USB: mutual exclusion for EHCI init and port resets

[pandora-kernel.git] / drivers / usb / host / ehci-hcd.c

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index db00492..c151444 100644 (file)
--- 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,