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Subject[patch 22/40] USB: mutual exclusion for EHCI init and port resets


-stable review patch. If anyone has any objections, please let us know.

------------------
From: Alan Stern <stern@rowland.harvard.edu>
patch 32fe01985aa2cb2562f6fc171e526e279abe10db in mainline.

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>
---
drivers/usb/core/hcd.h | 8 +++++++-
drivers/usb/core/hub.c | 15 ++++++++++++++-
drivers/usb/host/ehci-hcd.c | 8 ++++++++
3 files changed, 29 insertions(+), 2 deletions(-)
--- a/drivers/usb/core/hcd.h
+++ b/drivers/usb/core/hcd.h
@@ -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.
*/
@@ -454,5 +456,9 @@ static inline void usbmon_urb_complete(s
: (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__ */
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -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)
{
@@ -1460,6 +1466,11 @@ static int hub_port_reset(struct usb_hub
{
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,
@@ -1490,7 +1501,7 @@ static int hub_port_reset(struct usb_hub
usb_set_device_state(udev, status
? USB_STATE_NOTATTACHED
: USB_STATE_DEFAULT);
- return status;
+ goto done;
}

dev_dbg (hub->intfdev,
@@ -1503,6 +1514,8 @@ static int hub_port_reset(struct usb_hub
"Cannot enable port %i. Maybe the USB cable is bad?\n",
port1);

+ done:
+ up_read(&ehci_cf_port_reset_rwsem);
return status;
}

--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -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.
*/
+ down_write(&ehci_cf_port_reset_rwsem);
hcd->state = HC_STATE_RUNNING;
ehci_writel(ehci, FLAG_CF, &ehci->regs->configured_flag);
ehci_readl(ehci, &ehci->regs->command); /* unblock posted writes */
+ up_write(&ehci_cf_port_reset_rwsem);

temp = HC_VERSION(ehci_readl(ehci, &ehci->caps->hc_capbase));
ehci_info (ehci,
--
-
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