target/linux/generic/backport-5.10/610-v5.13-47-net-ethernet-mtk_eth_soc-only-read-the-full-RX-descr.patch

   1 From 816ac3e6e67bdd78d86226c6eb53619780750e92 Mon Sep 17 00:00:00 2001
   2 From: Felix Fietkau <nbd@nbd.name>
   3 Date: Thu, 22 Apr 2021 22:21:04 -0700
   4 Subject: [PATCH] net: ethernet: mtk_eth_soc: only read the full RX descriptor
   5  if DMA is done
   6
   7 Uncached memory access is expensive, and there is no need to access all
   8 descriptor words if we can't process them anyway
   9
  10 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  11 Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>
  12 Signed-off-by: David S. Miller <davem@davemloft.net>
  13 ---
  14  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 12 ++++++++----
  15  1 file changed, 8 insertions(+), 4 deletions(-)
  16
  17 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  18 +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  19 @@ -799,13 +799,18 @@ static inline int mtk_max_buf_size(int f
  20         return buf_size;
  21  }
  22
  23 -static inline void mtk_rx_get_desc(struct mtk_rx_dma *rxd,
  24 +static inline bool mtk_rx_get_desc(struct mtk_rx_dma *rxd,
  25                                    struct mtk_rx_dma *dma_rxd)
  26  {
  27 -       rxd->rxd1 = READ_ONCE(dma_rxd->rxd1);
  28         rxd->rxd2 = READ_ONCE(dma_rxd->rxd2);
  29 +       if (!(rxd->rxd2 & RX_DMA_DONE))
  30 +               return false;
  31 +
  32 +       rxd->rxd1 = READ_ONCE(dma_rxd->rxd1);
  33         rxd->rxd3 = READ_ONCE(dma_rxd->rxd3);
  34         rxd->rxd4 = READ_ONCE(dma_rxd->rxd4);
  35 +
  36 +       return true;
  37  }
  38
  39  static void *mtk_max_lro_buf_alloc(gfp_t gfp_mask)
  40 @@ -1288,8 +1293,7 @@ static int mtk_poll_rx(struct napi_struc
  41                 rxd = &ring->dma[idx];
  42                 data = ring->data[idx];
  43
  44 -               mtk_rx_get_desc(&trxd, rxd);
  45 -               if (!(trxd.rxd2 & RX_DMA_DONE))
  46 +               if (!mtk_rx_get_desc(&trxd, rxd))
  47                         break;
  48
  49                 /* find out which mac the packet come from. values start at 1 */