target/linux/mediatek/patches-4.4/0071-net-mediatek-fix-TX-locking.patch

   1 From b9df14f712866925856c0ffb2d899511c21e1b8a Mon Sep 17 00:00:00 2001
   2 From: John Crispin <blogic@openwrt.org>
   3 Date: Tue, 29 Mar 2016 17:20:01 +0200
   4 Subject: [PATCH 71/78] net: mediatek: fix TX locking
   5
   6 Inside the TX path there is a lock inside the tx_map function. This is
   7 however too late. The patch moves the lock to the start of the xmit
   8 function right before the free count check of the DMA ring happens.
   9 If we do not do this, the code becomes racy leading to TX stalls and
  10 dropped packets. This happens as there are 2 netdevs running on the
  11 same physical DMA ring.
  12
  13 Signed-off-by: John Crispin <blogic@openwrt.org>
  14 ---
  15  drivers/net/ethernet/mediatek/mtk_eth_soc.c |   20 ++++++++++----------
  16  1 file changed, 10 insertions(+), 10 deletions(-)
  17
  18 diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  19 index 26eeb1a..67b18f9 100644
  20 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  21 +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  22 @@ -536,7 +536,6 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
  23         struct mtk_eth *eth = mac->hw;
  24         struct mtk_tx_dma *itxd, *txd;
  25         struct mtk_tx_buf *tx_buf;
  26 -       unsigned long flags;
  27         dma_addr_t mapped_addr;
  28         unsigned int nr_frags;
  29         int i, n_desc = 1;
  30 @@ -568,11 +567,6 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
  31         if (unlikely(dma_mapping_error(&dev->dev, mapped_addr)))
  32                 return -ENOMEM;
  33
  34 -       /* normally we can rely on the stack not calling this more than once,
  35 -        * however we have 2 queues running ont he same ring so we need to lock
  36 -        * the ring access
  37 -        */
  38 -       spin_lock_irqsave(&eth->page_lock, flags);
  39         WRITE_ONCE(itxd->txd1, mapped_addr);
  40         tx_buf->flags |= MTK_TX_FLAGS_SINGLE0;
  41         dma_unmap_addr_set(tx_buf, dma_addr0, mapped_addr);
  42 @@ -632,8 +626,6 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
  43         WRITE_ONCE(itxd->txd3, (TX_DMA_SWC | TX_DMA_PLEN0(skb_headlen(skb)) |
  44                                 (!nr_frags * TX_DMA_LS0)));
  45
  46 -       spin_unlock_irqrestore(&eth->page_lock, flags);
  47 -
  48         netdev_sent_queue(dev, skb->len);
  49         skb_tx_timestamp(skb);
  50
  51 @@ -661,8 +653,6 @@ err_dma:
  52                 itxd = mtk_qdma_phys_to_virt(ring, itxd->txd2);
  53         } while (itxd != txd);
  54
  55 -       spin_unlock_irqrestore(&eth->page_lock, flags);
  56 -
  57         return -ENOMEM;
  58  }
  59
  60 @@ -712,14 +702,22 @@ static int mtk_start_xmit(struct sk_buff *skb, struct net_device *dev)
  61         struct mtk_eth *eth = mac->hw;
  62         struct mtk_tx_ring *ring = &eth->tx_ring;
  63         struct net_device_stats *stats = &dev->stats;
  64 +       unsigned long flags;
  65         bool gso = false;
  66         int tx_num;
  67
  68 +       /* normally we can rely on the stack not calling this more than once,
  69 +        * however we have 2 queues running ont he same ring so we need to lock
  70 +        * the ring access
  71 +        */
  72 +       spin_lock_irqsave(&eth->page_lock, flags);
  73 +
  74         tx_num = mtk_cal_txd_req(skb);
  75         if (unlikely(atomic_read(&ring->free_count) <= tx_num)) {
  76                 mtk_stop_queue(eth);
  77                 netif_err(eth, tx_queued, dev,
  78                           "Tx Ring full when queue awake!\n");
  79 +               spin_unlock_irqrestore(&eth->page_lock, flags);
  80                 return NETDEV_TX_BUSY;
  81         }
  82
  83 @@ -747,10 +745,12 @@ static int mtk_start_xmit(struct sk_buff *skb, struct net_device *dev)
  84                              ring->thresh))
  85                         mtk_wake_queue(eth);
  86         }
  87 +       spin_unlock_irqrestore(&eth->page_lock, flags);
  88
  89         return NETDEV_TX_OK;
  90
  91  drop:
  92 +       spin_unlock_irqrestore(&eth->page_lock, flags);
  93         stats->tx_dropped++;
  94         dev_kfree_skb(skb);
  95         return NETDEV_TX_OK;
  96 --
  97 1.7.10.4
  98