Adds support for ethtool PHY loopback selftest. It uses
genphy_loopback function, which use BMCR loopback bit to
enable or disable loopback.

Signed-off-by: Raju Rangoju <Raju.Rangoju@amd.com>
---
 drivers/net/ethernet/amd/xgbe/xgbe-selftest.c | 40 +++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-selftest.c b/drivers/net/ethernet/amd/xgbe/xgbe-selftest.c
index b8d1de07d570..927c7aed7e4a 100644
--- a/drivers/net/ethernet/amd/xgbe/xgbe-selftest.c
+++ b/drivers/net/ethernet/amd/xgbe/xgbe-selftest.c
@@ -23,6 +23,7 @@
 
 #define XGBE_LOOPBACK_NONE	0
 #define XGBE_LOOPBACK_MAC	1
+#define XGBE_LOOPBACK_PHY	2
 
 struct xgbe_hdr {
 	__be32 version;
@@ -307,11 +308,36 @@ static int xgbe_test_mac_loopback(struct xgbe_prv_data *pdata)
 	return __xgbe_test_loopback(pdata, &attr);
 }
 
+static int xgbe_test_phy_loopback(struct xgbe_prv_data *pdata)
+{
+	struct xgbe_pkt_attrs attr = {};
+	int ret;
+
+	if (!pdata->netdev->phydev) {
+		netdev_err(pdata->netdev, "phydev not found: cannot start PHY loopback test\n");
+		return -EOPNOTSUPP;
+	}
+
+	ret = phy_loopback(pdata->netdev->phydev, true, 0);
+	if (ret)
+		return ret;
+
+	attr.dst = pdata->netdev->dev_addr;
+	ret = __xgbe_test_loopback(pdata, &attr);
+
+	phy_loopback(pdata->netdev->phydev, false, 0);
+	return ret;
+}
+
 static const struct xgbe_test xgbe_selftests[] = {
 	{
 		.name = "MAC Loopback               ",
 		.lb = XGBE_LOOPBACK_MAC,
 		.fn = xgbe_test_mac_loopback,
+	}, {
+		.name = "PHY Loopback               ",
+		.lb = XGBE_LOOPBACK_NONE,
+		.fn = xgbe_test_phy_loopback,
 	},
 };
 
@@ -343,6 +369,13 @@ void xgbe_selftest_run(struct net_device *dev,
 		ret = 0;
 
 		switch (xgbe_selftests[i].lb) {
+		case XGBE_LOOPBACK_PHY:
+			ret = -EOPNOTSUPP;
+			if (dev->phydev)
+				ret = phy_loopback(dev->phydev, true, 0);
+			if (!ret)
+				break;
+			fallthrough;
 		case XGBE_LOOPBACK_MAC:
 			ret = xgbe_config_mac_loopback(pdata, true);
 			break;
@@ -369,6 +402,13 @@ void xgbe_selftest_run(struct net_device *dev,
 		buf[i] = ret;
 
 		switch (xgbe_selftests[i].lb) {
+		case XGBE_LOOPBACK_PHY:
+			ret = -EOPNOTSUPP;
+			if (dev->phydev)
+				ret = phy_loopback(dev->phydev, false, 0);
+			if (!ret)
+				break;
+			fallthrough;
 		case XGBE_LOOPBACK_MAC:
 			xgbe_config_mac_loopback(pdata, false);
 			break;
-- 
2.34.1