target/linux/generic/pending-6.6/732-01-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 @@ -26,6 +26,7 @@
  20  #include <linux/bitfield.h>
  21  #include <net/dsa.h>
  22  #include <net/dst_metadata.h>
  23 +#include <net/gso.h>
  24  #include <net/page_pool/helpers.h>
  25
  26  #include "mtk_eth_soc.h"
  27 @@ -1562,12 +1562,28 @@ static void mtk_wake_queue(struct mtk_et
  28         }
  29  }
  30
  31 +static bool mtk_skb_has_small_frag(struct sk_buff *skb)
  32 +{
  33 +       int min_size = 16;
  34 +       int i;
  35 +
  36 +       if (skb_headlen(skb) < min_size)
  37 +               return true;
  38 +
  39 +       for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
  40 +               if (skb_frag_size(&skb_shinfo(skb)->frags[i]) < min_size)
  41 +                       return true;
  42 +
  43 +       return false;
  44 +}
  45 +
  46  static netdev_tx_t mtk_start_xmit(struct sk_buff *skb, struct net_device *dev)
  47  {
  48         struct mtk_mac *mac = netdev_priv(dev);
  49         struct mtk_eth *eth = mac->hw;
  50         struct mtk_tx_ring *ring = &eth->tx_ring;
  51         struct net_device_stats *stats = &dev->stats;
  52 +       struct sk_buff *segs, *next;
  53         bool gso = false;
  54         int tx_num;
  55
  56 @@ -1589,6 +1605,18 @@ static netdev_tx_t mtk_start_xmit(struct
  57                 return NETDEV_TX_BUSY;
  58         }
  59
  60 +       if (mtk_is_netsys_v1(eth) &&
  61 +           skb_is_gso(skb) && mtk_skb_has_small_frag(skb)) {
  62 +               segs = skb_gso_segment(skb, dev->features & ~NETIF_F_ALL_TSO);
  63 +               if (IS_ERR(segs))
  64 +                       goto drop;
  65 +
  66 +               if (segs) {
  67 +                       consume_skb(skb);
  68 +                       skb = segs;
  69 +               }
  70 +       }
  71 +
  72         /* TSO: fill MSS info in tcp checksum field */
  73         if (skb_is_gso(skb)) {
  74                 if (skb_cow_head(skb, 0)) {
  75 @@ -1604,8 +1632,14 @@ static netdev_tx_t mtk_start_xmit(struct
  76                 }
  77         }
  78
  79 -       if (mtk_tx_map(skb, dev, tx_num, ring, gso) < 0)
  80 -               goto drop;
  81 +       skb_list_walk_safe(skb, skb, next) {
  82 +               if ((mtk_is_netsys_v1(eth) &&
  83 +                    mtk_skb_has_small_frag(skb) && skb_linearize(skb)) ||
  84 +                   mtk_tx_map(skb, dev, tx_num, ring, gso) < 0) {
  85 +                               stats->tx_dropped++;
  86 +                               dev_kfree_skb_any(skb);
  87 +               }
  88 +       }
  89
  90         if (unlikely(atomic_read(&ring->free_count) <= ring->thresh))
  91                 netif_tx_stop_all_queues(dev);
  92 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.h
  93 +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
  94 @@ -268,7 +268,7 @@
  95  #define MTK_CHK_DDONE_EN       BIT(28)
  96  #define MTK_DMAD_WR_WDONE      BIT(26)
  97  #define MTK_WCOMP_EN           BIT(24)
  98 -#define MTK_RESV_BUF           (0x40 << 16)
  99 +#define MTK_RESV_BUF           (0x80 << 16)
 100  #define MTK_MUTLI_CNT          (0x4 << 12)
 101  #define MTK_LEAKY_BUCKET_EN    BIT(11)
 102