USB: fix up EHCI startup synchronization

A recent patch added software synchronization during EHCI startup,
so ports aren't switched away from the companion controllers after
resets have started.  This patch adds a short delay letting hardware
finish that port switching before any new resets begin ... so both
ends of that hardware race window are closed.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Dave Miller <davem@davemloft.net>
Cc: Dely Sy <dely.l.sy@intel.com>
Cc: stable <stable@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index c1514442883e..5f2d74ed5ad7 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -575,12 +575,15 @@ static int ehci_run (struct usb_hcd *hcd)
          * 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.
+         * guarantees that no resets are in progress.  After we set CF,
+         * a short delay lets the hardware catch up; new resets shouldn't
+         * be started before the port switching actions could complete.
          */
         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 */
+        msleep(5);
         up_write(&ehci_cf_port_reset_rwsem);
 
         temp = HC_VERSION(ehci_readl(ehci, &ehci->caps->hc_capbase));