LKML Archive on
help / color / mirror / Atom feed
From: Jim Lin <>
To: <>, <>,
	<>, <>,
	<>, <>,
	<>, <>,
Cc: <>, <>,
	Jim Lin <>
Subject: [PATCH v11 0/2] usb: xhci: Add Clear_TT_Buffer
Date: Wed, 29 May 2019 22:55:47 +0800	[thread overview]
Message-ID: <> (raw)

USB 2.0 specification chapter 11.17.5 says "as part of endpoint halt
processing for full-/low-speed endpoints connected via a TT, the host
software must use the Clear_TT_Buffer request to the TT to ensure
that the buffer is not in the busy state".

In our case, a full-speed speaker (ConferenceCam) is behind a high-
speed hub (ConferenceCam Connect), sometimes once we get STALL on a
request we may continue to get STALL with the folllowing requests,
like Set_Interface.

Solution is to invoke usb_hub_clear_tt_buffer() to send
Clear_TT_Buffer request to the hub of the device for the following
Set_Interface requests to the device to get ACK successfully.

The Clear_TT_Buffer request sent to the hub includes the address of
the LS/FS child device in wValue field. usb_hub_clear_tt_buffer()
uses udev->devnum to set the address wValue. This won't work for
devices connected to xHC.

For other host controllers udev->devnum is the same as the address of
the usb device, chosen and set by usb core. With xHC the controller
hardware assigns the address, and won't be the same as devnum.

Here we have two patches.
One is to add devaddr in struct usb_device for
usb_hub_clear_tt_buffer() to use.
Another is to invoke usb_hub_clear_tt_buffer() for halt processing.
Signed-off-by: Jim Lin <>

Jim Lin (2):
  usb: Add devaddr in struct usb_device
  usb: xhci: Add Clear_TT_Buffer

 drivers/usb/core/hub.c       |  4 +++-
 drivers/usb/host/xhci-ring.c | 27 ++++++++++++++++++++++++++-
 drivers/usb/host/xhci.c      | 23 +++++++++++++++++++++++
 drivers/usb/host/xhci.h      |  5 +++++
 include/linux/usb.h          |  2 ++
 5 files changed, 59 insertions(+), 2 deletions(-)


             reply	other threads:[~2019-05-29 14:55 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-29 14:55 Jim Lin [this message]
2019-05-29 14:55 ` [PATCH v11 1/2] usb: Add devaddr in struct usb_device Jim Lin
2019-05-29 14:55 ` [PATCH v11 2/2] usb: xhci: Add Clear_TT_Buffer Jim Lin
2019-06-03 10:53 [PATCH v11 0/2] " Jim Lin
2019-06-03 12:23 ` Greg KH
2019-06-04  8:53   ` Jim Lin
2019-06-04  8:59     ` Greg KH
2019-06-04 14:22     ` Alan Stern

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \ \
    --subject='Re: [PATCH v11 0/2] usb: xhci: Add Clear_TT_Buffer' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).