[PATCH] sky2: fragmented receive for large MTU

Use hardware support for chained receive to break up large frames
into multiple pages. This avoids having to do a mult-page allocation
that can fail on a busy system due to fragmented memory.

For normal size MTU, this code behaves the same.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

2 files changed, 219 insertions, 81 deletions

diff --git a/drivers/net/sky2.c b/drivers/net/sky2.c
index c83d7262a5a8..7b19db598ff4 100644
--- a/drivers/net/sky2.c
+++ b/drivers/net/sky2.c
@@ -56,13 +56,12 @@
 /*
  * The Yukon II chipset takes 64 bit command blocks (called list elements)
  * that are organized into three (receive, transmit, status) different rings
- * similar to Tigon3. A transmit can require several elements;
- * a receive requires one (or two if using 64 bit dma).
+ * similar to Tigon3.
  */
 
-#define RX_LE_SIZE              512
+#define RX_LE_SIZE              1024
 #define RX_LE_BYTES             (RX_LE_SIZE*sizeof(struct sky2_rx_le))
-#define RX_MAX_PENDING          (RX_LE_SIZE/2 - 2)
+#define RX_MAX_PENDING          (RX_LE_SIZE/6 - 2)
 #define RX_DEF_PENDING          RX_MAX_PENDING
 #define RX_SKB_ALIGN            8
 #define RX_BUF_WRITE            16
@@ -74,7 +73,6 @@
 
 #define STATUS_RING_SIZE        2048    /* 2 ports * (TX + 2*RX) */
 #define STATUS_LE_BYTES         (STATUS_RING_SIZE*sizeof(struct sky2_status_le))
-#define ETH_JUMBO_MTU           9000
 #define TX_WATCHDOG             (5 * HZ)
 #define NAPI_WEIGHT             64
 #define PHY_RETRIES             1000
@@ -90,7 +88,7 @@ static int debug = -1;		/* defaults above */
 module_param(debug, int, 0);
 MODULE_PARM_DESC(debug, "Debug level (0=none,...,16=all)");
 
-static int copybreak __read_mostly = 256;
+static int copybreak __read_mostly = 128;
 module_param(copybreak, int, 0);
 MODULE_PARM_DESC(copybreak, "Receive copy threshold");
 
@@ -803,12 +801,12 @@ static inline u32 high32(dma_addr_t a)
         return sizeof(a) > sizeof(u32) ? (a >> 16) >> 16 : 0;
 }
 
-/* Build description to hardware about buffer */
-static void sky2_rx_add(struct sky2_port *sky2, dma_addr_t map)
+/* Build description to hardware for one receive segment */
+static void sky2_rx_add(struct sky2_port *sky2,  u8 op,
+                        dma_addr_t map, unsigned len)
 {
         struct sky2_rx_le *le;
         u32 hi = high32(map);
-        u16 len = sky2->rx_bufsize;
 
         if (sky2->rx_addr64 != hi) {
                 le = sky2_next_rx(sky2);
@@ -820,9 +818,52 @@ static void sky2_rx_add(struct sky2_port *sky2, dma_addr_t map)
         le = sky2_next_rx(sky2);
         le->addr = cpu_to_le32((u32) map);
         le->length = cpu_to_le16(len);
-        le->opcode = OP_PACKET | HW_OWNER;
+        le->opcode = op | HW_OWNER;
 }
 
+/* Build description to hardware for one possibly fragmented skb */
+static void sky2_rx_submit(struct sky2_port *sky2,
+                           const struct rx_ring_info *re)
+{
+        int i;
+
+        sky2_rx_add(sky2, OP_PACKET, re->data_addr, sky2->rx_data_size);
+
+        for (i = 0; i < skb_shinfo(re->skb)->nr_frags; i++)
+                sky2_rx_add(sky2, OP_BUFFER, re->frag_addr[i], PAGE_SIZE);
+}
+
+
+static void sky2_rx_map_skb(struct pci_dev *pdev, struct rx_ring_info *re,
+                            unsigned size)
+{
+        struct sk_buff *skb = re->skb;
+        int i;
+
+        re->data_addr = pci_map_single(pdev, skb->data, size, PCI_DMA_FROMDEVICE);
+        pci_unmap_len_set(re, data_size, size);
+
+        for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
+                re->frag_addr[i] = pci_map_page(pdev,
+                                                skb_shinfo(skb)->frags[i].page,
+                                                skb_shinfo(skb)->frags[i].page_offset,
+                                                skb_shinfo(skb)->frags[i].size,
+                                                PCI_DMA_FROMDEVICE);
+}
+
+static void sky2_rx_unmap_skb(struct pci_dev *pdev, struct rx_ring_info *re)
+{
+        struct sk_buff *skb = re->skb;
+        int i;
+
+        pci_unmap_single(pdev, re->data_addr, pci_unmap_len(re, data_size),
+                         PCI_DMA_FROMDEVICE);
+
+        for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
+                pci_unmap_page(pdev, re->frag_addr[i],
+                               skb_shinfo(skb)->frags[i].size,
+                               PCI_DMA_FROMDEVICE);
+}
 
 /* Tell chip where to start receive checksum.
  * Actually has two checksums, but set both same to avoid possible byte
@@ -886,9 +927,7 @@ static void sky2_rx_clean(struct sky2_port *sky2)
                 struct rx_ring_info *re = sky2->rx_ring + i;
 
                 if (re->skb) {
-                        pci_unmap_single(sky2->hw->pdev,
-                                         re->mapaddr, sky2->rx_bufsize,
-                                         PCI_DMA_FROMDEVICE);
+                        sky2_rx_unmap_skb(sky2->hw->pdev, re);
                         kfree_skb(re->skb);
                         re->skb = NULL;
                 }
@@ -969,38 +1008,57 @@ static void sky2_vlan_rx_kill_vid(struct net_device *dev, unsigned short vid)
 #endif
 
 /*
+ * Allocate an skb for receiving. If the MTU is large enough
+ * make the skb non-linear with a fragment list of pages.
+ *
  * It appears the hardware has a bug in the FIFO logic that
  * cause it to hang if the FIFO gets overrun and the receive buffer
  * is not 64 byte aligned. The buffer returned from netdev_alloc_skb is
  * aligned except if slab debugging is enabled.
  */
-static inline struct sk_buff *sky2_alloc_skb(struct net_device *dev,
-                                             unsigned int length,
-                                             gfp_t gfp_mask)
+static struct sk_buff *sky2_rx_alloc(struct sky2_port *sky2)
 {
         struct sk_buff *skb;
+        unsigned long p;
+        int i;
 
-        skb = __netdev_alloc_skb(dev, length + RX_SKB_ALIGN, gfp_mask);
-        if (likely(skb)) {
-                unsigned long p = (unsigned long) skb->data;
-                skb_reserve(skb, ALIGN(p, RX_SKB_ALIGN) - p);
+        skb = netdev_alloc_skb(sky2->netdev, sky2->rx_data_size + RX_SKB_ALIGN);
+        if (!skb)
+                goto nomem;
+
+        p = (unsigned long) skb->data;
+        skb_reserve(skb, ALIGN(p, RX_SKB_ALIGN) - p);
+
+        for (i = 0; i < sky2->rx_nfrags; i++) {
+                struct page *page = alloc_page(GFP_ATOMIC);
+
+                if (!page)
+                        goto free_partial;
+                skb_fill_page_desc(skb, i, page, 0, PAGE_SIZE);
         }
 
         return skb;
+free_partial:
+        kfree_skb(skb);
+nomem:
+        return NULL;
 }
 
 /*
  * Allocate and setup receiver buffer pool.
- * In case of 64 bit dma, there are 2X as many list elements
- * available as ring entries
- * and need to reserve one list element so we don't wrap around.
+ * Normal case this ends up creating one list element for skb
+ * in the receive ring. Worst case if using large MTU and each
+ * allocation falls on a different 64 bit region, that results
+ * in 6 list elements per ring entry.
+ * One element is used for checksum enable/disable, and one
+ * extra to avoid wrap.
  */
 static int sky2_rx_start(struct sky2_port *sky2)
 {
         struct sky2_hw *hw = sky2->hw;
+        struct rx_ring_info *re;
         unsigned rxq = rxqaddr[sky2->port];
-        int i;
-        unsigned thresh;
+        unsigned i, size, space, thresh;
 
         sky2->rx_put = sky2->rx_next = 0;
         sky2_qset(hw, rxq);
@@ -1013,27 +1071,56 @@ static int sky2_rx_start(struct sky2_port *sky2)
         sky2_prefetch_init(hw, rxq, sky2->rx_le_map, RX_LE_SIZE - 1);
 
         rx_set_checksum(sky2);
+
+        /* Space needed for frame data + headers rounded up */
+        size = ALIGN(sky2->netdev->mtu + ETH_HLEN + VLAN_HLEN, 8)
+                + 8;
+
+        /* Stopping point for hardware truncation */
+        thresh = (size - 8) / sizeof(u32);
+
+        /* Account for overhead of skb - to avoid order > 0 allocation */
+        space = SKB_DATA_ALIGN(size) + NET_SKB_PAD
+                + sizeof(struct skb_shared_info);
+
+        sky2->rx_nfrags = space >> PAGE_SHIFT;
+        BUG_ON(sky2->rx_nfrags > ARRAY_SIZE(re->frag_addr));
+
+        if (sky2->rx_nfrags != 0) {
+                /* Compute residue after pages */
+                space = sky2->rx_nfrags << PAGE_SHIFT;
+
+                if (space < size)
+                        size -= space;
+                else
+                        size = 0;
+
+                /* Optimize to handle small packets and headers */
+                if (size < copybreak)
+                        size = copybreak;
+                if (size < ETH_HLEN)
+                        size = ETH_HLEN;
+        }
+        sky2->rx_data_size = size;
+
+        /* Fill Rx ring */
         for (i = 0; i < sky2->rx_pending; i++) {
-                struct rx_ring_info *re = sky2->rx_ring + i;
+                re = sky2->rx_ring + i;
 
-                re->skb = sky2_alloc_skb(sky2->netdev, sky2->rx_bufsize,
-                                         GFP_KERNEL);
+                re->skb = sky2_rx_alloc(sky2);
                 if (!re->skb)
                         goto nomem;
 
-                re->mapaddr = pci_map_single(hw->pdev, re->skb->data,
-                                             sky2->rx_bufsize, PCI_DMA_FROMDEVICE);
-                sky2_rx_add(sky2, re->mapaddr);
+                sky2_rx_map_skb(hw->pdev, re, sky2->rx_data_size);
+                sky2_rx_submit(sky2, re);
         }
 
-
         /*
          * The receiver hangs if it receives frames larger than the
          * packet buffer. As a workaround, truncate oversize frames, but
          * the register is limited to 9 bits, so if you do frames > 2052
          * you better get the MTU right!
          */
-        thresh = (sky2->rx_bufsize - 8) / sizeof(u32);
         if (thresh > 0x1ff)
                 sky2_write32(hw, SK_REG(sky2->port, RX_GMF_CTRL_T), RX_TRUNC_OFF);
         else {
@@ -1041,7 +1128,6 @@ static int sky2_rx_start(struct sky2_port *sky2)
                 sky2_write32(hw, SK_REG(sky2->port, RX_GMF_CTRL_T), RX_TRUNC_ON);
         }
 
-
         /* Tell chip about available buffers */
         sky2_write16(hw, Y2_QADDR(rxq, PREF_UNIT_PUT_IDX), sky2->rx_put);
         return 0;
@@ -1743,15 +1829,6 @@ static void sky2_tx_timeout(struct net_device *dev)
         }
 }
 
-
-/* Want receive buffer size to be multiple of 64 bits
- * and incl room for vlan and truncation
- */
-static inline unsigned sky2_buf_size(int mtu)
-{
-        return ALIGN(mtu + ETH_HLEN + VLAN_HLEN, 8) + 8;
-}
-
 static int sky2_change_mtu(struct net_device *dev, int new_mtu)
 {
         struct sky2_port *sky2 = netdev_priv(dev);
@@ -1786,7 +1863,7 @@ static int sky2_change_mtu(struct net_device *dev, int new_mtu)
         sky2_rx_clean(sky2);
 
         dev->mtu = new_mtu;
-        sky2->rx_bufsize = sky2_buf_size(new_mtu);
+
         mode = DATA_BLIND_VAL(DATA_BLIND_DEF) |
                 GM_SMOD_VLAN_ENA | IPG_DATA_VAL(IPG_DATA_DEF);
 
@@ -1812,9 +1889,93 @@ static int sky2_change_mtu(struct net_device *dev, int new_mtu)
         return err;
 }
 
+/* For small just reuse existing skb for next receive */
+static struct sk_buff *receive_copy(struct sky2_port *sky2,
+                                    const struct rx_ring_info *re,
+                                    unsigned length)
+{
+        struct sk_buff *skb;
+
+        skb = netdev_alloc_skb(sky2->netdev, length + 2);
+        if (likely(skb)) {
+                skb_reserve(skb, 2);
+                pci_dma_sync_single_for_cpu(sky2->hw->pdev, re->data_addr,
+                                            length, PCI_DMA_FROMDEVICE);
+                memcpy(skb->data, re->skb->data, length);
+                skb->ip_summed = re->skb->ip_summed;
+                skb->csum = re->skb->csum;
+                pci_dma_sync_single_for_device(sky2->hw->pdev, re->data_addr,
+                                               length, PCI_DMA_FROMDEVICE);
+                re->skb->ip_summed = CHECKSUM_NONE;
+                __skb_put(skb, length);
+        }
+        return skb;
+}
+
+/* Adjust length of skb with fragments to match received data */
+static void skb_put_frags(struct sk_buff *skb, unsigned int hdr_space,
+                          unsigned int length)
+{
+        int i, num_frags;
+        unsigned int size;
+
+        /* put header into skb */
+        size = min(length, hdr_space);
+        skb->tail += size;
+        skb->len += size;
+        length -= size;
+
+        num_frags = skb_shinfo(skb)->nr_frags;
+        for (i = 0; i < num_frags; i++) {
+                skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+
+                if (length == 0) {
+                        /* don't need this page */
+                        __free_page(frag->page);
+                        --skb_shinfo(skb)->nr_frags;
+                } else {
+                        size = min(length, (unsigned) PAGE_SIZE);
+
+                        frag->size = size;
+                        skb->data_len += size;
+                        skb->truesize += size;
+                        skb->len += size;
+                        length -= size;
+                }
+        }
+}
+
+/* Normal packet - take skb from ring element and put in a new one  */
+static struct sk_buff *receive_new(struct sky2_port *sky2,
+                                   struct rx_ring_info *re,
+                                   unsigned int length)
+{
+        struct sk_buff *skb, *nskb;
+        unsigned hdr_space = sky2->rx_data_size;
+
+        pr_debug(PFX "receive new length=%d\n", length);
+
+        /* Don't be tricky about reusing pages (yet) */
+        nskb = sky2_rx_alloc(sky2);
+        if (unlikely(!nskb))
+                return NULL;
+
+        skb = re->skb;
+        sky2_rx_unmap_skb(sky2->hw->pdev, re);
+
+        prefetch(skb->data);
+        re->skb = nskb;
+        sky2_rx_map_skb(sky2->hw->pdev, re, hdr_space);
+
+        if (skb_shinfo(skb)->nr_frags)
+                skb_put_frags(skb, hdr_space, length);
+        else
+                skb_put(skb, hdr_space);
+        return skb;
+}
+
 /*
  * Receive one packet.
- * For small packets or errors, just reuse existing skb.
  * For larger packets, get new buffer.
  */
 static struct sk_buff *sky2_receive(struct net_device *dev,
@@ -1840,40 +2001,12 @@ static struct sk_buff *sky2_receive(struct net_device *dev,
         if (length > dev->mtu + ETH_HLEN)
                 goto oversize;
 
-        if (length < copybreak) {
-                skb = netdev_alloc_skb(dev, length + 2);
-                if (!skb)
-                        goto resubmit;
-
-                skb_reserve(skb, 2);
-                pci_dma_sync_single_for_cpu(sky2->hw->pdev, re->mapaddr,
-                                            length, PCI_DMA_FROMDEVICE);
-                memcpy(skb->data, re->skb->data, length);
-                skb->ip_summed = re->skb->ip_summed;
-                skb->csum = re->skb->csum;
-                pci_dma_sync_single_for_device(sky2->hw->pdev, re->mapaddr,
-                                               length, PCI_DMA_FROMDEVICE);
-        } else {
-                struct sk_buff *nskb;
-
-                nskb = sky2_alloc_skb(dev, sky2->rx_bufsize, GFP_ATOMIC);
-                if (!nskb)
-                        goto resubmit;
-
-                skb = re->skb;
-                re->skb = nskb;
-                pci_unmap_single(sky2->hw->pdev, re->mapaddr,
-                                 sky2->rx_bufsize, PCI_DMA_FROMDEVICE);
-                prefetch(skb->data);
-
-                re->mapaddr = pci_map_single(sky2->hw->pdev, nskb->data,
-                                         sky2->rx_bufsize, PCI_DMA_FROMDEVICE);
-        }
-
-        skb_put(skb, length);
+        if (length < copybreak)
+                skb = receive_copy(sky2, re, length);
+        else
+                skb = receive_new(sky2, re, length);
 resubmit:
-        re->skb->ip_summed = CHECKSUM_NONE;
-        sky2_rx_add(sky2, re->mapaddr);
+        sky2_rx_submit(sky2, re);
 
         return skb;
 
@@ -3125,7 +3258,6 @@ static __devinit struct net_device *sky2_init_netdev(struct sky2_hw *hw,
         spin_lock_init(&sky2->phy_lock);
         sky2->tx_pending = TX_DEF_PENDING;
         sky2->rx_pending = RX_DEF_PENDING;
-        sky2->rx_bufsize = sky2_buf_size(ETH_DATA_LEN);
 
         hw->dev[port] = dev;
 
diff --git a/drivers/net/sky2.h b/drivers/net/sky2.h
index 403486a3831d..f66109a96d95 100644
--- a/drivers/net/sky2.h
+++ b/drivers/net/sky2.h
@@ -4,6 +4,8 @@
 #ifndef _SKY2_H
 #define _SKY2_H
 
+#define ETH_JUMBO_MTU           9000    /* Maximum MTU supported */
+
 /* PCI device specific config registers */
 enum {
         PCI_DEV_REG1    = 0x40,
@@ -1779,7 +1781,9 @@ struct tx_ring_info {
 
 struct rx_ring_info {
         struct sk_buff  *skb;
-        dma_addr_t      mapaddr;
+        dma_addr_t      data_addr;
+        DECLARE_PCI_UNMAP_ADDR(data_size);
+        dma_addr_t      frag_addr[ETH_JUMBO_MTU >> PAGE_SHIFT];
 };
 
 struct sky2_port {
@@ -1804,7 +1808,9 @@ struct sky2_port {
         u16                  rx_next;           /* next re to check */
         u16                  rx_put;            /* next le index to use */
         u16                  rx_pending;
-        u16                  rx_bufsize;
+        u16                  rx_data_size;
+        u16                  rx_nfrags;
+
 #ifdef SKY2_VLAN_TAG_USED
         u16                  rx_tag;
         struct vlan_group    *vlgrp;