[xhci] Forcibly disable SMIs if BIOS fails to release ownership

If the BIOS fails to gracefully release ownership of the xHCI
controller, we can forcibly claim it by disabling all SMIs via the
USB legacy support control/status register.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/usb/xhci.c

  * Claim ownership from BIOS
  *
  * @v xhci		xHCI device
- * @ret rc		Return status code
  */
-static int xhci_legacy_claim ( struct xhci_device *xhci ) {
+static void xhci_legacy_claim ( struct xhci_device *xhci ) {
 	uint32_t ctlsts;
 	uint8_t bios;
 	unsigned int i;
 
 	/* Do nothing unless legacy support capability is present */
 	if ( ! xhci->legacy )
-		return 0;
+		return;
 
 	/* Claim ownership */
 	writeb ( XHCI_USBLEGSUP_OS_OWNED,
 				DBGC ( xhci, "XHCI %p warning: BIOS retained "
 				       "SMIs: %08x\n", xhci, ctlsts );
 			}
-			return 0;
+			return;
 		}
 
 		/* Delay */
 		mdelay ( 1 );
 	}
 
-	DBGC ( xhci, "XHCI %p timed out waiting for BIOS to release "
-	       "ownership\n", xhci );
-	return -ETIMEDOUT;
+	/* BIOS did not release ownership.  Claim it forcibly by
+	 * disabling all SMIs.
+	 */
+	DBGC ( xhci, "XHCI %p could not claim ownership from BIOS: forcibly "
+	       "disabling SMIs\n", xhci );
+	writel ( 0, xhci->cap + xhci->legacy + XHCI_USBLEGSUP_CTLSTS );
 }
 
 /**
 
 	/* Initialise USB legacy support and claim ownership */
 	xhci_legacy_init ( xhci );
-	if ( ( rc = xhci_legacy_claim ( xhci ) ) != 0 )
-		goto err_legacy_claim;
+	xhci_legacy_claim ( xhci );
 
 	/* Fix Intel PCH-specific quirks, if applicable */
 	if ( pci->id->driver_data & XHCI_PCH )
 	if ( pci->id->driver_data & XHCI_PCH )
 		xhci_pch_undo ( xhci, pci );
 	xhci_legacy_release ( xhci );
- err_legacy_claim:
 	iounmap ( xhci->regs );
  err_ioremap:
 	free ( xhci );