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USB: mutual exclusion for EHCI init and port resets

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This patch (as999) fixes a problem that sometimes shows up when host
controller driver modules are loaded in the wrong order.  If ehci-hcd
happens to initialize an EHCI controller while the companion OHCI or
UHCI controller is in the middle of a port reset, the reset can fail
and the companion may get very confused.  The patch adds an
rw-semaphore and uses it to keep EHCI initialization and port resets
mutually exclusive.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: David Brownell <david-b@pacbell.net>
Cc: David Miller <davem@davemloft.net>
Cc: Dely L Sy <dely.l.sy@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern
2007-10-10 16:27:07 -04:00
committed by Greg Kroah-Hartman
parent 17f060224f
commit 32fe01985a
3 changed files with 29 additions and 2 deletions
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15
drivers/usb/core/hub.c
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@@ -125,6 +125,12 @@ MODULE_PARM_DESC(use_both_schemes,
"try the other device initialization scheme if the "
"first one fails");
/* Mutual exclusion for EHCI CF initialization. This interferes with
* port reset on some companion controllers.
*/
DECLARE_RWSEM(ehci_cf_port_reset_rwsem);
EXPORT_SYMBOL_GPL(ehci_cf_port_reset_rwsem);
static inline char *portspeed(int portstatus)
{
@@ -1581,6 +1587,11 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
{
int i, status;
/* Block EHCI CF initialization during the port reset.
* Some companion controllers don't like it when they mix.
*/
down_read(&ehci_cf_port_reset_rwsem);
/* Reset the port */
for (i = 0; i < PORT_RESET_TRIES; i++) {
status = set_port_feature(hub->hdev,
@@ -1612,7 +1623,7 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
usb_set_device_state(udev, status
? USB_STATE_NOTATTACHED
: USB_STATE_DEFAULT);
return status;
goto done;
}
dev_dbg (hub->intfdev,
@@ -1625,6 +1636,8 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
"Cannot enable port %i. Maybe the USB cable is bad?\n",
port1);
done:
up_read(&ehci_cf_port_reset_rwsem);
return status;
}