target/linux/generic/pending-5.4/770-08-net-ethernet-mtk_eth_soc-cache-hardware-pointer-of-l.patch

   1 From: Felix Fietkau <nbd@nbd.name>
   2 Date: Thu, 27 Aug 2020 06:32:03 +0200
   3 Subject: [PATCH] net: ethernet: mtk_eth_soc: cache hardware pointer of last
   4  freed tx descriptor
   5
   6 The value is only updated by the CPU, so it is cheaper to access from the ring
   7 data structure than from a hardware register
   8
   9 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  10 ---
  11
  12 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  13 +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  14 @@ -1358,7 +1358,7 @@ static int mtk_poll_tx_qdma(struct mtk_e
  15         struct mtk_tx_buf *tx_buf;
  16         u32 cpu, dma;
  17
  18 -       cpu = mtk_r32(eth, MTK_QTX_CRX_PTR);
  19 +       cpu = ring->last_free_ptr;
  20         dma = mtk_r32(eth, MTK_QTX_DRX_PTR);
  21
  22         desc = mtk_qdma_phys_to_virt(ring, cpu);
  23 @@ -1392,6 +1392,7 @@ static int mtk_poll_tx_qdma(struct mtk_e
  24                 cpu = next_cpu;
  25         }
  26
  27 +       ring->last_free_ptr = cpu;
  28         mtk_w32(eth, cpu, MTK_QTX_CRX_PTR);
  29
  30         return budget;
  31 @@ -1592,6 +1593,7 @@ static int mtk_tx_alloc(struct mtk_eth *
  32         atomic_set(&ring->free_count, MTK_DMA_SIZE - 2);
  33         ring->next_free = &ring->dma[0];
  34         ring->last_free = &ring->dma[MTK_DMA_SIZE - 1];
  35 +       ring->last_free_ptr = (u32)(ring->phys + ((MTK_DMA_SIZE - 1) * sz));
  36         ring->thresh = MAX_SKB_FRAGS;
  37
  38         /* make sure that all changes to the dma ring are flushed before we
  39 @@ -1605,9 +1607,7 @@ static int mtk_tx_alloc(struct mtk_eth *
  40                 mtk_w32(eth,
  41                         ring->phys + ((MTK_DMA_SIZE - 1) * sz),
  42                         MTK_QTX_CRX_PTR);
  43 -               mtk_w32(eth,
  44 -                       ring->phys + ((MTK_DMA_SIZE - 1) * sz),
  45 -                       MTK_QTX_DRX_PTR);
  46 +               mtk_w32(eth, ring->last_free_ptr, MTK_QTX_DRX_PTR);
  47                 mtk_w32(eth, (QDMA_RES_THRES << 8) | QDMA_RES_THRES,
  48                         MTK_QTX_CFG(0));
  49         } else {
  50 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.h
  51 +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
  52 @@ -622,6 +622,7 @@ struct mtk_tx_buf {
  53   * @phys:              The physical addr of tx_buf
  54   * @next_free:         Pointer to the next free descriptor
  55   * @last_free:         Pointer to the last free descriptor
  56 + * @last_free_ptr:     Hardware pointer value of the last free descriptor
  57   * @thresh:            The threshold of minimum amount of free descriptors
  58   * @free_count:                QDMA uses a linked list. Track how many free descriptors
  59   *                     are present
  60 @@ -632,6 +633,7 @@ struct mtk_tx_ring {
  61         dma_addr_t phys;
  62         struct mtk_tx_dma *next_free;
  63         struct mtk_tx_dma *last_free;
  64 +       u32 last_free_ptr;
  65         u16 thresh;
  66         atomic_t free_count;
  67         int dma_size;