[PATCH 4.4 166/268] dp83640: Ensure against premature access to PHY registers after reset

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Esben Haabendal <eha@xxxxxxxx>

[ Upstream commit 76327a35caabd1a932e83d6a42b967aa08584e5d ]

The datasheet specifies a 3uS pause after performing a software
reset. The default implementation of genphy_soft_reset() does not
provide this, so implement soft_reset with the needed pause.

Signed-off-by: Esben Haabendal <eha@xxxxxxxx>
Reviewed-by: Andrew Lunn <andrew@xxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/phy/dp83640.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

--- a/drivers/net/phy/dp83640.c
+++ b/drivers/net/phy/dp83640.c
@@ -1203,6 +1203,23 @@ static void dp83640_remove(struct phy_de
 	kfree(dp83640);
 }
 
+static int dp83640_soft_reset(struct phy_device *phydev)
+{
+	int ret;
+
+	ret = genphy_soft_reset(phydev);
+	if (ret < 0)
+		return ret;
+
+	/* From DP83640 datasheet: "Software driver code must wait 3 us
+	 * following a software reset before allowing further serial MII
+	 * operations with the DP83640."
+	 */
+	udelay(10);		/* Taking udelay inaccuracy into account */
+
+	return 0;
+}
+
 static int dp83640_config_init(struct phy_device *phydev)
 {
 	struct dp83640_private *dp83640 = phydev->priv;
@@ -1496,6 +1513,7 @@ static struct phy_driver dp83640_driver
 	.flags		= PHY_HAS_INTERRUPT,
 	.probe		= dp83640_probe,
 	.remove		= dp83640_remove,
+	.soft_reset	= dp83640_soft_reset,
 	.config_init	= dp83640_config_init,
 	.config_aneg	= genphy_config_aneg,
 	.read_status	= genphy_read_status,