1 files changed, 11 insertions, 3 deletions

diff --git a/drivers/usb/host/ehci-hub.c b/drivers/usb/host/ehci-hub.c
index ffc90295a95f..74f62d68f013 100644
--- a/drivers/usb/host/ehci-hub.c
+++ b/drivers/usb/host/ehci-hub.c
@@ -872,15 +872,23 @@ int ehci_hub_control(
 ) {
         struct ehci_hcd *ehci = hcd_to_ehci (hcd);
         int             ports = HCS_N_PORTS (ehci->hcs_params);
-        u32 __iomem     *status_reg = &ehci->regs->port_status[
-                                (wIndex & 0xff) - 1];
-        u32 __iomem     *hostpc_reg = &ehci->regs->hostpc[(wIndex & 0xff) - 1];
+        u32 __iomem     *status_reg, *hostpc_reg;
         u32             temp, temp1, status;
         unsigned long   flags;
         int             retval = 0;
         unsigned        selector;
 
         /*
+         * Avoid underflow while calculating (wIndex & 0xff) - 1.
+         * The compiler might deduce that wIndex can never be 0 and then
+         * optimize away the tests for !wIndex below.
+         */
+        temp = wIndex & 0xff;
+        temp -= (temp > 0);
+        status_reg = &ehci->regs->port_status[temp];
+        hostpc_reg = &ehci->regs->hostpc[temp];
+
+        /*
          * FIXME:  support SetPortFeatures USB_PORT_FEAT_INDICATOR.
          * HCS_INDICATOR may say we can change LEDs to off/amber/green.
          * (track current state ourselves) ... blink for diagnostics,