Patch "usb: xhci: fix config fail of FS hub behind a HS hub with MTT" has been added to the 4.1-stable tree

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 the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
usb-xhci-fix-config-fail-of-fs-hub-behind-a-hs-hub-with-mtt.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

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

From: Chunfeng Yun <[email protected]>

commit 096b110a3dd3c868e4610937c80d2e3f3357c1a9 upstream.

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(+)

@@ -4794,8 +4794,16 @@ int xhci_update_hub_device(struct usb_hc
 	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",

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/usb-xhci-fix-config-fail-of-fs-hub-behind-a-hs-hub-with-mtt.patch