target/linux/generic/backport-5.10/610-v5.13-41-net-ethernet-mtk_eth_soc-reduce-MDIO-bus-access-late.patch

   1 From 3630d519d7c3eab92567658690e44ffe0517d109 Mon Sep 17 00:00:00 2001
   2 From: Felix Fietkau <nbd@nbd.name>
   3 Date: Thu, 22 Apr 2021 22:20:58 -0700
   4 Subject: [PATCH] net: ethernet: mtk_eth_soc: reduce MDIO bus 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 Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>
  15 Signed-off-by: David S. Miller <davem@davemloft.net>
  16 ---
  17  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 2 +-
  18  1 file changed, 1 insertion(+), 1 deletion(-)
  19
  20 --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  21 +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
  22 @@ -86,7 +86,7 @@ static int mtk_mdio_busy_wait(struct mtk
  23                         return 0;
  24                 if (time_after(jiffies, t_start + PHY_IAC_TIMEOUT))
  25                         break;
  26 -               usleep_range(10, 20);
  27 +               cond_resched();
  28         }
  29
  30         dev_err(eth->dev, "mdio: MDIO timeout\n");