_next_tx_pointer(pointer);
+                txdes = &priv->descs->txdes[pointer];
+                ftgmac100_free_tx_packet(priv, pointer, skb, txdes);
+        }
+
+        /* This cannot be reached if we successfully mapped the
+         * last fragment, so we know ftgmac100_free_tx_packet()
+         * hasn't freed the skb yet.
+         */
  drop:
         /* Drop the packet */
         dev_kfree_skb_any(skb);
@@ -1441,12 +1510,12 @@ static int ftgmac100_probe(struct platform_device *pdev)
          * when NCSI is enabled on the interface. It doesn't work
          * in that case.
          */
-        netdev->features = NETIF_F_RXCSUM | NETIF_F_IP_CSUM | NETIF_F_GRO;
+        netdev->features = NETIF_F_RXCSUM | NETIF_F_IP_CSUM |
+                NETIF_F_GRO | NETIF_F_SG;
         if (priv->use_ncsi &&
             of_get_property(pdev->dev.of_node, "no-hw-checksum", NULL))
                 netdev->features &= ~NETIF_F_IP_CSUM;
 
-
         /* register network device */
         err = register_netdev(netdev);
         if (err) {