usb/xhci: group MSI interrupt registration into its own function

This patch moves the complete MSI/MSI-X/Legacy dance into its own
function. There is however one difference: If the XHCI_BROKEN_MSI flag
is set then we don't free and register the irq, we simply return.
This is preparation for later PCI decouple.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/xhci.c

@@ -397,6 +397,45 @@ static int xhci_run_finished(struct xhci_hcd *xhci)
 	return 0;
 }
 
+static int xhci_try_enable_msi(struct usb_hcd *hcd)
+{
+	struct xhci_hcd *xhci = hcd_to_xhci(hcd);
+	struct pci_dev  *pdev = to_pci_dev(xhci_to_hcd(xhci)->self.controller);
+	int ret;
+
+	/*
+	 * Some Fresco Logic host controllers advertise MSI, but fail to
+	 * generate interrupts.  Don't even try to enable MSI.
+	 */
+	if (xhci->quirks & XHCI_BROKEN_MSI)
+		return 0;
+
+	/* unregister the legacy interrupt */
+	if (hcd->irq)
+		free_irq(hcd->irq, hcd);
+	hcd->irq = -1;
+
+	ret = xhci_setup_msix(xhci);
+	if (ret)
+		/* fall back to msi*/
+		ret = xhci_setup_msi(xhci);
+
+	if (!ret)
+		/* hcd->irq is -1, we have MSI */
+		return 0;
+
+	/* fall back to legacy interrupt*/
+	ret = request_irq(pdev->irq, &usb_hcd_irq, IRQF_SHARED,
+			hcd->irq_descr, hcd);
+	if (ret) {
+		xhci_err(xhci, "request interrupt %d failed\n",
+				pdev->irq);
+		return ret;
+	}
+	hcd->irq = pdev->irq;
+	return 0;
+}
+
 /*
  * Start the HC after it was halted.
  *
@@ -413,9 +452,8 @@ int xhci_run(struct usb_hcd *hcd)
 {
 	u32 temp;
 	u64 temp_64;
-	u32 ret;
+	int ret;
 	struct xhci_hcd *xhci = hcd_to_xhci(hcd);
-	struct pci_dev  *pdev = to_pci_dev(xhci_to_hcd(xhci)->self.controller);
 
 	/* Start the xHCI host controller running only after the USB 2.0 roothub
 	 * is setup.
@@ -426,34 +464,10 @@ int xhci_run(struct usb_hcd *hcd)
 		return xhci_run_finished(xhci);
 
 	xhci_dbg(xhci, "xhci_run\n");
-	/* unregister the legacy interrupt */
-	if (hcd->irq)
-		free_irq(hcd->irq, hcd);
-	hcd->irq = -1;
 
-	/* Some Fresco Logic host controllers advertise MSI, but fail to
-	 * generate interrupts.  Don't even try to enable MSI.
-	 */
-	if (xhci->quirks & XHCI_BROKEN_MSI)
-		goto legacy_irq;
-
-	ret = xhci_setup_msix(xhci);
+	ret = xhci_try_enable_msi(hcd);
 	if (ret)
-		/* fall back to msi*/
-		ret = xhci_setup_msi(xhci);
-
-	if (ret) {
-legacy_irq:
-		/* fall back to legacy interrupt*/
-		ret = request_irq(pdev->irq, &usb_hcd_irq, IRQF_SHARED,
-					hcd->irq_descr, hcd);
-		if (ret) {
-			xhci_err(xhci, "request interrupt %d failed\n",
-					pdev->irq);
-			return ret;
-		}
-		hcd->irq = pdev->irq;
-	}
+		return ret;
 
 #ifdef CONFIG_USB_XHCI_HCD_DEBUGGING
 	init_timer(&xhci->event_ring_timer);