USB: xhci: Set DMA mask for host.

Tell the USB core that we can do DMA directly (instead of needing it to
memory-map the buffers for PIO).  If the xHCI host supports 64-bit addresses,
set the DMA mask accordingly.  Otherwise indicate the host can handle 32-bit DMA
addresses.

This improves performance because the USB core doesn't have to spend time
remapping buffers in high memory into the 32-bit address range.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/xhci-pci.c

@@ -53,6 +53,7 @@ static int xhci_pci_setup(struct usb_hcd *hcd)
 	struct xhci_hcd		*xhci = hcd_to_xhci(hcd);
 	struct pci_dev		*pdev = to_pci_dev(hcd->self.controller);
 	int			retval;
+	u32			temp;
 
 	hcd->self.sg_tablesize = TRBS_PER_SEGMENT - 2;
 
@@ -93,6 +94,14 @@ static int xhci_pci_setup(struct usb_hcd *hcd)
 		return retval;
 	xhci_dbg(xhci, "Reset complete\n");
 
+	temp = xhci_readl(xhci, &xhci->cap_regs->hcc_params);
+	if (HCC_64BIT_ADDR(temp)) {
+		xhci_dbg(xhci, "Enabling 64-bit DMA addresses.\n");
+		dma_set_mask(hcd->self.controller, DMA_BIT_MASK(64));
+	} else {
+		dma_set_mask(hcd->self.controller, DMA_BIT_MASK(32));
+	}
+
 	xhci_dbg(xhci, "Calling HCD init\n");
 	/* Initialize HCD and host controller data structures. */
 	retval = xhci_init(hcd);