1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
index cbc4d491e626..faf039ac6573 100644
--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c
@@ -242,8 +242,28 @@ static int xhci_pci_suspend(struct usb_hcd *hcd, bool do_wakeup)
 static int xhci_pci_resume(struct usb_hcd *hcd, bool hibernated)
 {
         struct xhci_hcd         *xhci = hcd_to_xhci(hcd);
+        struct pci_dev          *pdev = to_pci_dev(hcd->self.controller);
         int                     retval = 0;
 
+        /* The BIOS on systems with the Intel Panther Point chipset may or may
+         * not support xHCI natively.  That means that during system resume, it
+         * may switch the ports back to EHCI so that users can use their
+         * keyboard to select a kernel from GRUB after resume from hibernate.
+         *
+         * The BIOS is supposed to remember whether the OS had xHCI ports
+         * enabled before resume, and switch the ports back to xHCI when the
+         * BIOS/OS semaphore is written, but we all know we can't trust BIOS
+         * writers.
+         *
+         * Unconditionally switch the ports back to xHCI after a system resume.
+         * We can't tell whether the EHCI or xHCI controller will be resumed
+         * first, so we have to do the port switchover in both drivers.  Writing
+         * a '1' to the port switchover registers should have no effect if the
+         * port was already switched over.
+         */
+        if (usb_is_intel_switchable_xhci(pdev))
+                usb_enable_xhci_ports(pdev);
+
         retval = xhci_resume(xhci, hibernated);
         return retval;
 }