xHCI/USB: Make xHCI driver have a BOS descriptor.

To add USB 3.0 link power management (LPM), we need to know what the U1
and U2 exit latencies are for the xHCI host controller. External USB 3.0
hubs report these values through the SuperSpeed Capabilities descriptor in
the BOS descriptor. Make the USB 3.0 roothub for the xHCI host behave
like an external hub and return the BOS descriptors.

The U1 and U2 exit latencies will vary across each host controller, so we
need to dynamically fill those values in by reading the exit latencies out
of the xHC registers. Make the roothub code in the USB core handle
hub_control() returning the length of the data copied.

Signed-off-by: Sarah Sharp <[e-mail]>
Acked-by: Alan Stern <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/core/hcd.c

···
 	struct usb_ctrlrequest *cmd;
  	u16		typeReq, wValue, wIndex, wLength;
 	u8		*ubuf = urb->transfer_buffer;
-	u8		tbuf [sizeof (struct usb_hub_descriptor)]
+	/*
+	 * tbuf should be as big as the BOS descriptor and
+	 * the USB hub descriptor.
+	 */
+	u8		tbuf[USB_DT_BOS_SIZE + USB_DT_USB_SS_CAP_SIZE]
 		__attribute__((aligned(4)));
 	const u8	*bufp = tbuf;
 	unsigned	len = 0;
···
 			else /* unsupported IDs --> "protocol stall" */
 				goto error;
 			break;
+		case USB_DT_BOS << 8:
+			goto nongeneric;
 		default:
 			goto error;
 		}
···
 	/* CLASS REQUESTS (and errors) */
 
 	default:
+nongeneric:
 		/* non-generic request */
 		switch (typeReq) {
 		case GetHubStatus:
···
 			break;
 		case GetHubDescriptor:
 			len = sizeof (struct usb_hub_descriptor);
+			break;
+		case DeviceRequest | USB_REQ_GET_DESCRIPTOR:
+			/* len is returned by hub_control */
 			break;
 		}
 		status = hcd->driver->hub_control (hcd,
···
 		status = -EPIPE;
 	}
 
-	if (status) {
+	if (status < 0) {
 		len = 0;
 		if (status != -EPIPE) {
 			dev_dbg (hcd->self.controller,
···
 				typeReq, wValue, wIndex,
 				wLength, status);
 		}
+	} else if (status > 0) {
+		/* hub_control may return the length of data copied. */
+		len = status;
+		status = 0;
 	}
 	if (len) {
 		if (urb->transfer_buffer_length < len)

drivers/usb/host/xhci-hub.c

···
 #define	PORT_RWC_BITS	(PORT_CSC | PORT_PEC | PORT_WRC | PORT_OCC | \
 			 PORT_RC | PORT_PLC | PORT_PE)
 
+/* usb 1.1 root hub device descriptor */
+static u8 usb_bos_descriptor [] = {
+	USB_DT_BOS_SIZE,		/*  __u8 bLength, 5 bytes */
+	USB_DT_BOS,			/*  __u8 bDescriptorType */
+	0x0F, 0x00,			/*  __le16 wTotalLength, 15 bytes */
+	0x1,				/*  __u8 bNumDeviceCaps */
+	/* First device capability */
+	USB_DT_USB_SS_CAP_SIZE,		/*  __u8 bLength, 10 bytes */
+	USB_DT_DEVICE_CAPABILITY,	/* Device Capability */
+	USB_SS_CAP_TYPE,		/* bDevCapabilityType, SUPERSPEED_USB */
+	0x00,				/* bmAttributes, LTM off by default */
+	USB_5GBPS_OPERATION, 0x00,	/* wSpeedsSupported, 5Gbps only */
+	0x03,				/* bFunctionalitySupport,
+					   USB 3.0 speed only */
+	0x00,				/* bU1DevExitLat, set later. */
+	0x00, 0x00			/* __le16 bU2DevExitLat, set later. */
+};
+
+
 static void xhci_common_hub_descriptor(struct xhci_hcd *xhci,
 		struct usb_hub_descriptor *desc, int ports)
 {
···
 		xhci_hub_descriptor(hcd, xhci,
 				(struct usb_hub_descriptor *) buf);
 		break;
+	case DeviceRequest | USB_REQ_GET_DESCRIPTOR:
+		if ((wValue & 0xff00) != (USB_DT_BOS << 8))
+			goto error;
+
+		if (hcd->speed != HCD_USB3)
+			goto error;
+
+		memcpy(buf, &usb_bos_descriptor,
+				USB_DT_BOS_SIZE + USB_DT_USB_SS_CAP_SIZE);
+		temp = xhci_readl(xhci, &xhci->cap_regs->hcs_params3);
+		buf[12] = HCS_U1_LATENCY(temp);
+		put_unaligned_le16(HCS_U2_LATENCY(temp), &buf[13]);
+
+		spin_unlock_irqrestore(&xhci->lock, flags);
+		return USB_DT_BOS_SIZE + USB_DT_USB_SS_CAP_SIZE;
 	case GetPortStatus:
 		if (!wIndex || wIndex > max_ports)
 			goto error;