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-rw-r--r--target/linux/mediatek/patches-4.4/0071-net-mediatek-fix-TX-locking.patch98
1 files changed, 98 insertions, 0 deletions
diff --git a/target/linux/mediatek/patches-4.4/0071-net-mediatek-fix-TX-locking.patch b/target/linux/mediatek/patches-4.4/0071-net-mediatek-fix-TX-locking.patch
new file mode 100644
index 0000000000..011fad2e61
--- /dev/null
+++ b/target/linux/mediatek/patches-4.4/0071-net-mediatek-fix-TX-locking.patch
@@ -0,0 +1,98 @@
+From b9df14f712866925856c0ffb2d899511c21e1b8a Mon Sep 17 00:00:00 2001
+From: John Crispin <blogic@openwrt.org>
+Date: Tue, 29 Mar 2016 17:20:01 +0200
+Subject: [PATCH 71/78] net: mediatek: fix TX locking
+
+Inside the TX path there is a lock inside the tx_map function. This is
+however too late. The patch moves the lock to the start of the xmit
+function right before the free count check of the DMA ring happens.
+If we do not do this, the code becomes racy leading to TX stalls and
+dropped packets. This happens as there are 2 netdevs running on the
+same physical DMA ring.
+
+Signed-off-by: John Crispin <blogic@openwrt.org>
+---
+ drivers/net/ethernet/mediatek/mtk_eth_soc.c | 20 ++++++++++----------
+ 1 file changed, 10 insertions(+), 10 deletions(-)
+
+diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+index 26eeb1a..67b18f9 100644
+--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
++++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+@@ -536,7 +536,6 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
+ struct mtk_eth *eth = mac->hw;
+ struct mtk_tx_dma *itxd, *txd;
+ struct mtk_tx_buf *tx_buf;
+- unsigned long flags;
+ dma_addr_t mapped_addr;
+ unsigned int nr_frags;
+ int i, n_desc = 1;
+@@ -568,11 +567,6 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
+ if (unlikely(dma_mapping_error(&dev->dev, mapped_addr)))
+ return -ENOMEM;
+
+- /* normally we can rely on the stack not calling this more than once,
+- * however we have 2 queues running ont he same ring so we need to lock
+- * the ring access
+- */
+- spin_lock_irqsave(&eth->page_lock, flags);
+ WRITE_ONCE(itxd->txd1, mapped_addr);
+ tx_buf->flags |= MTK_TX_FLAGS_SINGLE0;
+ dma_unmap_addr_set(tx_buf, dma_addr0, mapped_addr);
+@@ -632,8 +626,6 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
+ WRITE_ONCE(itxd->txd3, (TX_DMA_SWC | TX_DMA_PLEN0(skb_headlen(skb)) |
+ (!nr_frags * TX_DMA_LS0)));
+
+- spin_unlock_irqrestore(&eth->page_lock, flags);
+-
+ netdev_sent_queue(dev, skb->len);
+ skb_tx_timestamp(skb);
+
+@@ -661,8 +653,6 @@ err_dma:
+ itxd = mtk_qdma_phys_to_virt(ring, itxd->txd2);
+ } while (itxd != txd);
+
+- spin_unlock_irqrestore(&eth->page_lock, flags);
+-
+ return -ENOMEM;
+ }
+
+@@ -712,14 +702,22 @@ static int mtk_start_xmit(struct sk_buff *skb, struct net_device *dev)
+ struct mtk_eth *eth = mac->hw;
+ struct mtk_tx_ring *ring = &eth->tx_ring;
+ struct net_device_stats *stats = &dev->stats;
++ unsigned long flags;
+ bool gso = false;
+ int tx_num;
+
++ /* normally we can rely on the stack not calling this more than once,
++ * however we have 2 queues running ont he same ring so we need to lock
++ * the ring access
++ */
++ spin_lock_irqsave(&eth->page_lock, flags);
++
+ tx_num = mtk_cal_txd_req(skb);
+ if (unlikely(atomic_read(&ring->free_count) <= tx_num)) {
+ mtk_stop_queue(eth);
+ netif_err(eth, tx_queued, dev,
+ "Tx Ring full when queue awake!\n");
++ spin_unlock_irqrestore(&eth->page_lock, flags);
+ return NETDEV_TX_BUSY;
+ }
+
+@@ -747,10 +745,12 @@ static int mtk_start_xmit(struct sk_buff *skb, struct net_device *dev)
+ ring->thresh))
+ mtk_wake_queue(eth);
+ }
++ spin_unlock_irqrestore(&eth->page_lock, flags);
+
+ return NETDEV_TX_OK;
+
+ drop:
++ spin_unlock_irqrestore(&eth->page_lock, flags);
+ stats->tx_dropped++;
+ dev_kfree_skb(skb);
+ return NETDEV_TX_OK;
+--
+1.7.10.4
+