bgmac: implement scatter/gather support

Always use software checksumming, since the hardware does not have any
checksum offload support.
This significantly improves local TCP tx performance.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 121 insertions, 43 deletions

diff --git a/drivers/net/ethernet/broadcom/bgmac.c b/drivers/net/ethernet/broadcom/bgmac.c
index c7da37aef035..fa8f9e147c34 100644
--- a/drivers/net/ethernet/broadcom/bgmac.c
+++ b/drivers/net/ethernet/broadcom/bgmac.c
@@ -115,53 +115,91 @@ static void bgmac_dma_tx_enable(struct bgmac *bgmac,
         bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_TX_CTL, ctl);
 }
 
+static void
+bgmac_dma_tx_add_buf(struct bgmac *bgmac, struct bgmac_dma_ring *ring,
+                     int i, int len, u32 ctl0)
+{
+        struct bgmac_slot_info *slot;
+        struct bgmac_dma_desc *dma_desc;
+        u32 ctl1;
+
+        if (i == ring->num_slots - 1)
+                ctl0 |= BGMAC_DESC_CTL0_EOT;
+
+        ctl1 = len & BGMAC_DESC_CTL1_LEN;
+
+        slot = &ring->slots[i];
+        dma_desc = &ring->cpu_base[i];
+        dma_desc->addr_low = cpu_to_le32(lower_32_bits(slot->dma_addr));
+        dma_desc->addr_high = cpu_to_le32(upper_32_bits(slot->dma_addr));
+        dma_desc->ctl0 = cpu_to_le32(ctl0);
+        dma_desc->ctl1 = cpu_to_le32(ctl1);
+}
+
 static netdev_tx_t bgmac_dma_tx_add(struct bgmac *bgmac,
                                     struct bgmac_dma_ring *ring,
                                     struct sk_buff *skb)
 {
         struct device *dma_dev = bgmac->core->dma_dev;
         struct net_device *net_dev = bgmac->net_dev;
-        struct bgmac_dma_desc *dma_desc;
-        struct bgmac_slot_info *slot;
-        u32 ctl0, ctl1;
+        struct bgmac_slot_info *slot = &ring->slots[ring->end];
         int free_slots;
+        int nr_frags;
+        u32 flags;
+        int index = ring->end;
+        int i;
 
         if (skb->len > BGMAC_DESC_CTL1_LEN) {
                 bgmac_err(bgmac, "Too long skb (%d)\n", skb->len);
-                goto err_stop_drop;
+                goto err_drop;
         }
 
+        if (skb->ip_summed == CHECKSUM_PARTIAL)
+                skb_checksum_help(skb);
+
+        nr_frags = skb_shinfo(skb)->nr_frags;
+
         if (ring->start <= ring->end)
                 free_slots = ring->start - ring->end + BGMAC_TX_RING_SLOTS;
         else
                 free_slots = ring->start - ring->end;
-        if (free_slots == 1) {
+
+        if (free_slots <= nr_frags + 1) {
                 bgmac_err(bgmac, "TX ring is full, queue should be stopped!\n");
                 netif_stop_queue(net_dev);
                 return NETDEV_TX_BUSY;
         }
 
-        slot = &ring->slots[ring->end];
-        slot->skb = skb;
-        slot->dma_addr = dma_map_single(dma_dev, skb->data, skb->len,
+        slot->dma_addr = dma_map_single(dma_dev, skb->data, skb_headlen(skb),
                                         DMA_TO_DEVICE);
-        if (dma_mapping_error(dma_dev, slot->dma_addr)) {
-                bgmac_err(bgmac, "Mapping error of skb on ring 0x%X\n",
-                          ring->mmio_base);
-                goto err_stop_drop;
-        }
+        if (unlikely(dma_mapping_error(dma_dev, slot->dma_addr)))
+                goto err_dma_head;
 
-        ctl0 = BGMAC_DESC_CTL0_IOC | BGMAC_DESC_CTL0_SOF | BGMAC_DESC_CTL0_EOF;
-        if (ring->end == ring->num_slots - 1)
-                ctl0 |= BGMAC_DESC_CTL0_EOT;
-        ctl1 = skb->len & BGMAC_DESC_CTL1_LEN;
+        flags = BGMAC_DESC_CTL0_SOF;
+        if (!nr_frags)
+                flags |= BGMAC_DESC_CTL0_EOF | BGMAC_DESC_CTL0_IOC;
 
-        dma_desc = ring->cpu_base;
-        dma_desc += ring->end;
-        dma_desc->addr_low = cpu_to_le32(lower_32_bits(slot->dma_addr));
-        dma_desc->addr_high = cpu_to_le32(upper_32_bits(slot->dma_addr));
-        dma_desc->ctl0 = cpu_to_le32(ctl0);
-        dma_desc->ctl1 = cpu_to_le32(ctl1);
+        bgmac_dma_tx_add_buf(bgmac, ring, index, skb_headlen(skb), flags);
+        flags = 0;
+
+        for (i = 0; i < nr_frags; i++) {
+                struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[i];
+                int len = skb_frag_size(frag);
+
+                index = (index + 1) % BGMAC_TX_RING_SLOTS;
+                slot = &ring->slots[index];
+                slot->dma_addr = skb_frag_dma_map(dma_dev, frag, 0,
+                                                  len, DMA_TO_DEVICE);
+                if (unlikely(dma_mapping_error(dma_dev, slot->dma_addr)))
+                        goto err_dma;
+
+                if (i == nr_frags - 1)
+                        flags |= BGMAC_DESC_CTL0_EOF | BGMAC_DESC_CTL0_IOC;
+
+                bgmac_dma_tx_add_buf(bgmac, ring, index, len, flags);
+        }
+
+        slot->skb = skb;
 
         netdev_sent_queue(net_dev, skb->len);
 
@@ -170,20 +208,35 @@ static netdev_tx_t bgmac_dma_tx_add(struct bgmac *bgmac,
         /* Increase ring->end to point empty slot. We tell hardware the first
          * slot it should *not* read.
          */
-        if (++ring->end >= BGMAC_TX_RING_SLOTS)
-                ring->end = 0;
+        ring->end = (index + 1) % BGMAC_TX_RING_SLOTS;
         bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_TX_INDEX,
                     ring->index_base +
                     ring->end * sizeof(struct bgmac_dma_desc));
 
-        /* Always keep one slot free to allow detecting bugged calls. */
-        if (--free_slots == 1)
+        free_slots -= nr_frags + 1;
+        if (free_slots < 8)
                 netif_stop_queue(net_dev);
 
         return NETDEV_TX_OK;
 
-err_stop_drop:
-        netif_stop_queue(net_dev);
+err_dma:
+        dma_unmap_single(dma_dev, slot->dma_addr, skb_headlen(skb),
+                         DMA_TO_DEVICE);
+
+        while (i > 0) {
+                int index = (ring->end + i) % BGMAC_TX_RING_SLOTS;
+                struct bgmac_slot_info *slot = &ring->slots[index];
+                u32 ctl1 = le32_to_cpu(ring->cpu_base[index].ctl1);
+                int len = ctl1 & BGMAC_DESC_CTL1_LEN;
+
+                dma_unmap_page(dma_dev, slot->dma_addr, len, DMA_TO_DEVICE);
+        }
+
+err_dma_head:
+        bgmac_err(bgmac, "Mapping error of skb on ring 0x%X\n",
+                  ring->mmio_base);
+
+err_drop:
         dev_kfree_skb(skb);
         return NETDEV_TX_OK;
 }
@@ -205,32 +258,45 @@ static void bgmac_dma_tx_free(struct bgmac *bgmac, struct bgmac_dma_ring *ring)
 
         while (ring->start != empty_slot) {
                 struct bgmac_slot_info *slot = &ring->slots[ring->start];
+                u32 ctl1 = le32_to_cpu(ring->cpu_base[ring->start].ctl1);
+                int len = ctl1 & BGMAC_DESC_CTL1_LEN;
 
-                if (slot->skb) {
+                if (!slot->dma_addr) {
+                        bgmac_err(bgmac, "Hardware reported transmission for empty TX ring slot %d! End of ring: %d\n",
+                                  ring->start, ring->end);
+                        goto next;
+                }
+
+                if (ctl1 & BGMAC_DESC_CTL0_SOF)
                         /* Unmap no longer used buffer */
-                        dma_unmap_single(dma_dev, slot->dma_addr,
-                                         slot->skb->len, DMA_TO_DEVICE);
-                        slot->dma_addr = 0;
+                        dma_unmap_single(dma_dev, slot->dma_addr, len,
+                                         DMA_TO_DEVICE);
+                else
+                        dma_unmap_page(dma_dev, slot->dma_addr, len,
+                                       DMA_TO_DEVICE);
 
+                if (slot->skb) {
                         bytes_compl += slot->skb->len;
                         pkts_compl++;
 
                         /* Free memory! :) */
                         dev_kfree_skb(slot->skb);
                         slot->skb = NULL;
-                } else {
-                        bgmac_err(bgmac, "Hardware reported transmission for empty TX ring slot %d! End of ring: %d\n",
-                                  ring->start, ring->end);
                 }
 
+next:
+                slot->dma_addr = 0;
                 if (++ring->start >= BGMAC_TX_RING_SLOTS)
                         ring->start = 0;
                 freed = true;
         }
 
+        if (!pkts_compl)
+                return;
+
         netdev_completed_queue(bgmac->net_dev, pkts_compl, bytes_compl);
 
-        if (freed && netif_queue_stopped(bgmac->net_dev))
+        if (netif_queue_stopped(bgmac->net_dev))
                 netif_wake_queue(bgmac->net_dev);
 }
 
@@ -439,17 +505,25 @@ static void bgmac_dma_tx_ring_free(struct bgmac *bgmac,
                                    struct bgmac_dma_ring *ring)
 {
         struct device *dma_dev = bgmac->core->dma_dev;
+        struct bgmac_dma_desc *dma_desc = ring->cpu_base;
         struct bgmac_slot_info *slot;
         int i;
 
         for (i = 0; i < ring->num_slots; i++) {
+                int len = dma_desc[i].ctl1 & BGMAC_DESC_CTL1_LEN;
+
                 slot = &ring->slots[i];
-                if (slot->skb) {
-                        if (slot->dma_addr)
-                                dma_unmap_single(dma_dev, slot->dma_addr,
-                                                 slot->skb->len, DMA_TO_DEVICE);
-                        dev_kfree_skb(slot->skb);
-                }
+                dev_kfree_skb(slot->skb);
+
+                if (!slot->dma_addr)
+                        continue;
+
+                if (slot->skb)
+                        dma_unmap_single(dma_dev, slot->dma_addr,
+                                         len, DMA_TO_DEVICE);
+                else
+                        dma_unmap_page(dma_dev, slot->dma_addr,
+                                       len, DMA_TO_DEVICE);
         }
 }
 
@@ -1583,6 +1657,10 @@ static int bgmac_probe(struct bcma_device *core)
                 goto err_dma_free;
         }
 
+        net_dev->features = NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM;
+        net_dev->hw_features = net_dev->features;
+        net_dev->vlan_features = net_dev->features;
+
         err = register_netdev(bgmac->net_dev);
         if (err) {
                 bgmac_err(bgmac, "Cannot register net device\n");