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authorAlan Stern <stern@rowland.harvard.edu>2007-10-10 16:27:07 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2007-10-12 14:55:34 -0700
commit32fe01985aa2cb2562f6fc171e526e279abe10db (patch)
tree0c1865a1d3e91ae0839147430480c4099b16a06f /drivers/usb/host/ehci-hcd.c
parent17f060224fb9f435c6f9306b7b61419d038def13 (diff)
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: 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>
Diffstat (limited to 'drivers/usb/host/ehci-hcd.c')
-rw-r--r--drivers/usb/host/ehci-hcd.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index db00492588b..c1514442883 100644
--- 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,