openwrt/target/linux/generic/backport-5.10/735-v5.14-17-net-dsa-qca8k-clear-MASTER_EN-after-phy-read-write.patch

From 63c33bbfeb6842a956a0eb12901e28eb335bdb18 Mon Sep 17 00:00:00 2001
From: Ansuel Smith <[email protected]>
Date: Fri, 14 May 2021 23:00:07 +0200
Subject: [PATCH] net: dsa: qca8k: clear MASTER_EN after phy read/write

Clear MDIO_MASTER_EN bit from MDIO_MASTER_CTRL after read/write
operation. The MDIO_MASTER_EN bit is not reset after read/write
operation and the next operation can be wrongly interpreted by the
switch as a mdio operation. This cause a production of wrong/garbage
data from the switch and underfined bheavior. (random port drop,
unplugged port flagged with link up, wrong port speed)
Also on driver remove the MASTER_CTRL can be left set and cause the
malfunction of any next driver using the mdio device.

Signed-off-by: Ansuel Smith <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
---
 drivers/net/dsa/qca8k.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

--- a/drivers/net/dsa/qca8k.c
+++ b/drivers/net/dsa/qca8k.c
@@ -649,8 +649,14 @@ qca8k_mdio_write(struct qca8k_priv *priv
 	if (ret)
 		return ret;
 
-	return qca8k_busy_wait(priv, QCA8K_MDIO_MASTER_CTRL,
-		QCA8K_MDIO_MASTER_BUSY);
+	ret = qca8k_busy_wait(priv, QCA8K_MDIO_MASTER_CTRL,
+			      QCA8K_MDIO_MASTER_BUSY);
+
+	/* even if the busy_wait timeouts try to clear the MASTER_EN */
+	qca8k_reg_clear(priv, QCA8K_MDIO_MASTER_CTRL,
+			QCA8K_MDIO_MASTER_EN);
+
+	return ret;
 }
 
 static int
@@ -685,6 +691,10 @@ qca8k_mdio_read(struct qca8k_priv *priv,
 
 	val &= QCA8K_MDIO_MASTER_DATA_MASK;
 
+	/* even if the busy_wait timeouts try to clear the MASTER_EN */
+	qca8k_reg_clear(priv, QCA8K_MDIO_MASTER_CTRL,
+			QCA8K_MDIO_MASTER_EN);
+
 	return val;
 }