UHCI: increase Resume-Detect-off delay

The UHCI controller in my laptop takes longer to turn off the
Resume-Detect bit than the 4 us allowed by uhci-hcd.  Presumably other
computers will have the same problem.

This patch (as752) increases the maximum delay to 10 us, which should be
plenty, and uses polling to avoid penalizing systems which can turn the
bit off more quickly.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/uhci-hub.c b/drivers/usb/host/uhci-hub.c
index c545ef92fe29ad130a7b1de0088a945e4bd29751..16fb72eb6fc9213785216414293d7f27dedd8546 100644 (file)
--- a/drivers/usb/host/uhci-hub.c
+++ b/drivers/usb/host/uhci-hub.c
@@ -84,6 +84,7 @@ static void uhci_finish_suspend(struct uhci_hcd *uhci, int port,
                unsigned long port_addr)
 {
        int status;
+       int i;
 
        if (inw(port_addr) & (USBPORTSC_SUSP | USBPORTSC_RD)) {
                CLR_RH_PORTSTAT(USBPORTSC_SUSP | USBPORTSC_RD);
@@ -92,9 +93,14 @@ static void uhci_finish_suspend(struct uhci_hcd *uhci, int port,
 
                /* The controller won't actually turn off the RD bit until
                 * it has had a chance to send a low-speed EOP sequence,
-                * which takes 3 bit times (= 2 microseconds).  We'll delay
-                * slightly longer for good luck. */
-               udelay(4);
+                * which is supposed to take 3 bit times (= 2 microseconds).
+                * Experiments show that some controllers take longer, so
+                * we'll poll for completion. */
+               for (i = 0; i < 10; ++i) {
+                       if (!(inw(port_addr) & USBPORTSC_RD))
+                               break;
+                       udelay(1);
+               }
        }
        clear_bit(port, &uhci->resuming_ports);
 }