linux-kernel - Re: [v4.2-rc1 Regression] usb: Enable LPM for USB 2.01+ full-speed devices

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Date:	Tue, 28 Jun 2016 11:40:13 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Joseph Salisbury <joseph.salisbury@...onical.com>
cc:	Greg KH <gregkh@...uxfoundation.org>, <rtatiya@...eaurora.org>,
	Robert Ancell <robert.ancell@...onical.com>,
	"mathias.nyman@...ux.intel.com" <mathias.nyman@...ux.intel.com>,
	<chasemetzger15@...il.com>, <baolu.lu@...ux.intel.com>,
	<oneukum@...e.com>, <kborer@...il.com>, <jun.li@...escale.com>,
	USB list <linux-usb@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [v4.2-rc1 Regression] usb: Enable LPM for USB 2.01+ full-speed
 devices

On Tue, 28 Jun 2016, Joseph Salisbury wrote:

> On 06/24/2016 08:06 AM, Joseph Salisbury wrote:
> > On 06/22/2016 12:14 PM, Greg KH wrote:
> >> On Wed, Jun 22, 2016 at 11:38:43AM -0400, Joseph Salisbury wrote:
> >>> Hi Rupesh,
> >>>
> >>> A kernel bug report was opened against Ubuntu [0].  After a kernel
> >>> bisect, it was found that reverting the following commit resolved this bug:
> >>>
> >>> commit a8425292816ceaa8c49e29d2114e85d85a73e080
> >>> Author: Rupesh Tatiya <rtatiya@...eaurora.org>
> >>> Date:   Tue Apr 14 16:36:55 2015 +0530
> >>>
> >>>     usb: Enable LPM for USB 2.01+ full-speed devices
> >>>
> >>>
> >>> The regression was introduced as of v4.2-rc1.
> >>>
> >>> I was hoping to get your feedback, since you are the patch author.  Do
> >>> you think gathering any additional data will help diagnose this issue,
> >>> or would it be best to submit a revert request?
> >> Does the problem still happen with 4.7-rc4 or even 4.6?
> >>
> >> 4.2 is pretty old and obsolete you know :)
> >>
> >> thanks,
> >>
> >> greg k-h
> > The regression does exist in 4.6-rc2.  I'll have the latest mainline
> > 4.7-rc4 kernel tested.
> The 4.7-rc4 kernel still exhibits the bug.

Have you tried adding a NO_LPM quirk entry for this device, as I 
suggested in an earlier email?  I can write a patch for this, if you 
want.

Alan Stern