[PATCH] net: phy: micrel: Do not overwrite reserved bits

[Sascha Hauer]

ksz8021_config_init() unconditionally sets the KSZPHY_OMSO_RMII_OVERRIDE
bit. This is since the initial micrel phy commit, so it's not
reproducible where this comes from and why this is done. Neither U-Boot
nor the kernel ever touch this bit and so should we. Also, instead
of doing a write only operation, read/modify/write the bit we actually
want to change.
This fixes operation on a KSZ8081MLX which is a MII only phy.
KSZPHY_OMSO_RMII_OVERRIDE is reserved here and must be written to 0.
KSZPHY_OMSO_MII_OVERRIDE is default 1 and must be written as 1.

Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 drivers/net/phy/micrel.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index 9a30cb7..0ca359b 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -72,8 +72,12 @@ static int kszphy_config_init(struct phy_device *phydev)
 
 static int ksz8021_config_init(struct phy_device *phydev)
 {
-	const u16 val = KSZPHY_OMSO_B_CAST_OFF | KSZPHY_OMSO_RMII_OVERRIDE;
+	u16 val;
+
+	val = phy_read(phydev, MII_KSZPHY_OMSO);
+	val |= KSZPHY_OMSO_B_CAST_OFF;
 	phy_write(phydev, MII_KSZPHY_OMSO, val);
+
 	return 0;
 }
 
-- 
2.10.1