net: phy: dp83867: add workaround for incorrect RX_CTRL pin strap

The data manual for DP83867IR/CR, SNLS484E[1], revised march 2017,
advises that strapping RX_DV/RX_CTRL pin in mode 1 and 2 is not
supported (see note below Table 5 (4-Level Strap Pins)).

There are some boards which have the pin strapped this way and need
software workaround suggested by the data manual. Bit[7] of
Configuration Register 4 (address 0x0031) must be cleared to 0. This
ensures proper operation of the PHY.

Implement driver support for device-tree property meant to advertise
the wrong strapping.

[1] http://www.ti.com/lit/ds/snls484e/snls484e.pdf

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
[nsekhar@ti.com: rebase to mainline, code simplification]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/dp83867.c

@@ -91,6 +91,7 @@ struct dp83867_private {
 	int fifo_depth;
 	int io_impedance;
 	int port_mirroring;
+	bool rxctrl_strap_quirk;
 };
 
 static int dp83867_ack_interrupt(struct phy_device *phydev)
@@ -164,6 +165,9 @@ static int dp83867_of_init(struct phy_device *phydev)
 	else if (of_property_read_bool(of_node, "ti,min-output-impedance"))
 		dp83867->io_impedance = DP83867_IO_MUX_CFG_IO_IMPEDANCE_MIN;
 
+	dp83867->rxctrl_strap_quirk = of_property_read_bool(of_node,
+					"ti,dp83867-rxctrl-strap-quirk");
+
 	ret = of_property_read_u32(of_node, "ti,rx-internal-delay",
 				   &dp83867->rx_id_delay);
 	if (ret &&
@@ -214,6 +218,13 @@ static int dp83867_config_init(struct phy_device *phydev)
 		dp83867 = (struct dp83867_private *)phydev->priv;
 	}
 
+	/* RX_DV/RX_CTRL strapped in mode 1 or mode 2 workaround */
+	if (dp83867->rxctrl_strap_quirk) {
+		val = phy_read_mmd(phydev, DP83867_DEVADDR, DP83867_CFG4);
+		val &= ~BIT(7);
+		phy_write_mmd(phydev, DP83867_DEVADDR, DP83867_CFG4, val);
+	}
+
 	if (phy_interface_is_rgmii(phydev)) {
 		val = phy_read(phydev, MII_DP83867_PHYCTRL);
 		if (val < 0)