From: Felix Fietkau <nbd@nbd.name>
Date: Fri, 23 Apr 2021 05:20:58 +0000 (-0700)
Subject: net: ethernet: mtk_eth_soc: reduce MDIO bus access latency
X-Git-Tag: v5.15~1236^2~57^2~10
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=3630d519d7c3eab92567658690e44ffe0517d109;p=platform%2Fkernel%2Flinux-starfive.git

net: ethernet: mtk_eth_soc: reduce MDIO bus access latency

usleep_range often ends up sleeping much longer than the 10-20us provided
as a range here. This causes significant latency in mdio bus acceses,
which easily adds multiple seconds to the boot time on MT7621 when polling
DSA slave ports.
Use cond_resched instead of usleep_range, since the MDIO access does not
take much time

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index 5cf64de..d992d4f 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -86,7 +86,7 @@ static int mtk_mdio_busy_wait(struct mtk_eth *eth)
 			return 0;
 		if (time_after(jiffies, t_start + PHY_IAC_TIMEOUT))
 			break;
-		usleep_range(10, 20);
+		cond_resched();
 	}
 
 	dev_err(eth->dev, "mdio: MDIO timeout\n");