target/linux/generic/pending-5.15/732-01-net-ethernet-mtk_eth_soc-work-around-issue-with-send.patch

   1 From: Felix Fietkau <nbd@nbd.name>
   2 Date: Thu, 3 Nov 2022 12:38:49 +0100
   3 Subject: [PATCH] net: ethernet: mtk_eth_soc: work around issue with sending
   4  small fragments
   5
   6 When lots of frames are sent with a number of very small fragments, an
   7 internal FIFO can overflow, causing the DMA engine to lock up lock up and
   8 transmit attempts time out.
   9
  10 Fix this on MT7986 by increasing the reserved FIFO space.
  11 Fix this on older chips by detecting the presence of small fragments and use
  12 skb_gso_segment + skb_linearize to deal with them.
  13
  14 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  15 ---
  16
  17 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  18 +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  19 @@ -1517,12 +1517,28 @@ static void mtk_wake_queue(struct mtk_et
  20         }
  21  }
  22
  23 +static bool mtk_skb_has_small_frag(struct sk_buff *skb)
  24 +{
  25 +       int min_size = 16;
  26 +       int i;
  27 +
  28 +       if (skb_headlen(skb) < min_size)
  29 +               return true;
  30 +
  31 +       for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
  32 +               if (skb_frag_size(&skb_shinfo(skb)->frags[i]) < min_size)
  33 +                       return true;
  34 +
  35 +       return false;
  36 +}
  37 +
  38  static netdev_tx_t mtk_start_xmit(struct sk_buff *skb, struct net_device *dev)
  39  {
  40         struct mtk_mac *mac = netdev_priv(dev);
  41         struct mtk_eth *eth = mac->hw;
  42         struct mtk_tx_ring *ring = &eth->tx_ring;
  43         struct net_device_stats *stats = &dev->stats;
  44 +       struct sk_buff *segs, *next;
  45         bool gso = false;
  46         int tx_num;
  47
  48 @@ -1544,6 +1560,18 @@ static netdev_tx_t mtk_start_xmit(struct
  49                 return NETDEV_TX_BUSY;
  50         }
  51
  52 +       if (mtk_is_netsys_v1(eth) &&
  53 +           skb_is_gso(skb) && mtk_skb_has_small_frag(skb)) {
  54 +               segs = skb_gso_segment(skb, dev->features & ~NETIF_F_ALL_TSO);
  55 +               if (IS_ERR(segs))
  56 +                       goto drop;
  57 +
  58 +               if (segs) {
  59 +                       consume_skb(skb);
  60 +                       skb = segs;
  61 +               }
  62 +       }
  63 +
  64         /* TSO: fill MSS info in tcp checksum field */
  65         if (skb_is_gso(skb)) {
  66                 if (skb_cow_head(skb, 0)) {
  67 @@ -1559,8 +1587,14 @@ static netdev_tx_t mtk_start_xmit(struct
  68                 }
  69         }
  70
  71 -       if (mtk_tx_map(skb, dev, tx_num, ring, gso) < 0)
  72 -               goto drop;
  73 +       skb_list_walk_safe(skb, skb, next) {
  74 +               if ((mtk_is_netsys_v1(eth) &&
  75 +                    mtk_skb_has_small_frag(skb) && skb_linearize(skb)) ||
  76 +                   mtk_tx_map(skb, dev, tx_num, ring, gso) < 0) {
  77 +                               stats->tx_dropped++;
  78 +                               dev_kfree_skb_any(skb);
  79 +               }
  80 +       }
  81
  82         if (unlikely(atomic_read(&ring->free_count) <= ring->thresh))
  83                 netif_tx_stop_all_queues(dev);
  84 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.h
  85 +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
  86 @@ -268,7 +268,7 @@
  87  #define MTK_CHK_DDONE_EN       BIT(28)
  88  #define MTK_DMAD_WR_WDONE      BIT(26)
  89  #define MTK_WCOMP_EN           BIT(24)
  90 -#define MTK_RESV_BUF           (0x40 << 16)
  91 +#define MTK_RESV_BUF           (0x80 << 16)
  92  #define MTK_MUTLI_CNT          (0x4 << 12)
  93  #define MTK_LEAKY_BUCKET_EN    BIT(11)
  94