xhci: Disable MSI for some Fresco Logic hosts.

Some Fresco Logic hosts, including those found in the AUAU N533V laptop,
advertise MSI, but fail to actually generate MSI interrupts.  Add a new
xHCI quirk to skip MSI enabling for the Fresco Logic host controllers.
Fresco Logic confirms that all chips with PCI vendor ID 0x1b73 and device
ID 0x1000, regardless of PCI revision ID, do not support MSI.

This should be backported to stable kernels as far back as 2.6.36, which
was the first kernel to support MSI on xHCI hosts.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Reported-by: Sergey Galanov <sergey.e.galanov@gmail.com>
Cc: stable@kernel.org

drivers/usb/host/xhci-pci.c

@@ -106,12 +106,22 @@ static int xhci_pci_setup(struct usb_hcd *hcd)
 
 	/* Look for vendor-specific quirks */
 	if (pdev->vendor == PCI_VENDOR_ID_FRESCO_LOGIC &&
-			pdev->device == PCI_DEVICE_ID_FRESCO_LOGIC_PDK &&
-			pdev->revision == 0x0) {
+			pdev->device == PCI_DEVICE_ID_FRESCO_LOGIC_PDK) {
+		if (pdev->revision == 0x0) {
 			xhci->quirks |= XHCI_RESET_EP_QUIRK;
 			xhci_dbg(xhci, "QUIRK: Fresco Logic xHC needs configure"
 					" endpoint cmd after reset endpoint\n");
 		}
+		/* Fresco Logic confirms: all revisions of this chip do not
+		 * support MSI, even though some of them claim to in their PCI
+		 * capabilities.
+		 */
+		xhci->quirks |= XHCI_BROKEN_MSI;
+		xhci_dbg(xhci, "QUIRK: Fresco Logic revision %u "
+				"has broken MSI implementation\n",
+				pdev->revision);
+	}
+
 	if (pdev->vendor == PCI_VENDOR_ID_NEC)
 		xhci->quirks |= XHCI_NEC_HOST;
 

drivers/usb/host/xhci.c

@@ -430,12 +430,19 @@ int xhci_run(struct usb_hcd *hcd)
 		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);
 	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);

drivers/usb/host/xhci.h

@@ -1307,6 +1307,7 @@ struct xhci_hcd {
  * commands.
  */
 #define XHCI_EP_LIMIT_QUIRK	(1 << 5)
+#define XHCI_BROKEN_MSI		(1 << 6)
 	unsigned int		num_active_eps;
 	unsigned int		limit_active_eps;
 	/* There are two roothubs to keep track of bus suspend info for */