target/linux/ramips/patches-5.4/0401-net-ethernet-mediatek-significantly-reduce-mdio-bus-.patch

   1 From: Felix Fietkau <nbd@nbd.name>
   2 Date: Mon, 8 Jun 2020 17:02:39 +0200
   3 Subject: [PATCH] net: ethernet: mediatek: significantly reduce mdio bus
   4  access latency
   5
   6 usleep_range often ends up sleeping much longer than the 10-20us provided
   7 as a range here. This causes significant latency in mdio bus acceses,
   8 which easily adds multiple seconds to the boot time on MT7621 when polling
   9 DSA slave ports.
  10 Use cond_resched instead of usleep_range, since the MDIO access does not
  11 take much time
  12
  13 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  14 ---
  15
  16 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  17 +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  18 @@ -85,7 +85,7 @@ static int mtk_mdio_busy_wait(struct mtk
  19                         return 0;
  20                 if (time_after(jiffies, t_start + PHY_IAC_TIMEOUT))
  21                         break;
  22 -               usleep_range(10, 20);
  23 +               cond_resched();
  24         }
  25
  26         dev_err(eth->dev, "mdio: MDIO timeout\n");