target/linux/lantiq/patches-5.10/0705-v5.17-net-lantiq_xrx200-add-ingress-SG-DMA-support.patch

   1 From c3e6b2c35b34214c58c1e90d65dab5f5393608e7 Mon Sep 17 00:00:00 2001
   2 From: Aleksander Jan Bajkowski <olek2@wp.pl>
   3 Date: Mon, 3 Jan 2022 20:43:16 +0100
   4 Subject: [PATCH] net: lantiq_xrx200: add ingress SG DMA support
   5
   6 This patch adds support for scatter gather DMA. DMA in PMAC splits
   7 the packet into several buffers when the MTU on the CPU port is
   8 less than the MTU of the switch. The first buffer starts at an
   9 offset of NET_IP_ALIGN. In subsequent buffers, dma ignores the
  10 offset. Thanks to this patch, the user can still connect to the
  11 device in such a situation. For normal configurations, the patch
  12 has no effect on performance.
  13
  14 Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
  15 Signed-off-by: David S. Miller <davem@davemloft.net>
  16 ---
  17  drivers/net/ethernet/lantiq_xrx200.c | 47 +++++++++++++++++++++++-----
  18  1 file changed, 40 insertions(+), 7 deletions(-)
  19
  20 --- a/drivers/net/ethernet/lantiq_xrx200.c
  21 +++ b/drivers/net/ethernet/lantiq_xrx200.c
  22 @@ -26,6 +26,9 @@
  23  #define XRX200_DMA_RX          0
  24  #define XRX200_DMA_TX          1
  25
  26 +#define XRX200_DMA_PACKET_COMPLETE     0
  27 +#define XRX200_DMA_PACKET_IN_PROGRESS  1
  28 +
  29  /* cpu port mac */
  30  #define PMAC_RX_IPG            0x0024
  31  #define PMAC_RX_IPG_MASK       0xf
  32 @@ -61,6 +64,9 @@ struct xrx200_chan {
  33         struct ltq_dma_channel dma;
  34         struct sk_buff *skb[LTQ_DESC_NUM];
  35
  36 +       struct sk_buff *skb_head;
  37 +       struct sk_buff *skb_tail;
  38 +
  39         struct xrx200_priv *priv;
  40  };
  41
  42 @@ -204,7 +210,8 @@ static int xrx200_hw_receive(struct xrx2
  43         struct xrx200_priv *priv = ch->priv;
  44         struct ltq_dma_desc *desc = &ch->dma.desc_base[ch->dma.desc];
  45         struct sk_buff *skb = ch->skb[ch->dma.desc];
  46 -       int len = (desc->ctl & LTQ_DMA_SIZE_MASK);
  47 +       u32 ctl = desc->ctl;
  48 +       int len = (ctl & LTQ_DMA_SIZE_MASK);
  49         struct net_device *net_dev = priv->net_dev;
  50         int ret;
  51
  52 @@ -220,12 +227,36 @@ static int xrx200_hw_receive(struct xrx2
  53         }
  54
  55         skb_put(skb, len);
  56 -       skb->protocol = eth_type_trans(skb, net_dev);
  57 -       netif_receive_skb(skb);
  58 -       net_dev->stats.rx_packets++;
  59 -       net_dev->stats.rx_bytes += len;
  60
  61 -       return 0;
  62 +       /* add buffers to skb via skb->frag_list */
  63 +       if (ctl & LTQ_DMA_SOP) {
  64 +               ch->skb_head = skb;
  65 +               ch->skb_tail = skb;
  66 +       } else if (ch->skb_head) {
  67 +               if (ch->skb_head == ch->skb_tail)
  68 +                       skb_shinfo(ch->skb_tail)->frag_list = skb;
  69 +               else
  70 +                       ch->skb_tail->next = skb;
  71 +               ch->skb_tail = skb;
  72 +               skb_reserve(ch->skb_tail, -NET_IP_ALIGN);
  73 +               ch->skb_head->len += skb->len;
  74 +               ch->skb_head->data_len += skb->len;
  75 +               ch->skb_head->truesize += skb->truesize;
  76 +       }
  77 +
  78 +       if (ctl & LTQ_DMA_EOP) {
  79 +               ch->skb_head->protocol = eth_type_trans(ch->skb_head, net_dev);
  80 +               netif_receive_skb(ch->skb_head);
  81 +               net_dev->stats.rx_packets++;
  82 +               net_dev->stats.rx_bytes += ch->skb_head->len;
  83 +               ch->skb_head = NULL;
  84 +               ch->skb_tail = NULL;
  85 +               ret = XRX200_DMA_PACKET_COMPLETE;
  86 +       } else {
  87 +               ret = XRX200_DMA_PACKET_IN_PROGRESS;
  88 +       }
  89 +
  90 +       return ret;
  91  }
  92
  93  static int xrx200_poll_rx(struct napi_struct *napi, int budget)
  94 @@ -240,7 +271,9 @@ static int xrx200_poll_rx(struct napi_st
  95
  96                 if ((desc->ctl & (LTQ_DMA_OWN | LTQ_DMA_C)) == LTQ_DMA_C) {
  97                         ret = xrx200_hw_receive(ch);
  98 -                       if (ret)
  99 +                       if (ret == XRX200_DMA_PACKET_IN_PROGRESS)
 100 +                               continue;
 101 +                       if (ret != XRX200_DMA_PACKET_COMPLETE)
 102                                 return ret;
 103                         rx++;
 104                 } else {