phy: add support for a reset-gpio specification

The framework only asserts (for now) that the reset gpio is not active.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/phy.txt

@@ -35,11 +35,14 @@ Optional Properties:
 - broken-turn-around: If set, indicates the PHY device does not correctly
   release the turn around line low at the end of a MDIO transaction.
 
+- reset-gpios: Reference to a GPIO used to reset the phy.
+
 Example:
 
 ethernet-phy@0 {
 	compatible = "ethernet-phy-id0141.0e90", "ethernet-phy-ieee802.3-c22";
 	interrupt-parent = <40000>;
 	interrupts = <35 1>;
 	reg = <0>;
+	reset-gpios = <&gpio1 17 GPIO_ACTIVE_LOW>;
 };

drivers/net/phy/phy_device.c

@@ -34,6 +34,7 @@
 #include <linux/io.h>
 #include <linux/uaccess.h>
 #include <linux/of.h>
+#include <linux/gpio/consumer.h>
 
 #include <asm/irq.h>
 
@@ -1570,9 +1571,16 @@ static int phy_probe(struct device *dev)
 	struct device_driver *drv = phydev->mdio.dev.driver;
 	struct phy_driver *phydrv = to_phy_driver(drv);
 	int err = 0;
+	struct gpio_descs *reset_gpios;
 
 	phydev->drv = phydrv;
 
+	/* take phy out of reset */
+	reset_gpios = devm_gpiod_get_array_optional(dev, "reset",
+						    GPIOD_OUT_LOW);
+	if (IS_ERR(reset_gpios))
+		return PTR_ERR(reset_gpios);
+
 	/* Disable the interrupt if the PHY doesn't support it
 	 * but the interrupt is still a valid one
 	 */