[PATCH] skge: Rx buffer optimization

Optimize the receive buffer management code to replenish the
buffers immediately (like tg3).

Signed-off-by: Stephen Hemmminger <shemminger@osdl.org>

2 files changed, 163 insertions, 103 deletions

diff --git a/drivers/net/skge.c b/drivers/net/skge.c
index 9f24714260be..9d4ae78b6ad9 100644
--- a/drivers/net/skge.c
+++ b/drivers/net/skge.c
@@ -49,6 +49,8 @@
 #define DEFAULT_RX_RING_SIZE    512
 #define MAX_TX_RING_SIZE        1024
 #define MAX_RX_RING_SIZE        4096
+#define RX_COPY_THRESHOLD       128
+#define RX_BUF_SIZE             1536
 #define PHY_RETRIES             1000
 #define ETH_JUMBO_MTU           9000
 #define TX_WATCHDOG             (5 * HZ)
@@ -746,6 +748,7 @@ static int skge_ring_alloc(struct skge_ring *ring, void *vaddr, u64 base)
 
         for (i = 0, e = ring->start, d = vaddr; i < ring->count; i++, e++, d++) {
                 e->desc = d;
+                e->skb = NULL;
                 if (i == ring->count - 1) {
                         e->next = ring->start;
                         d->next_offset = base;
@@ -759,24 +762,23 @@ static int skge_ring_alloc(struct skge_ring *ring, void *vaddr, u64 base)
         return 0;
 }
 
-/* Setup buffer for receiving */
-static inline int skge_rx_alloc(struct skge_port *skge,
-                                struct skge_element *e)
+static struct sk_buff *skge_rx_alloc(struct net_device *dev, unsigned int size)
 {
-        unsigned long bufsize = skge->netdev->mtu + ETH_HLEN; /* VLAN? */
-        struct skge_rx_desc *rd = e->desc;
-        struct sk_buff *skb;
-        u64 map;
+        struct sk_buff *skb = dev_alloc_skb(size);
 
-        skb = dev_alloc_skb(bufsize + NET_IP_ALIGN);
-        if (unlikely(!skb)) {
-                printk(KERN_DEBUG PFX "%s: out of memory for receive\n",
-                       skge->netdev->name);
-                return -ENOMEM;
+        if (likely(skb)) {
+                skb->dev = dev;
+                skb_reserve(skb, NET_IP_ALIGN);
         }
+        return skb;
+}
 
-        skb->dev = skge->netdev;
-        skb_reserve(skb, NET_IP_ALIGN);
+/* Allocate and setup a new buffer for receiving */
+static void skge_rx_setup(struct skge_port *skge, struct skge_element *e,
+                          struct sk_buff *skb, unsigned int bufsize)
+{
+        struct skge_rx_desc *rd = e->desc;
+        u64 map;
 
         map = pci_map_single(skge->hw->pdev, skb->data, bufsize,
                              PCI_DMA_FROMDEVICE);
@@ -794,55 +796,69 @@ static inline int skge_rx_alloc(struct skge_port *skge,
         rd->control = BMU_OWN | BMU_STF | BMU_IRQ_EOF | BMU_TCP_CHECK | bufsize;
         pci_unmap_addr_set(e, mapaddr, map);
         pci_unmap_len_set(e, maplen, bufsize);
-        return 0;
 }
 
-/* Free all unused buffers in receive ring, assumes receiver stopped */
+/* Resume receiving using existing skb,
+ * Note: DMA address is not changed by chip.
+ *       MTU not changed while receiver active.
+ */
+static void skge_rx_reuse(struct skge_element *e, unsigned int size)
+{
+        struct skge_rx_desc *rd = e->desc;
+
+        rd->csum2 = 0;
+        rd->csum2_start = ETH_HLEN;
+
+        wmb();
+
+        rd->control = BMU_OWN | BMU_STF | BMU_IRQ_EOF | BMU_TCP_CHECK | size;
+}
+
+
+/* Free all  buffers in receive ring, assumes receiver stopped */
 static void skge_rx_clean(struct skge_port *skge)
 {
         struct skge_hw *hw = skge->hw;
         struct skge_ring *ring = &skge->rx_ring;
         struct skge_element *e;
 
-        for (e = ring->to_clean; e != ring->to_use; e = e->next) {
+        e = ring->start;
+        do {
                 struct skge_rx_desc *rd = e->desc;
                 rd->control = 0;
-
-                pci_unmap_single(hw->pdev,
-                                 pci_unmap_addr(e, mapaddr),
-                                 pci_unmap_len(e, maplen),
-                                 PCI_DMA_FROMDEVICE);
-                dev_kfree_skb(e->skb);
-                e->skb = NULL;
-        }
-        ring->to_clean = e;
+                if (e->skb) {
+                        pci_unmap_single(hw->pdev,
+                                         pci_unmap_addr(e, mapaddr),
+                                         pci_unmap_len(e, maplen),
+                                         PCI_DMA_FROMDEVICE);
+                        dev_kfree_skb(e->skb);
+                        e->skb = NULL;
+                }
+        } while ((e = e->next) != ring->start);
 }
 
+
 /* Allocate buffers for receive ring
- * For receive: to_use   is refill location
- *              to_clean is next received frame.
- *
- * if (to_use == to_clean)
- *       then ring all frames in ring need buffers
- * if (to_use->next == to_clean)
- *       then ring all frames in ring have buffers
+ * For receive:  to_clean is next received frame.
  */
 static int skge_rx_fill(struct skge_port *skge)
 {
         struct skge_ring *ring = &skge->rx_ring;
         struct skge_element *e;
-        int ret = 0;
+        unsigned int bufsize = skge->rx_buf_size;
 
-        for (e = ring->to_use; e->next != ring->to_clean; e = e->next) {
-                if (skge_rx_alloc(skge, e)) {
-                        ret = 1;
-                        break;
-                }
+        e = ring->start;
+        do {
+                struct sk_buff *skb = skge_rx_alloc(skge->netdev, bufsize);
 
-        }
-        ring->to_use = e;
+                if (!skb)
+                        return -ENOMEM;
+
+                skge_rx_setup(skge, e, skb, bufsize);
+        } while ( (e = e->next) != ring->start);
 
-        return ret;
+        ring->to_clean = ring->start;
+        return 0;
 }
 
 static void skge_link_up(struct skge_port *skge)
@@ -2048,6 +2064,12 @@ static int skge_up(struct net_device *dev)
         if (netif_msg_ifup(skge))
                 printk(KERN_INFO PFX "%s: enabling interface\n", dev->name);
 
+        if (dev->mtu > RX_BUF_SIZE)
+                skge->rx_buf_size = dev->mtu + ETH_HLEN + NET_IP_ALIGN;
+        else
+                skge->rx_buf_size = RX_BUF_SIZE;
+
+
         rx_size = skge->rx_ring.count * sizeof(struct skge_rx_desc);
         tx_size = skge->tx_ring.count * sizeof(struct skge_tx_desc);
         skge->mem_size = tx_size + rx_size;
@@ -2060,7 +2082,8 @@ static int skge_up(struct net_device *dev)
         if ((err = skge_ring_alloc(&skge->rx_ring, skge->mem, skge->dma)))
                 goto free_pci_mem;
 
-        if (skge_rx_fill(skge))
+        err = skge_rx_fill(skge);
+        if (err)
                 goto free_rx_ring;
 
         if ((err = skge_ring_alloc(&skge->tx_ring, skge->mem + rx_size,
@@ -2284,6 +2307,7 @@ static int skge_xmit_frame(struct sk_buff *skb, struct net_device *dev)
 
 static inline void skge_tx_free(struct skge_hw *hw, struct skge_element *e)
 {
+        /* This ring element can be skb or fragment */
         if (e->skb) {
                 pci_unmap_single(hw->pdev,
                                pci_unmap_addr(e, mapaddr),
@@ -2328,16 +2352,17 @@ static void skge_tx_timeout(struct net_device *dev)
 static int skge_change_mtu(struct net_device *dev, int new_mtu)
 {
         int err = 0;
+        int running = netif_running(dev);
 
         if (new_mtu < ETH_ZLEN || new_mtu > ETH_JUMBO_MTU)
                 return -EINVAL;
 
-        dev->mtu = new_mtu;
 
-        if (netif_running(dev)) {
+        if (running)
                 skge_down(dev);
+        dev->mtu = new_mtu;
+        if (running)
                 skge_up(dev);
-        }
 
         return err;
 }
@@ -2436,28 +2461,76 @@ static void skge_rx_error(struct skge_port *skge, int slot,
                 printk(KERN_DEBUG PFX "%s: rx err, slot %d control 0x%x status 0x%x\n",
                        skge->netdev->name, slot, control, status);
 
-        if ((control & (BMU_EOF|BMU_STF)) != (BMU_STF|BMU_EOF)
-            || (control & BMU_BBC) > skge->netdev->mtu + VLAN_ETH_HLEN)
+        if ((control & (BMU_EOF|BMU_STF)) != (BMU_STF|BMU_EOF))
                 skge->net_stats.rx_length_errors++;
-        else {
-                if (skge->hw->chip_id == CHIP_ID_GENESIS) {
-                        if (status & (XMR_FS_RUNT|XMR_FS_LNG_ERR))
-                                skge->net_stats.rx_length_errors++;
-                        if (status & XMR_FS_FRA_ERR)
-                                skge->net_stats.rx_frame_errors++;
-                        if (status & XMR_FS_FCS_ERR)
-                                skge->net_stats.rx_crc_errors++;
-                } else {
-                        if (status & (GMR_FS_LONG_ERR|GMR_FS_UN_SIZE))
-                                skge->net_stats.rx_length_errors++;
-                        if (status & GMR_FS_FRAGMENT)
-                                skge->net_stats.rx_frame_errors++;
-                        if (status & GMR_FS_CRC_ERR)
-                                skge->net_stats.rx_crc_errors++;
+        else if (skge->hw->chip_id == CHIP_ID_GENESIS) {
+                if (status & (XMR_FS_RUNT|XMR_FS_LNG_ERR))
+                        skge->net_stats.rx_length_errors++;
+                if (status & XMR_FS_FRA_ERR)
+                        skge->net_stats.rx_frame_errors++;
+                if (status & XMR_FS_FCS_ERR)
+                        skge->net_stats.rx_crc_errors++;
+        } else {
+                if (status & (GMR_FS_LONG_ERR|GMR_FS_UN_SIZE))
+                        skge->net_stats.rx_length_errors++;
+                if (status & GMR_FS_FRAGMENT)
+                        skge->net_stats.rx_frame_errors++;
+                if (status & GMR_FS_CRC_ERR)
+                        skge->net_stats.rx_crc_errors++;
+        }
+}
+
+/* Get receive buffer from descriptor.
+ * Handles copy of small buffers and reallocation failures
+ */
+static inline struct sk_buff *skge_rx_get(struct skge_port *skge,
+                                          struct skge_element *e,
+                                          unsigned int len)
+{
+        struct sk_buff *nskb, *skb;
+
+        if (len < RX_COPY_THRESHOLD) {
+                nskb = skge_rx_alloc(skge->netdev, len + NET_IP_ALIGN);
+                if (unlikely(!nskb))
+                        return NULL;
+
+                pci_dma_sync_single_for_cpu(skge->hw->pdev,
+                                            pci_unmap_addr(e, mapaddr),
+                                            len, PCI_DMA_FROMDEVICE);
+                memcpy(nskb->data, e->skb->data, len);
+                pci_dma_sync_single_for_device(skge->hw->pdev,
+                                               pci_unmap_addr(e, mapaddr),
+                                               len, PCI_DMA_FROMDEVICE);
+
+                if (skge->rx_csum) {
+                        struct skge_rx_desc *rd = e->desc;
+                        nskb->csum = le16_to_cpu(rd->csum2);
+                        nskb->ip_summed = CHECKSUM_HW;
+                }
+                skge_rx_reuse(e, skge->rx_buf_size);
+                return nskb;
+        } else {
+                nskb = skge_rx_alloc(skge->netdev, skge->rx_buf_size);
+                if (unlikely(!nskb))
+                        return NULL;
+
+                pci_unmap_single(skge->hw->pdev,
+                                 pci_unmap_addr(e, mapaddr),
+                                 pci_unmap_len(e, maplen),
+                                 PCI_DMA_FROMDEVICE);
+                skb = e->skb;
+                if (skge->rx_csum) {
+                        struct skge_rx_desc *rd = e->desc;
+                        skb->csum = le16_to_cpu(rd->csum2);
+                        skb->ip_summed = CHECKSUM_HW;
                 }
+
+                skge_rx_setup(skge, e, nskb, skge->rx_buf_size);
+                return skb;
         }
 }
 
+
 static int skge_poll(struct net_device *dev, int *budget)
 {
         struct skge_port *skge = netdev_priv(dev);
@@ -2466,14 +2539,12 @@ static int skge_poll(struct net_device *dev, int *budget)
         struct skge_element *e;
         unsigned int to_do = min(dev->quota, *budget);
         unsigned int work_done = 0;
-        int done;
 
         pr_debug("skge_poll\n");
 
-        for (e = ring->to_clean; e != ring->to_use && work_done < to_do;
-             e = e->next) {
+        for (e = ring->to_clean; work_done < to_do; e = e->next) {
                 struct skge_rx_desc *rd = e->desc;
-                struct sk_buff *skb = e->skb;
+                struct sk_buff *skb;
                 u32 control, len, status;
 
                 rmb();
@@ -2482,19 +2553,12 @@ static int skge_poll(struct net_device *dev, int *budget)
                         break;
 
                 len = control & BMU_BBC;
-                e->skb = NULL;
-
-                pci_unmap_single(hw->pdev,
-                                 pci_unmap_addr(e, mapaddr),
-                                 pci_unmap_len(e, maplen),
-                                 PCI_DMA_FROMDEVICE);
-
                 status = rd->status;
-                if ((control & (BMU_EOF|BMU_STF)) != (BMU_STF|BMU_EOF)
-                     || len > dev->mtu + VLAN_ETH_HLEN
-                     || bad_phy_status(hw, status)) {
+
+                if (unlikely((control & (BMU_EOF|BMU_STF)) != (BMU_STF|BMU_EOF)
+                             || bad_phy_status(hw, status))) {
                         skge_rx_error(skge, e - ring->start, control, status);
-                        dev_kfree_skb(skb);
+                        skge_rx_reuse(e, skge->rx_buf_size);
                         continue;
                 }
 
@@ -2502,42 +2566,37 @@ static int skge_poll(struct net_device *dev, int *budget)
                     printk(KERN_DEBUG PFX "%s: rx slot %td status 0x%x len %d\n",
                            dev->name, e - ring->start, rd->status, len);
 
-                skb_put(skb, len);
-                skb->protocol = eth_type_trans(skb, dev);
+                skb = skge_rx_get(skge, e, len);
+                if (likely(skb)) {
+                        skb_put(skb, len);
+                        skb->protocol = eth_type_trans(skb, dev);
 
-                if (skge->rx_csum) {
-                        skb->csum = le16_to_cpu(rd->csum2);
-                        skb->ip_summed = CHECKSUM_HW;
-                }
-
-                dev->last_rx = jiffies;
-                netif_receive_skb(skb);
+                        dev->last_rx = jiffies;
+                        netif_receive_skb(skb);
 
-                ++work_done;
+                        ++work_done;
+                } else
+                        skge_rx_reuse(e, skge->rx_buf_size);
         }
         ring->to_clean = e;
 
-        *budget -= work_done;
-        dev->quota -= work_done;
-        done = work_done < to_do;
-
-        if (skge_rx_fill(skge))
-                done = 0;
-
         /* restart receiver */
         wmb();
         skge_write8(hw, Q_ADDR(rxqaddr[skge->port], Q_CSR),
                     CSR_START | CSR_IRQ_CL_F);
 
-        if (done) {
-                local_irq_disable();
-                __netif_rx_complete(dev);
-                hw->intr_mask |= portirqmask[skge->port];
-                skge_write32(hw, B0_IMSK, hw->intr_mask);
-                local_irq_enable();
-        }
+        *budget -= work_done;
+        dev->quota -= work_done;
+
+        if (work_done >=  to_do)
+                return 1; /* not done */
 
-        return !done;
+        local_irq_disable();
+        __netif_rx_complete(dev);
+        hw->intr_mask |= portirqmask[skge->port];
+        skge_write32(hw, B0_IMSK, hw->intr_mask);
+        local_irq_enable();
+        return 0;
 }
 
 static inline void skge_tx_intr(struct net_device *dev)
diff --git a/drivers/net/skge.h b/drivers/net/skge.h
index 37323cd29e7e..14d0cc01fb9a 100644
--- a/drivers/net/skge.h
+++ b/drivers/net/skge.h
@@ -2503,6 +2503,7 @@ struct skge_port {
         void                 *mem;      /* PCI memory for rings */
         dma_addr_t           dma;
         unsigned long        mem_size;
+        unsigned int         rx_buf_size;
 
         struct timer_list    led_blink;
 };