From: Dan Williams <dan.j.williams@intel.com>
Date: Wed, 21 May 2014 01:09:20 +0000 (-0700)
Subject: usb: synchronize port poweroff and khubd
X-Git-Tag: omap-for-v3.16/fixes-against-rc1~39^2~34^2~21
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=097a155f05e88dc71184ceb93ad1aab1a13d1e41;p=pandora-kernel.git

usb: synchronize port poweroff and khubd

If a port is powered-off, or in the process of being powered-off, prevent
khubd from operating on it.  Otherwise, the following sequence of events
leading to an unintended disconnect may occur:

Events:
(0) <set pm_qos_no_poweroff to '0' for port1>
(1) hub 2-2:1.0: hub_resume
(2) hub 2-2:1.0: port 1: status 0301 change 0000
(3) hub 2-2:1.0: state 7 ports 4 chg 0002 evt 0000
(4) hub 2-2:1.0: port 1, power off status 0000, change 0000, 12 Mb/s
(5) usb 2-2.1: USB disconnect, device number 5

Description:
(1) hub is resumed before sending a ClearPortFeature request
(2) hub_activate() notices the port is connected and sets
    hub->change_bits for the port
(3) hub_events() starts, but at the same time the port suspends
(4) hub_connect_change() sees the disabled port and triggers disconnect

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

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