target/linux/generic/pending-5.4/770-09-net-ethernet-mtk_eth_soc-only-read-the-full-rx-descr.patch

   1 From: Felix Fietkau <nbd@nbd.name>
   2 Date: Thu, 27 Aug 2020 09:24:25 +0200
   3 Subject: [PATCH] net: ethernet: mtk_eth_soc: only read the full rx
   4  descriptor if DMA is done
   5
   6 Uncached memory access is expensive, and there is no need to access all
   7 descriptor words if we can't process them anyway
   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 @@ -793,13 +793,18 @@ static inline int mtk_max_buf_size(int f
  15         return buf_size;
  16  }
  17
  18 -static inline void mtk_rx_get_desc(struct mtk_rx_dma *rxd,
  19 +static inline bool mtk_rx_get_desc(struct mtk_rx_dma *rxd,
  20                                    struct mtk_rx_dma *dma_rxd)
  21  {
  22 -       rxd->rxd1 = READ_ONCE(dma_rxd->rxd1);
  23         rxd->rxd2 = READ_ONCE(dma_rxd->rxd2);
  24 +       if (!(rxd->rxd2 & RX_DMA_DONE))
  25 +               return false;
  26 +
  27 +       rxd->rxd1 = READ_ONCE(dma_rxd->rxd1);
  28         rxd->rxd3 = READ_ONCE(dma_rxd->rxd3);
  29         rxd->rxd4 = READ_ONCE(dma_rxd->rxd4);
  30 +
  31 +       return true;
  32  }
  33
  34  /* the qdma core needs scratch memory to be setup */
  35 @@ -1271,8 +1276,7 @@ static int mtk_poll_rx(struct napi_struc
  36                 rxd = &ring->dma[idx];
  37                 data = ring->data[idx];
  38
  39 -               mtk_rx_get_desc(&trxd, rxd);
  40 -               if (!(trxd.rxd2 & RX_DMA_DONE))
  41 +               if (!mtk_rx_get_desc(&trxd, rxd))
  42                         break;
  43
  44                 /* find out which mac the packet come from. values start at 1 */