xHCI: keep track of ports being resumed and indicate in hub_status_data

This commit adds a bit-array to xhci bus_state for keeping track of
which ports are undergoing a resume transition. If any of the bits
are set when xhci_hub_status_data() is called, the routine will return
a non-zero value even if no ports have any status changes pending.
This will allow usbcore to handle races between root-hub suspend and
port wakeup.

This patch should be backported to kernels as old as 3.4, that contain
the commit 879d38e6bc36d73b0ac40ec9b0d839fda9fa8b1a "USB: fix race
between root-hub suspend and remote wakeup".

Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: stable@vger.kernel.org

1 files changed, 12 insertions, 10 deletions

diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index 673ad120c43e..89850a82d51b 100644
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -558,6 +558,7 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
 				xhci_dbg(xhci, "Resume USB2 port %d\n",
 					wIndex + 1);
 				bus_state->resume_done[wIndex] = 0;
+				clear_bit(wIndex, &bus_state->resuming_ports);
 				xhci_set_link_state(xhci, port_array, wIndex,
 							XDEV_U0);
 				xhci_dbg(xhci, "set port %d resume\n",
@@ -845,7 +846,12 @@ int xhci_hub_status_data(struct usb_hcd *hcd, char *buf)
 	/* Initial status is no changes */
 	retval = (max_ports + 8) / 8;
 	memset(buf, 0, retval);
-	status = 0;
+
+	/*
+	 * Inform the usbcore about resume-in-progress by returning
+	 * a non-zero value even if there are no status changes.
+	 */
+	status = bus_state->resuming_ports;
 
 	mask = PORT_CSC | PORT_PEC | PORT_OCC | PORT_PLC | PORT_WRC;
 
@@ -885,15 +891,11 @@ int xhci_bus_suspend(struct usb_hcd *hcd)
 	spin_lock_irqsave(&xhci->lock, flags);
 
 	if (hcd->self.root_hub->do_remote_wakeup) {
-		port_index = max_ports;
-		while (port_index--) {
-			if (bus_state->resume_done[port_index] != 0) {
-				spin_unlock_irqrestore(&xhci->lock, flags);
-				xhci_dbg(xhci, "suspend failed because "
-						"port %d is resuming\n",
-						port_index + 1);
-				return -EBUSY;
-			}
+		if (bus_state->resuming_ports) {
+			spin_unlock_irqrestore(&xhci->lock, flags);
+			xhci_dbg(xhci, "suspend failed because "
+						"a port is resuming\n");
+			return -EBUSY;
 		}
 	}