phy: exynos-usb2: add vbus regulator support

Exynos USB2 PHY has separate power supply, which is usually provided by
VBUS regulator. This patch adds support for it. VBUS regulator is
optional, to keep compatibility with boards, which have VBUS provided
from some always-on power source.

Signed-off-by: Marek Szyprowski <[e-mail]>
Tested-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Kishon Vijay Abraham I <[e-mail]>

Documentation/devicetree/bindings/phy/samsung-phy.txt

···
 	- the "ref" clock is used to get the rate of the clock provided to the
 	  PHY module
 
+Optional properties:
+- vbus-supply: power-supply phandle for vbus power source
+
 The first phandle argument in the PHY specifier identifies the PHY, its
 meaning is compatible dependent. For the currently supported SoCs (Exynos 4210
 and Exynos 4212) it is as follows:

drivers/phy/phy-samsung-usb2.c

···
 
 	dev_dbg(drv->dev, "Request to power_on \"%s\" usb phy\n",
 		inst->cfg->label);
+
+	if (drv->vbus) {
+		ret = regulator_enable(drv->vbus);
+		if (ret)
+			goto err_regulator;
+	}
+
 	ret = clk_prepare_enable(drv->clk);
 	if (ret)
 		goto err_main_clk;
···
 err_instance_clk:
 	clk_disable_unprepare(drv->clk);
 err_main_clk:
+	if (drv->vbus)
+		regulator_disable(drv->vbus);
+err_regulator:
 	return ret;
 }
 
···
 {
 	struct samsung_usb2_phy_instance *inst = phy_get_drvdata(phy);
 	struct samsung_usb2_phy_driver *drv = inst->drv;
-	int ret;
+	int ret = 0;
 
 	dev_dbg(drv->dev, "Request to power_off \"%s\" usb phy\n",
 		inst->cfg->label);
···
 	}
 	clk_disable_unprepare(drv->ref_clk);
 	clk_disable_unprepare(drv->clk);
-	return 0;
+	if (drv->vbus)
+		ret = regulator_disable(drv->vbus);
+
+	return ret;
 }
 
 static const struct phy_ops samsung_usb2_phy_ops = {
···
 		ret = drv->cfg->rate_to_clk(drv->ref_rate, &drv->ref_reg_val);
 		if (ret)
 			return ret;
+	}
+
+	drv->vbus = devm_regulator_get(dev, "vbus");
+	if (IS_ERR(drv->vbus)) {
+		ret = PTR_ERR(drv->vbus);
+		if (ret == -EPROBE_DEFER)
+			return ret;
+		drv->vbus = NULL;
 	}
 
 	for (i = 0; i < drv->cfg->num_phys; i++) {

drivers/phy/phy-samsung-usb2.h

···
 #include <linux/device.h>
 #include <linux/regmap.h>
 #include <linux/spinlock.h>
+#include <linux/regulator/consumer.h>
 
 #define KHZ 1000
 #define MHZ (KHZ * KHZ)
···
 	const struct samsung_usb2_phy_config *cfg;
 	struct clk *clk;
 	struct clk *ref_clk;
+	struct regulator *vbus;
 	unsigned long ref_rate;
 	u32 ref_reg_val;
 	struct device *dev;