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

   1 From: Felix Fietkau <nbd@nbd.name>
   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@nbd.name>
  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 @@ -159,12 +158,10 @@ static netdev_tx_t bgmac_dma_tx_add(stru
  29
  30         nr_frags = skb_shinfo(skb)->nr_frags;
  31
  32 -       if (ring->start <= ring->end)
  33 -               free_slots = ring->start - ring->end + BGMAC_TX_RING_SLOTS;
  34 -       else
  35 -               free_slots = ring->start - ring->end;
  36 -
  37 -       if (free_slots <= nr_frags + 1) {
  38 +       /* ring->end - ring->start will return the number of valid slots,
  39 +        * even when ring->end overflows
  40 +        */
  41 +       if (ring->end - ring->start + nr_frags + 1 >= BGMAC_TX_RING_SLOTS) {
  42                 bgmac_err(bgmac, "TX ring is full, queue should be stopped!\n");
  43                 netif_stop_queue(net_dev);
  44                 return NETDEV_TX_BUSY;
  45 @@ -200,7 +197,7 @@ static netdev_tx_t bgmac_dma_tx_add(stru
  46         }
  47
  48         slot->skb = skb;
  49 -
  50 +       ring->end += nr_frags + 1;
  51         netdev_sent_queue(net_dev, skb->len);
  52
  53         wmb();
  54 @@ -208,13 +205,12 @@ static netdev_tx_t bgmac_dma_tx_add(stru
  55         /* Increase ring->end to point empty slot. We tell hardware the first
  56          * slot it should *not* read.
  57          */
  58 -       ring->end = (index + 1) % BGMAC_TX_RING_SLOTS;
  59         bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_TX_INDEX,
  60                     ring->index_base +
  61 -                   ring->end * sizeof(struct bgmac_dma_desc));
  62 +                   (ring->end % BGMAC_TX_RING_SLOTS) *
  63 +                   sizeof(struct bgmac_dma_desc));
  64
  65 -       free_slots -= nr_frags + 1;
  66 -       if (free_slots < 8)
  67 +       if (ring->end - ring->start >= BGMAC_TX_RING_SLOTS - 8)
  68                 netif_stop_queue(net_dev);
  69
  70         return NETDEV_TX_OK;
  71 @@ -256,17 +252,17 @@ static void bgmac_dma_tx_free(struct bgm
  72         empty_slot &= BGMAC_DMA_TX_STATDPTR;
  73         empty_slot /= sizeof(struct bgmac_dma_desc);
  74
  75 -       while (ring->start != empty_slot) {
  76 -               struct bgmac_slot_info *slot = &ring->slots[ring->start];
  77 -               u32 ctl1 = le32_to_cpu(ring->cpu_base[ring->start].ctl1);
  78 -               int len = ctl1 & BGMAC_DESC_CTL1_LEN;
  79 +       while (ring->start != ring->end) {
  80 +               int slot_idx = ring->start % BGMAC_TX_RING_SLOTS;
  81 +               struct bgmac_slot_info *slot = &ring->slots[slot_idx];
  82 +               u32 ctl1;
  83 +               int len;
  84
  85 -               if (!slot->dma_addr) {
  86 -                       bgmac_err(bgmac, "Hardware reported transmission for empty TX ring slot %d! End of ring: %d\n",
  87 -                                 ring->start, ring->end);
  88 -                       goto next;
  89 -               }
  90 +               if (slot_idx == empty_slot)
  91 +                       break;
  92
  93 +               ctl1 = le32_to_cpu(ring->cpu_base[slot_idx].ctl1);
  94 +               len = ctl1 & BGMAC_DESC_CTL1_LEN;
  95                 if (ctl1 & BGMAC_DESC_CTL0_SOF)
  96                         /* Unmap no longer used buffer */
  97                         dma_unmap_single(dma_dev, slot->dma_addr, len,
  98 @@ -284,10 +280,8 @@ static void bgmac_dma_tx_free(struct bgm
  99                         slot->skb = NULL;
 100                 }
 101
 102 -next:
 103                 slot->dma_addr = 0;
 104 -               if (++ring->start >= BGMAC_TX_RING_SLOTS)
 105 -                       ring->start = 0;
 106 +               ring->start++;
 107                 freed = true;
 108         }
 109
 110 --- a/drivers/net/ethernet/broadcom/bgmac.h
 111 +++ b/drivers/net/ethernet/broadcom/bgmac.h
 112 @@ -414,10 +414,10 @@ enum bgmac_dma_ring_type {
 113   * empty.
 114   */
 115  struct bgmac_dma_ring {
 116 -       u16 num_slots;
 117 -       u16 start;
 118 -       u16 end;
 119 +       u32 start;
 120 +       u32 end;
 121
 122 +       u16 num_slots;
 123         u16 mmio_base;
 124         struct bgmac_dma_desc *cpu_base;
 125         dma_addr_t dma_base;