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-rw-r--r--drivers/usb/host/uhci-hcd.c14
1 files changed, 7 insertions, 7 deletions
diff --git a/drivers/usb/host/uhci-hcd.c b/drivers/usb/host/uhci-hcd.c
index fdf54295da7..0d5d2545bf0 100644
--- a/drivers/usb/host/uhci-hcd.c
+++ b/drivers/usb/host/uhci-hcd.c
@@ -495,24 +495,24 @@ static int uhci_reset(struct usb_hcd *hcd)
/* The UHCI spec says devices must have 2 ports, and goes on to say
* they may have more but gives no way to determine how many there
- * are. However, according to the UHCI spec, Bit 7 of the port
+ * are. However according to the UHCI spec, Bit 7 of the port
* status and control register is always set to 1. So we try to
- * use this to our advantage.
+ * use this to our advantage. Another common failure mode when
+ * a nonexistent register is addressed is to return all ones, so
+ * we test for that also.
*/
for (port = 0; port < (io_size - USBPORTSC1) / 2; port++) {
unsigned int portstatus;
portstatus = inw(uhci->io_addr + USBPORTSC1 + (port * 2));
- if (!(portstatus & 0x0080))
+ if (!(portstatus & 0x0080) || portstatus == 0xffff)
break;
}
if (debug)
dev_info(uhci_dev(uhci), "detected %d ports\n", port);
- /* Anything less than 2 or greater than 7 is weird,
- * so we'll ignore it.
- */
- if (port < 2 || port > UHCI_RH_MAXCHILD) {
+ /* Anything greater than 7 is weird so we'll ignore it. */
+ if (port > UHCI_RH_MAXCHILD) {
dev_info(uhci_dev(uhci), "port count misdetected? "
"forcing to 2 ports\n");
port = 2;