Commit 32fe0198 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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USB: mutual exclusion for EHCI init and port resets

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: default avatarAlan Stern <>
Acked-by: default avatarDavid Brownell <>
Cc: David Miller <>
Cc: Dely L Sy <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 17f06022
......@@ -19,6 +19,8 @@
#ifdef __KERNEL__
#include <linux/rwsem.h>
/* This file contains declarations of usbcore internals that are mostly
* used or exposed by Host Controller Drivers.
......@@ -470,5 +472,9 @@ static inline void usbmon_urb_complete(struct usb_bus *bus, struct urb *urb,
: (in_interrupt () ? "in_interrupt" : "can sleep"))
#endif /* __KERNEL__ */
/* This rwsem is for use only by the hub driver and ehci-hcd.
* Nobody else should touch it.
extern struct rw_semaphore ehci_cf_port_reset_rwsem;
#endif /* __KERNEL__ */
......@@ -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.
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.
/* 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
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",
return status;
......@@ -570,10 +570,18 @@ static int ehci_run (struct usb_hcd *hcd)
* are explicitly handed to companion controller(s), so no TT is
* involved with the root hub. (Except where one is integrated,
* and there's no companion controller unless maybe for USB OTG.)
* Turning on the CF flag will transfer ownership of all ports
* from the companions to the EHCI controller. If any of the
* companions are in the middle of a port reset at the time, it
* could cause trouble. Write-locking ehci_cf_port_reset_rwsem
* guarantees that no resets are in progress.
hcd->state = HC_STATE_RUNNING;
ehci_writel(ehci, FLAG_CF, &ehci->regs->configured_flag);
ehci_readl(ehci, &ehci->regs->command); /* unblock posted writes */
temp = HC_VERSION(ehci_readl(ehci, &ehci->caps->hc_capbase));
ehci_info (ehci,
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