usb: phy: msm: Add D+/D- lines route control

apq8016-sbc board is using Dual SPDT USB Switch (TC7USB40MU),
witch is controlled by GPIO to de/multiplex D+/D- USB lines to
USB2513B Hub and uB connector. Add support for this.

Signed-off-by: Ivan T. Ivanov <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

Documentation/devicetree/bindings/usb/msm-hsusb.txt

···
 Optional properties:
 - dr_mode:      One of "host", "peripheral" or "otg". Defaults to "otg"
 
+- switch-gpio:  A phandle + gpio-specifier pair. Some boards are using Dual
+                SPDT USB Switch, witch is cotrolled by GPIO to de/multiplex
+                D+/D- USB lines between connectors.
+
 - qcom,phy-init-sequence: PHY configuration sequence values. This is related to Device
                 Mode Eye Diagram test. Start address at which these values will be
                 written is ULPI_EXT_VENDOR_SPECIFIC. Value of -1 is reserved as

drivers/usb/phy/phy-msm-usb.c

···
 
 #include <linux/module.h>
 #include <linux/device.h>
+#include <linux/gpio/consumer.h>
 #include <linux/platform_device.h>
 #include <linux/clk.h>
 #include <linux/slab.h>
···
 #include <linux/pm_runtime.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
+#include <linux/reboot.h>
 #include <linux/reset.h>
 
 #include <linux/usb.h>
···
 	else
 		clear_bit(B_SESS_VLD, &motg->inputs);
 
+	if (test_bit(B_SESS_VLD, &motg->inputs)) {
+		/* Switch D+/D- lines to Device connector */
+		gpiod_set_value_cansleep(motg->switch_gpio, 0);
+	} else {
+		/* Switch D+/D- lines to Hub */
+		gpiod_set_value_cansleep(motg->switch_gpio, 1);
+	}
+
 	schedule_work(&motg->sm_work);
 
 	return NOTIFY_DONE;
···
 
 	motg->manual_pullup = of_property_read_bool(node, "qcom,manual-pullup");
 
+	motg->switch_gpio = devm_gpiod_get_optional(&pdev->dev, "switch",
+						    GPIOD_OUT_LOW);
+	if (IS_ERR(motg->switch_gpio))
+		return PTR_ERR(motg->switch_gpio);
+
 	ext_id = ERR_PTR(-ENODEV);
 	ext_vbus = ERR_PTR(-ENODEV);
 	if (of_property_read_bool(node, "extcon")) {
···
 		pdata->phy_init_sz = words;
 
 	return 0;
+}
+
+static int msm_otg_reboot_notify(struct notifier_block *this,
+				 unsigned long code, void *unused)
+{
+	struct msm_otg *motg = container_of(this, struct msm_otg, reboot);
+
+	/*
+	 * Ensure that D+/D- lines are routed to uB connector, so
+	 * we could load bootloader/kernel at next reboot
+	 */
+	gpiod_set_value_cansleep(motg->switch_gpio, 0);
+	return NOTIFY_DONE;
 }
 
 static int msm_otg_probe(struct platform_device *pdev)
···
 			dev_dbg(&pdev->dev, "Can not create mode change file\n");
 	}
 
+	if (test_bit(B_SESS_VLD, &motg->inputs)) {
+		/* Switch D+/D- lines to Device connector */
+		gpiod_set_value_cansleep(motg->switch_gpio, 0);
+	} else {
+		/* Switch D+/D- lines to Hub */
+		gpiod_set_value_cansleep(motg->switch_gpio, 1);
+	}
+
+	motg->reboot.notifier_call = msm_otg_reboot_notify;
+	register_reboot_notifier(&motg->reboot);
+
 	pm_runtime_set_active(&pdev->dev);
 	pm_runtime_enable(&pdev->dev);
 
···
 
 	if (phy->otg->host || phy->otg->gadget)
 		return -EBUSY;
+
+	unregister_reboot_notifier(&motg->reboot);
+
+	/*
+	 * Ensure that D+/D- lines are routed to uB connector, so
+	 * we could load bootloader/kernel at next reboot
+	 */
+	gpiod_set_value_cansleep(motg->switch_gpio, 0);
 
 	extcon_unregister_notifier(motg->id.extcon, EXTCON_USB_HOST, &motg->id.nb);
 	extcon_unregister_notifier(motg->vbus.extcon, EXTCON_USB, &motg->vbus.nb);

include/linux/usb/msm_hsusb.h

···
  *	starting controller using usbcmd run/stop bit.
  * @vbus: VBUS signal state trakining, using extcon framework
  * @id: ID signal state trakining, using extcon framework
+ * @switch_gpio: Descriptor for GPIO used to control external Dual
+ *               SPDT USB Switch.
+ * @reboot: Used to inform the driver to route USB D+/D- line to Device
+ *	    connector
  */
 struct msm_otg {
 	struct usb_phy phy;
···
 
 	struct msm_usb_cable vbus;
 	struct msm_usb_cable id;
+
+	struct gpio_desc *switch_gpio;
+	struct notifier_block reboot;
 };
 
 #endif