[U-Boot] [PATCH] usb: composite: Fix max packet size for USB3.0

[Siva Durga Prasad Paladugu]

For USB3.0, the max packetsize for GET_DESCRIPTOR should be
sent as exponent value for 2. This means for 512, max packet
size should be filled with 9(2^9=512). Also, fill the USB
version field with 3.0 if speed is negotiated to Superspeed.
This fixes the issue of DFU gadget download failure with
superspeed. Without this patch, the max packet size is
overflowed to zero as the bMaxPacketsize is of u8 and hence
host is not able to detect this device.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu at xilinx.com>
Reviewed-by: Bin Meng <bmeng.cn at gmail.com>
---
Changes from RFC:
- Fixed typo in description as per comment.
---
 drivers/usb/gadget/composite.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index 5106cc5..c7e7623 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -735,8 +735,21 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 		case USB_DT_DEVICE:
 			cdev->desc.bNumConfigurations =
 				count_configs(cdev, USB_DT_DEVICE);
-			cdev->desc.bMaxPacketSize0 =
-				cdev->gadget->ep0->maxpacket;
+
+			/*
+			 * If the speed is Super speed, then the supported
+			 * max packet size is 512 and it should be sent as
+			 * exponent of 2. So, 9(2^9=512) should be filled in
+			 * bMaxPacketSize0. Also fill USB version as 3.0
+			 * if speed is Super speed.
+			 */
+			if (cdev->gadget->speed == USB_SPEED_SUPER) {
+				cdev->desc.bMaxPacketSize0 = 9;
+				cdev->desc.bcdUSB = cpu_to_le16(0x0300);
+			} else {
+				cdev->desc.bMaxPacketSize0 =
+					cdev->gadget->ep0->maxpacket;
+			}
 			value = min(w_length, (u16) sizeof cdev->desc);
 			memcpy(req->buf, &cdev->desc, value);
 			break;
-- 
2.7.4