1 files changed, 39 insertions, 0 deletions

diff --git a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c
index 660b80a75cac..1102ce65a3a9 100644
--- a/drivers/usb/host/ehci-pci.c
+++ b/drivers/usb/host/ehci-pci.c
@@ -348,11 +348,50 @@ static int ehci_pci_suspend(struct usb_hcd *hcd, bool do_wakeup)
         return rc;
 }
 
+static bool usb_is_intel_switchable_ehci(struct pci_dev *pdev)
+{
+        return pdev->class == PCI_CLASS_SERIAL_USB_EHCI &&
+                pdev->vendor == PCI_VENDOR_ID_INTEL &&
+                pdev->device == 0x1E26;
+}
+
+static void ehci_enable_xhci_companion(void)
+{
+        struct pci_dev          *companion = NULL;
+
+        /* The xHCI and EHCI controllers are not on the same PCI slot */
+        for_each_pci_dev(companion) {
+                if (!usb_is_intel_switchable_xhci(companion))
+                        continue;
+                usb_enable_xhci_ports(companion);
+                return;
+        }
+}
+
 static int ehci_pci_resume(struct usb_hcd *hcd, bool hibernated)
 {
         struct ehci_hcd         *ehci = hcd_to_ehci(hcd);
         struct pci_dev          *pdev = to_pci_dev(hcd->self.controller);
 
+        /* 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_ehci(pdev))
+                ehci_enable_xhci_companion();
+
         // maybe restore FLADJ
 
         if (time_before(jiffies, ehci->next_statechange))