patch "usb: xhci: fix config fail of FS hub behind a HS hub with MTT" added to usb-linus

This is a note to let you know that I've just added the patch titled

usb: xhci: fix config fail of FS hub behind a HS hub with MTT

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From: Chunfeng Yun <[email protected]>
Date: Fri, 4 Dec 2015 15:53:43 +0200
Subject: usb: xhci: fix config fail of FS hub behind a HS hub with MTT

if a full speed hub connects to a high speed hub which supports MTT, the MTT field of its slot context will be set to 1 when xHCI driver setups an xHCI virtual device in xhci_setup_addressable_virt_dev(); once usb core fetch its hub descriptor, and need to update the xHC's internal data structures for the device, the HUB field of its slot context will be set to 1 too, meanwhile MTT is also set before, this will cause configure endpoint command fail, so in the case, we should clear MTT to 0 for full speed hub according to section 6.2.2

---
 drivers/usb/host/xhci.c | 8 ++++++++
 1 file changed, 8 insertions(+)

index dfa44d3e8eee..3f912705dcef 100644
@@ -4778,8 +4778,16 @@ int xhci_update_hub_device(struct usb_hcd *hcd, struct usb_device *hdev,
 	ctrl_ctx->add_flags |= cpu_to_le32(SLOT_FLAG);
 	slot_ctx = xhci_get_slot_ctx(xhci, config_cmd->in_ctx);
 	slot_ctx->dev_info |= cpu_to_le32(DEV_HUB);
+	/*
+	 * refer to section 6.2.2: MTT should be 0 for full speed hub,
+	 * but it may be already set to 1 when setup an xHCI virtual
+	 * device, so clear it anyway.
+	 */
 	if (tt->multi)
 		slot_ctx->dev_info |= cpu_to_le32(DEV_MTT);
+	else if (hdev->speed == USB_SPEED_FULL)
+		slot_ctx->dev_info &= cpu_to_le32(~DEV_MTT);
+
 	if (xhci->hci_version > 0x95) {
 		xhci_dbg(xhci, "xHCI version %x needs hub "
 				"TT think time and number of ports\n",

2.6.2