net: hns3: fix phy can not link up when autoneg off and reset

Currently, function hclge_mdio_read() will return 0 if during reset(the
cmd state will be set to disable).

If use general phy driver, the phy_state_machine() will update phy speed
every second in function genphy_read_status_fixed() when PHY is set to
autoneg off, no matter of link down or link up.

If phy driver happens to read BMCR register during reset, phy speed will
be updated to 10Mpbs as BMCR register value is 0. So it may call phy can
not link up if previous speed is not 10Mpbs.

To fix this problem, function hclge_mdio_read() should return -EBUSY if
the cmd state is disable. So does function hclge_mdio_write().

Fixes: 1c12493 ("net: hns3: bugfix for hclge_mdio_write and hclge_mdio_read")
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Guangbin Huang

drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_mdio.c

@@ -48,7 +48,7 @@ static int hclge_mdio_write(struct mii_bus *bus, int phyid, int regnum,
 	int ret;
 
 	if (test_bit(HCLGE_COMM_STATE_CMD_DISABLE, &hdev->hw.hw.comm_state))
-		return 0;
+		return -EBUSY;
 
 	hclge_cmd_setup_basic_desc(&desc, HCLGE_OPC_MDIO_CONFIG, false);
 
@@ -86,7 +86,7 @@ static int hclge_mdio_read(struct mii_bus *bus, int phyid, int regnum)
 	int ret;
 
 	if (test_bit(HCLGE_COMM_STATE_CMD_DISABLE, &hdev->hw.hw.comm_state))
-		return 0;
+		return -EBUSY;
 
 	hclge_cmd_setup_basic_desc(&desc, HCLGE_OPC_MDIO_CONFIG, true);