usb: core: hcd: Add support for deferring roothub registration

commit a44623d upstream.

It has been observed with certain PCIe USB cards (like Inateck connected
to AM64 EVM or J7200 EVM) that as soon as the primary roothub is
registered, port status change is handled even before xHC is running
leading to cold plug USB devices not detected. For such cases, registering
both the root hubs along with the second HCD is required. Add support for
deferring roothub registration in usb_add_hcd(), so that both primary and
secondary roothubs are registered along with the second HCD.

This patch has been added and reverted earier as it triggered a race
in usb device enumeration.
That race is now fixed in 5.16-rc3, and in stable back to 5.4
commit 6cca13d ("usb: hub: Fix locking issues with address0_mutex")
commit 6ae6dc2 ("usb: hub: Fix usb enumeration issue due to address0
race")

CC: stable@vger.kernel.org # 5.4+
Suggested-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Tested-by: Chris Chiu <chris.chiu@canonical.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Link: https://lore.kernel.org/r/20220510091630.16564-2-kishon@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hcd.c

@@ -2816,6 +2816,7 @@ int usb_add_hcd(struct usb_hcd *hcd,
 {
 	int retval;
 	struct usb_device *rhdev;
+	struct usb_hcd *shared_hcd;
 
 	if (!hcd->skip_phy_initialization && usb_hcd_is_primary_hcd(hcd)) {
 		hcd->phy_roothub = usb_phy_roothub_alloc(hcd->self.sysdev);
@@ -2976,13 +2977,26 @@ int usb_add_hcd(struct usb_hcd *hcd,
 		goto err_hcd_driver_start;
 	}
 
+	/* starting here, usbcore will pay attention to the shared HCD roothub */
+	shared_hcd = hcd->shared_hcd;
+	if (!usb_hcd_is_primary_hcd(hcd) && shared_hcd && HCD_DEFER_RH_REGISTER(shared_hcd)) {
+		retval = register_root_hub(shared_hcd);
+		if (retval != 0)
+			goto err_register_root_hub;
+
+		if (shared_hcd->uses_new_polling && HCD_POLL_RH(shared_hcd))
+			usb_hcd_poll_rh_status(shared_hcd);
+	}
+
 	/* starting here, usbcore will pay attention to this root hub */
-	retval = register_root_hub(hcd);
-	if (retval != 0)
-		goto err_register_root_hub;
+	if (!HCD_DEFER_RH_REGISTER(hcd)) {
+		retval = register_root_hub(hcd);
+		if (retval != 0)
+			goto err_register_root_hub;
 
-	if (hcd->uses_new_polling && HCD_POLL_RH(hcd))
-		usb_hcd_poll_rh_status(hcd);
+		if (hcd->uses_new_polling && HCD_POLL_RH(hcd))
+			usb_hcd_poll_rh_status(hcd);
+	}
 
 	return retval;
 
@@ -3020,6 +3034,7 @@ EXPORT_SYMBOL_GPL(usb_add_hcd);
 void usb_remove_hcd(struct usb_hcd *hcd)
 {
 	struct usb_device *rhdev = hcd->self.root_hub;
+	bool rh_registered;
 
 	dev_info(hcd->self.controller, "remove, state %x\n", hcd->state);
 
@@ -3030,6 +3045,7 @@ void usb_remove_hcd(struct usb_hcd *hcd)
 
 	dev_dbg(hcd->self.controller, "roothub graceful disconnect\n");
 	spin_lock_irq (&hcd_root_hub_lock);
+	rh_registered = hcd->rh_registered;
 	hcd->rh_registered = 0;
 	spin_unlock_irq (&hcd_root_hub_lock);
 
@@ -3039,7 +3055,8 @@ void usb_remove_hcd(struct usb_hcd *hcd)
 	cancel_work_sync(&hcd->died_work);
 
 	mutex_lock(&usb_bus_idr_lock);
-	usb_disconnect(&rhdev);		/* Sets rhdev to NULL */
+	if (rh_registered)
+		usb_disconnect(&rhdev);		/* Sets rhdev to NULL */
 	mutex_unlock(&usb_bus_idr_lock);
 
 	/*

include/linux/usb/hcd.h

@@ -124,6 +124,7 @@ struct usb_hcd {
 #define HCD_FLAG_RH_RUNNING		5	/* root hub is running? */
 #define HCD_FLAG_DEAD			6	/* controller has died? */
 #define HCD_FLAG_INTF_AUTHORIZED	7	/* authorize interfaces? */
+#define HCD_FLAG_DEFER_RH_REGISTER	8	/* Defer roothub registration */
 
 	/* The flags can be tested using these macros; they are likely to
 	 * be slightly faster than test_bit().
@@ -134,6 +135,7 @@ struct usb_hcd {
 #define HCD_WAKEUP_PENDING(hcd)	((hcd)->flags & (1U << HCD_FLAG_WAKEUP_PENDING))
 #define HCD_RH_RUNNING(hcd)	((hcd)->flags & (1U << HCD_FLAG_RH_RUNNING))
 #define HCD_DEAD(hcd)		((hcd)->flags & (1U << HCD_FLAG_DEAD))
+#define HCD_DEFER_RH_REGISTER(hcd) ((hcd)->flags & (1U << HCD_FLAG_DEFER_RH_REGISTER))
 
 	/*
 	 * Specifies if interfaces are authorized by default