usb: gadget: Allow a non-SuperSpeed gadget to support LPM

This commit allows a gadget that does not support SuperSpeed to indicate
that it supports LPM. It does this by setting the 'lpm_capable' flag in
the gadget structure.

If a gadget sets this, the composite gadget framework will set the
bcdUSB to 0x0201 to indicate that this supports BOS descriptors, and
also return a USB 2.0 Extension descriptor as part of the BOS descriptor
set.

See USB 2.0 LPM ECN Section 3.

Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Sevak Arakelyan <sevaka@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/composite.c

@@ -1608,7 +1608,10 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 					cdev->desc.bcdUSB = cpu_to_le16(0x0210);
 				}
 			} else {
-				cdev->desc.bcdUSB = cpu_to_le16(0x0200);
+				if (gadget->lpm_capable)
+					cdev->desc.bcdUSB = cpu_to_le16(0x0201);
+				else
+					cdev->desc.bcdUSB = cpu_to_le16(0x0200);
 			}
 
 			value = min(w_length, (u16) sizeof cdev->desc);
@@ -1639,7 +1642,8 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 				value = min(w_length, (u16) value);
 			break;
 		case USB_DT_BOS:
-			if (gadget_is_superspeed(gadget)) {
+			if (gadget_is_superspeed(gadget) ||
+			    gadget->lpm_capable) {
 				value = bos_desc(cdev);
 				value = min(w_length, (u16) value);
 			}

include/linux/usb/gadget.h

@@ -352,6 +352,8 @@ struct usb_gadget_ops {
  * @deactivated: True if gadget is deactivated - in deactivated state it cannot
  *	be connected.
  * @connected: True if gadget is connected.
+ * @lpm_capable: If the gadget max_speed is FULL or HIGH, this flag
+ *	indicates that it supports LPM as per the LPM ECN & errata.
  *
  * Gadgets have a mostly-portable "gadget driver" implementing device
  * functions, handling all usb configurations and interfaces.  Gadget
@@ -404,6 +406,7 @@ struct usb_gadget {
 	unsigned			is_selfpowered:1;
 	unsigned			deactivated:1;
 	unsigned			connected:1;
+	unsigned			lpm_capable:1;
 };
 #define work_to_gadget(w)	(container_of((w), struct usb_gadget, work))