phy: rockchip-usb: Add vbus regulator support.

On rockchip devices vbus is supplied by a separate power supply, often
through a regulator. Add support for describing the the regulator in
device-tree following the same convention as several other usb phy's.
Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

Documentation/devicetree/bindings/phy/rockchip-usb-phy.txt

@@ -30,6 +30,7 @@ Optional Properties:
 - reset-names: Only allow the following entries:
  - phy-reset
 - resets: Must contain an entry for each entry in reset-names.
+- vbus-supply: power-supply phandle for vbus power source
 
 Example:
 

drivers/phy/phy-rockchip-usb.c

@@ -66,6 +66,7 @@ struct rockchip_usb_phy {
 	struct phy	*phy;
 	bool		uart_enabled;
 	struct reset_control *reset;
+	struct regulator *vbus;
 };
 
 static int rockchip_usb_phy_power(struct rockchip_usb_phy *phy,
@@ -88,6 +89,9 @@ static void rockchip_usb_phy480m_disable(struct clk_hw *hw)
 						    struct rockchip_usb_phy,
 						    clk480m_hw);
 
+	if (phy->vbus)
+		regulator_disable(phy->vbus);
+
 	/* Power down usb phy analog blocks by set siddq 1 */
 	rockchip_usb_phy_power(phy, 1);
 }
@@ -143,6 +147,14 @@ static int rockchip_usb_phy_power_on(struct phy *_phy)
 	if (phy->uart_enabled)
 		return -EBUSY;
 
+	if (phy->vbus) {
+		int ret;
+
+		ret = regulator_enable(phy->vbus);
+		if (ret)
+			return ret;
+	}
+
 	return clk_prepare_enable(phy->clk480m);
 }
 
@@ -268,6 +280,13 @@ static int rockchip_usb_phy_init(struct rockchip_usb_phy_base *base,
 	}
 	phy_set_drvdata(rk_phy->phy, rk_phy);
 
+	rk_phy->vbus = devm_regulator_get_optional(&rk_phy->phy->dev, "vbus");
+	if (IS_ERR(rk_phy->vbus)) {
+		if (PTR_ERR(rk_phy->vbus) == -EPROBE_DEFER)
+			return PTR_ERR(rk_phy->vbus);
+		rk_phy->vbus = NULL;
+	}
+
 	/*
 	 * When acting as uart-pipe, just keep clock on otherwise
 	 * only power up usb phy when it use, so disable it when init