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Commit 1cb52658 authored by David Brownell's avatar David Brownell Committed by Greg Kroah-Hartman
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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: default avatarDavid 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: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 5cf1973a

drivers/usb/host/ehci-hcd.c

+4 −1
Original line number Diff line number Diff line
@@ -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));