1 files changed, 40 insertions, 1 deletions

diff --git a/drivers/usb/host/ohci-pci.c b/drivers/usb/host/ohci-pci.c
index ca62cb583221..15013f4519ad 100644
--- a/drivers/usb/host/ohci-pci.c
+++ b/drivers/usb/host/ohci-pci.c
@@ -202,6 +202,42 @@ static int __devinit ohci_pci_start (struct usb_hcd *hcd)
         return ret;
 }
 
+#if     defined(CONFIG_USB_PERSIST) && (defined(CONFIG_USB_EHCI_HCD) || \
+                defined(CONFIG_USB_EHCI_HCD_MODULE))
+
+/* Following a power loss, we must prepare to regain control of the ports
+ * we used to own.  This means turning on the port power before ehci-hcd
+ * tries to switch ownership.
+ *
+ * This isn't a 100% perfect solution.  On most systems the OHCI controllers
+ * lie at lower PCI addresses than the EHCI controller, so they will be
+ * discovered (and hence resumed) first.  But there is no guarantee things
+ * will always work this way.  If the EHCI controller is resumed first and
+ * the OHCI ports are unpowered, then the handover will fail.
+ */
+static void prepare_for_handover(struct usb_hcd *hcd)
+{
+        struct ohci_hcd *ohci = hcd_to_ohci(hcd);
+        int             port;
+
+        /* Here we "know" root ports should always stay powered */
+        ohci_dbg(ohci, "powerup ports\n");
+        for (port = 0; port < ohci->num_ports; port++)
+                ohci_writel(ohci, RH_PS_PPS,
+                                &ohci->regs->roothub.portstatus[port]);
+
+        /* Flush those writes */
+        ohci_readl(ohci, &ohci->regs->control);
+        msleep(20);
+}
+
+#else
+
+static inline void prepare_for_handover(struct usb_hcd *hcd)
+{ }
+
+#endif  /* CONFIG_USB_PERSIST etc. */
+
 #ifdef  CONFIG_PM
 
 static int ohci_pci_suspend (struct usb_hcd *hcd, pm_message_t message)
@@ -241,7 +277,10 @@ static int ohci_pci_suspend (struct usb_hcd *hcd, pm_message_t message)
 static int ohci_pci_resume (struct usb_hcd *hcd)
 {
         set_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
-        usb_hcd_resume_root_hub(hcd);
+
+        /* FIXME: we should try to detect loss of VBUS power here */
+        prepare_for_handover(hcd);
+
         return 0;
 }