xhci: Show host status when watchdog triggers and host is assumed dead.

Additional debugging to show xHC USBSTS register when stop endpoint
command watchdog triggers and host is assumed dead.

useful to know the current status before the controller is stopped by
the xhci driver and everything is released and freed.
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20200312144517.1593-4-mathias.nyman@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-ring.c

@@ -955,6 +955,7 @@ void xhci_stop_endpoint_command_watchdog(struct timer_list *t)
 	struct xhci_virt_ep *ep = from_timer(ep, t, stop_cmd_timer);
 	struct xhci_hcd *xhci = ep->xhci;
 	unsigned long flags;
+	u32 usbsts;
 
 	spin_lock_irqsave(&xhci->lock, flags);
 
@@ -965,8 +966,11 @@ void xhci_stop_endpoint_command_watchdog(struct timer_list *t)
 		xhci_dbg(xhci, "Stop EP timer raced with cmd completion, exit");
 		return;
 	}
+	usbsts = readl(&xhci->op_regs->status);
 
 	xhci_warn(xhci, "xHCI host not responding to stop endpoint command.\n");
+	xhci_warn(xhci, "USBSTS:%s\n", xhci_decode_usbsts(usbsts));
+
 	ep->ep_state &= ~EP_STOP_CMD_PENDING;
 
 	xhci_halt(xhci);

drivers/usb/host/xhci.h

@@ -2589,6 +2589,35 @@ static inline const char *xhci_decode_portsc(u32 portsc)
 	return str;
 }
 
+static inline const char *xhci_decode_usbsts(u32 usbsts)
+{
+	static char str[256];
+	int ret = 0;
+
+	if (usbsts == ~(u32)0)
+		return " 0xffffffff";
+	if (usbsts & STS_HALT)
+		ret += sprintf(str + ret, " HCHalted");
+	if (usbsts & STS_FATAL)
+		ret += sprintf(str + ret, " HSE");
+	if (usbsts & STS_EINT)
+		ret += sprintf(str + ret, " EINT");
+	if (usbsts & STS_PORT)
+		ret += sprintf(str + ret, " PCD");
+	if (usbsts & STS_SAVE)
+		ret += sprintf(str + ret, " SSS");
+	if (usbsts & STS_RESTORE)
+		ret += sprintf(str + ret, " RSS");
+	if (usbsts & STS_SRE)
+		ret += sprintf(str + ret, " SRE");
+	if (usbsts & STS_CNR)
+		ret += sprintf(str + ret, " CNR");
+	if (usbsts & STS_HCE)
+		ret += sprintf(str + ret, " HCE");
+
+	return str;
+}
+
 static inline const char *xhci_decode_doorbell(u32 slot, u32 doorbell)
 {
 	static char str[256];