target/linux/generic/patches-3.18/077-04-bgmac-simplify-tx-ring-index-handling.patch

   1 From: Felix Fietkau <nbd@openwrt.org>
   2 Date: Sun, 12 Apr 2015 09:58:56 +0200
   3 Subject: [PATCH] bgmac: simplify tx ring index handling
   4
   5 Keep incrementing ring->start and ring->end instead of pointing it to
   6 the actual ring slot entry. This simplifies the calculation of the
   7 number of free slots.
   8
   9 Signed-off-by: Felix Fietkau <nbd@openwrt.org>
  10 ---
  11
  12 --- a/drivers/net/ethernet/broadcom/bgmac.c
  13 +++ b/drivers/net/ethernet/broadcom/bgmac.c
  14 @@ -142,11 +142,10 @@ static netdev_tx_t bgmac_dma_tx_add(stru
  15  {
  16         struct device *dma_dev = bgmac->core->dma_dev;
  17         struct net_device *net_dev = bgmac->net_dev;
  18 -       struct bgmac_slot_info *slot = &ring->slots[ring->end];
  19 -       int free_slots;
  20 +       int index = ring->end % BGMAC_TX_RING_SLOTS;
  21 +       struct bgmac_slot_info *slot = &ring->slots[index];
  22         int nr_frags;
  23         u32 flags;
  24 -       int index = ring->end;
  25         int i;
  26
  27         if (skb->len > BGMAC_DESC_CTL1_LEN) {
  28 @@ -158,13 +157,7 @@ static netdev_tx_t bgmac_dma_tx_add(stru
  29                 skb_checksum_help(skb);
  30
  31         nr_frags = skb_shinfo(skb)->nr_frags;
  32 -
  33 -       if (ring->start <= ring->end)
  34 -               free_slots = ring->start - ring->end + BGMAC_TX_RING_SLOTS;
  35 -       else
  36 -               free_slots = ring->start - ring->end;
  37 -
  38 -       if (free_slots <= nr_frags + 1) {
  39 +       if (ring->end - ring->start + nr_frags + 1 >= BGMAC_TX_RING_SLOTS) {
  40                 bgmac_err(bgmac, "TX ring is full, queue should be stopped!\n");
  41                 netif_stop_queue(net_dev);
  42                 return NETDEV_TX_BUSY;
  43 @@ -200,7 +193,7 @@ static netdev_tx_t bgmac_dma_tx_add(stru
  44         }
  45
  46         slot->skb = skb;
  47 -
  48 +       ring->end += nr_frags + 1;
  49         netdev_sent_queue(net_dev, skb->len);
  50
  51         wmb();
  52 @@ -208,13 +201,12 @@ static netdev_tx_t bgmac_dma_tx_add(stru
  53         /* Increase ring->end to point empty slot. We tell hardware the first
  54          * slot it should *not* read.
  55          */
  56 -       ring->end = (index + 1) % BGMAC_TX_RING_SLOTS;
  57         bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_TX_INDEX,
  58                     ring->index_base +
  59 -                   ring->end * sizeof(struct bgmac_dma_desc));
  60 +                   (ring->end % BGMAC_TX_RING_SLOTS) *
  61 +                   sizeof(struct bgmac_dma_desc));
  62
  63 -       free_slots -= nr_frags + 1;
  64 -       if (free_slots < 8)
  65 +       if (ring->end - ring->start >= BGMAC_TX_RING_SLOTS - 8)
  66                 netif_stop_queue(net_dev);
  67
  68         return NETDEV_TX_OK;
  69 @@ -256,17 +248,17 @@ static void bgmac_dma_tx_free(struct bgm
  70         empty_slot &= BGMAC_DMA_TX_STATDPTR;
  71         empty_slot /= sizeof(struct bgmac_dma_desc);
  72
  73 -       while (ring->start != empty_slot) {
  74 -               struct bgmac_slot_info *slot = &ring->slots[ring->start];
  75 -               u32 ctl1 = le32_to_cpu(ring->cpu_base[ring->start].ctl1);
  76 -               int len = ctl1 & BGMAC_DESC_CTL1_LEN;
  77 +       while (ring->start != ring->end) {
  78 +               int slot_idx = ring->start % BGMAC_TX_RING_SLOTS;
  79 +               struct bgmac_slot_info *slot = &ring->slots[slot_idx];
  80 +               u32 ctl1;
  81 +               int len;
  82
  83 -               if (!slot->dma_addr) {
  84 -                       bgmac_err(bgmac, "Hardware reported transmission for empty TX ring slot %d! End of ring: %d\n",
  85 -                                 ring->start, ring->end);
  86 -                       goto next;
  87 -               }
  88 +               if (slot_idx == empty_slot)
  89 +                       break;
  90
  91 +               ctl1 = le32_to_cpu(ring->cpu_base[slot_idx].ctl1);
  92 +               len = ctl1 & BGMAC_DESC_CTL1_LEN;
  93                 if (ctl1 & BGMAC_DESC_CTL0_SOF)
  94                         /* Unmap no longer used buffer */
  95                         dma_unmap_single(dma_dev, slot->dma_addr, len,
  96 @@ -284,10 +276,8 @@ static void bgmac_dma_tx_free(struct bgm
  97                         slot->skb = NULL;
  98                 }
  99
 100 -next:
 101                 slot->dma_addr = 0;
 102 -               if (++ring->start >= BGMAC_TX_RING_SLOTS)
 103 -                       ring->start = 0;
 104 +               ring->start++;
 105                 freed = true;
 106         }
 107
 108 --- a/drivers/net/ethernet/broadcom/bgmac.h
 109 +++ b/drivers/net/ethernet/broadcom/bgmac.h
 110 @@ -414,10 +414,10 @@ enum bgmac_dma_ring_type {
 111   * empty.
 112   */
 113  struct bgmac_dma_ring {
 114 -       u16 num_slots;
 115 -       u16 start;
 116 -       u16 end;
 117 +       u32 start;
 118 +       u32 end;
 119
 120 +       u16 num_slots;
 121         u16 mmio_base;
 122         struct bgmac_dma_desc *cpu_base;
 123         dma_addr_t dma_base;