[patch 05/36] USB: fix up EHCI startup synchronization

Greg KH
2007-12-13T06:39:00Z

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

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From: David Brownell <david-b@pacbell.net>

patch 1cb52658b4f5b10a9e91f8e1c21ca2bcc1b9a3ca in mainline.

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: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/usb/host/ehci-hcd.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -571,12 +571,15 @@ 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));

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