atl1c: improve link detection reliability on Mikrotik 10/25G NIC

Mikrotik 10/25G NIC emulates the MDIO accesses, but the emulation is
not 100% reliable - the MDIO ops occasionally can timeout.

This adds a reliable way of detecting link on Mikrotik 10/25G NIC.
Signed-off-by: Gatis Peisenieks <gatis@mikrotik.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/atheros/atl1c/atl1c_hw.c

@@ -636,6 +636,23 @@ int atl1c_phy_init(struct atl1c_hw *hw)
 	return 0;
 }
 
+bool atl1c_get_link_status(struct atl1c_hw *hw)
+{
+	u16 phy_data;
+
+	if (hw->nic_type == athr_mt) {
+		u32 spd;
+
+		AT_READ_REG(hw, REG_MT_SPEED, &spd);
+		return !!spd;
+	}
+
+	/* MII_BMSR must be read twice */
+	atl1c_read_phy_reg(hw, MII_BMSR, &phy_data);
+	atl1c_read_phy_reg(hw, MII_BMSR, &phy_data);
+	return !!(phy_data & BMSR_LSTATUS);
+}
+
 /*
  * Detects the current speed and duplex settings of the hardware.
  *
@@ -695,15 +712,12 @@ int atl1c_phy_to_ps_link(struct atl1c_hw *hw)
 	int ret = 0;
 	u16 autoneg_advertised = ADVERTISED_10baseT_Half;
 	u16 save_autoneg_advertised;
-	u16 phy_data;
 	u16 mii_lpa_data;
 	u16 speed = SPEED_0;
 	u16 duplex = FULL_DUPLEX;
 	int i;
 
-	atl1c_read_phy_reg(hw, MII_BMSR, &phy_data);
-	atl1c_read_phy_reg(hw, MII_BMSR, &phy_data);
-	if (phy_data & BMSR_LSTATUS) {
+	if (atl1c_get_link_status(hw)) {
 		atl1c_read_phy_reg(hw, MII_LPA, &mii_lpa_data);
 		if (mii_lpa_data & LPA_10FULL)
 			autoneg_advertised = ADVERTISED_10baseT_Full;
@@ -726,9 +740,7 @@ int atl1c_phy_to_ps_link(struct atl1c_hw *hw)
 		if (mii_lpa_data) {
 			for (i = 0; i < AT_SUSPEND_LINK_TIMEOUT; i++) {
 				mdelay(100);
-				atl1c_read_phy_reg(hw, MII_BMSR, &phy_data);
-				atl1c_read_phy_reg(hw, MII_BMSR, &phy_data);
-				if (phy_data & BMSR_LSTATUS) {
+				if (atl1c_get_link_status(hw)) {
 					if (atl1c_get_speed_and_duplex(hw, &speed,
 									&duplex) != 0)
 						dev_dbg(&pdev->dev,

drivers/net/ethernet/atheros/atl1c/atl1c_hw.h

@@ -26,6 +26,7 @@ void atl1c_phy_disable(struct atl1c_hw *hw);
 void atl1c_hw_set_mac_addr(struct atl1c_hw *hw, u8 *mac_addr);
 int atl1c_phy_reset(struct atl1c_hw *hw);
 int atl1c_read_mac_addr(struct atl1c_hw *hw);
+bool atl1c_get_link_status(struct atl1c_hw *hw);
 int atl1c_get_speed_and_duplex(struct atl1c_hw *hw, u16 *speed, u16 *duplex);
 u32 atl1c_hash_mc_addr(struct atl1c_hw *hw, u8 *mc_addr);
 void atl1c_hash_set(struct atl1c_hw *hw, u32 hash_value);

drivers/net/ethernet/atheros/atl1c/atl1c_main.c

@@ -232,15 +232,14 @@ static void atl1c_check_link_status(struct atl1c_adapter *adapter)
 	struct pci_dev    *pdev   = adapter->pdev;
 	int err;
 	unsigned long flags;
-	u16 speed, duplex, phy_data;
+	u16 speed, duplex;
+	bool link;
 
 	spin_lock_irqsave(&adapter->mdio_lock, flags);
-	/* MII_BMSR must read twise */
-	atl1c_read_phy_reg(hw, MII_BMSR, &phy_data);
-	atl1c_read_phy_reg(hw, MII_BMSR, &phy_data);
+	link = atl1c_get_link_status(hw);
 	spin_unlock_irqrestore(&adapter->mdio_lock, flags);
 
-	if ((phy_data & BMSR_LSTATUS) == 0) {
+	if (!link) {
 		/* link down */
 		netif_carrier_off(netdev);
 		hw->hibernate = true;
@@ -284,16 +283,13 @@ static void atl1c_link_chg_event(struct atl1c_adapter *adapter)
 {
 	struct net_device *netdev = adapter->netdev;
 	struct pci_dev    *pdev   = adapter->pdev;
-	u16 phy_data;
-	u16 link_up;
+	bool link;
 
 	spin_lock(&adapter->mdio_lock);
-	atl1c_read_phy_reg(&adapter->hw, MII_BMSR, &phy_data);
-	atl1c_read_phy_reg(&adapter->hw, MII_BMSR, &phy_data);
+	link = atl1c_get_link_status(&adapter->hw);
 	spin_unlock(&adapter->mdio_lock);
-	link_up = phy_data & BMSR_LSTATUS;
 	/* notify upper layer link down ASAP */
-	if (!link_up) {
+	if (!link) {
 		if (netif_carrier_ok(netdev)) {
 			/* old link state: Up */
 			netif_carrier_off(netdev);