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 879d38e6 "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

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;
 
@@ -885,17 +891,13 @@ 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) {
+		if (bus_state->resuming_ports) {
 			spin_unlock_irqrestore(&xhci->lock, flags);
 			xhci_dbg(xhci, "suspend failed because "
-						"port %d is resuming\n",
-						port_index + 1);
+						"a port is resuming\n");
 			return -EBUSY;
 		}
 	}
-	}
 
 	port_index = max_ports;
 	bus_state->bus_suspended = 0;

drivers/usb/host/xhci-ring.c

@@ -1377,6 +1377,7 @@ static void handle_port_status(struct xhci_hcd *xhci,
 			xhci_dbg(xhci, "resume HS port %d\n", port_id);
 			bus_state->resume_done[faked_port_index] = jiffies +
 				msecs_to_jiffies(20);
+			set_bit(faked_port_index, &bus_state->resuming_ports);
 			mod_timer(&hcd->rh_timer,
 				  bus_state->resume_done[faked_port_index]);
 			/* Do the rest in GetPortStatus */

drivers/usb/host/xhci.c

@@ -152,7 +152,7 @@ int xhci_reset(struct xhci_hcd *xhci)
 {
 	u32 command;
 	u32 state;
-	int ret;
+	int ret, i;
 
 	state = xhci_readl(xhci, &xhci->op_regs->status);
 	if ((state & STS_HALT) == 0) {
@@ -175,7 +175,15 @@ int xhci_reset(struct xhci_hcd *xhci)
 	 * xHCI cannot write to any doorbells or operational registers other
 	 * than status until the "Controller Not Ready" flag is cleared.
 	 */
-	return handshake(xhci, &xhci->op_regs->status, STS_CNR, 0, 250 * 1000);
+	ret = handshake(xhci, &xhci->op_regs->status, STS_CNR, 0, 250 * 1000);
+
+	for (i = 0; i < 2; ++i) {
+		xhci->bus_state[i].port_c_suspend = 0;
+		xhci->bus_state[i].suspended_ports = 0;
+		xhci->bus_state[i].resuming_ports = 0;
+	}
+
+	return ret;
 }
 
 #ifdef CONFIG_PCI

drivers/usb/host/xhci.h

@@ -1362,6 +1362,8 @@ struct xhci_bus_state {
 	u32			suspended_ports;
 	u32			port_remote_wakeup;
 	unsigned long		resume_done[USB_MAXCHILDREN];
+	/* which ports have started to resume */
+	unsigned long		resuming_ports;
 };
 
 static inline unsigned int hcd_index(struct usb_hcd *hcd)