Merge "USB: Allow skipping device resume during system resume"

drivers/usb/core/driver.c

@@ -1441,6 +1441,9 @@ int usb_suspend(struct device *dev, pm_message_t msg)
 {
 	struct usb_device	*udev = to_usb_device(dev);
 
+	if (udev->bus->skip_resume && udev->state == USB_STATE_SUSPENDED)
+		return 0;
+
 	unbind_no_pm_drivers_interfaces(udev);
 
 	/* From now on we are sure all drivers support suspend/resume
@@ -1470,6 +1473,15 @@ int usb_resume(struct device *dev, pm_message_t msg)
 	struct usb_device	*udev = to_usb_device(dev);
 	int			status;
 
+	/*
+	 * Some buses would like to keep their devices in suspend
+	 * state after system resume.  Their resume happen when
+	 * a remote wakeup is detected or interface driver start
+	 * I/O.
+	 */
+	if (udev->bus->skip_resume)
+		return 0;
+
 	/* For all calls, take the device back to full power and
 	 * tell the PM core in case it was autosuspended previously.
 	 * Unbind the interfaces that will need rebinding later,

drivers/usb/host/xhci-plat.c

@@ -167,6 +167,8 @@ static int xhci_plat_probe(struct platform_device *pdev)
 	if (!hcd)
 		return -ENOMEM;
 
+	hcd_to_bus(hcd)->skip_resume = true;
+
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	hcd->regs = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(hcd->regs)) {
@@ -221,6 +223,8 @@ static int xhci_plat_probe(struct platform_device *pdev)
 		goto disable_clk;
 	}
 
+	hcd_to_bus(xhci->shared_hcd)->skip_resume = true;
+
 	if ((node && of_property_read_bool(node, "usb3-lpm-capable")) ||
 			(pdata && pdata->usb3_lpm_capable))
 		xhci->quirks |= XHCI_LPM_SUPPORT;

include/linux/usb.h

@@ -395,6 +395,15 @@ struct usb_bus {
 	struct mon_bus *mon_bus;	/* non-null when associated */
 	int monitored;			/* non-zero when monitored */
 #endif
+	unsigned skip_resume:1;		/* All USB devices are brought into full
+					 * power state after system resume. It
+					 * is desirable for some buses to keep
+					 * their devices in suspend state even
+					 * after system resume. The devices
+					 * are resumed later when a remote
+					 * wakeup is detected or an interface
+					 * driver starts I/O.
+					 */
 };
 
 struct usb_dev_state;