lkml.org 
[lkml]   [2013]   [Jul]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] usb: core: don't try to reset_device() a port that got just disconnected
On Tue, Jul 30, 2013 at 07:33:46PM -0700, Julius Werner wrote:
> > Wait a moment. Why does each of these attempts lead to a 5-second
> > timeout? Why don't they fail immediately?
>
> Now that you mention it, that's a very good question. The kernel
> enqueues a control transfer to the now disconnected address because
> it's internal bookkeeping is not yet updated, but I guess that should
> usually fail very fast from an xHC-internal transaction timeout. I
> have now tried to debug the cause of this: I see the transfer being
> enqueued and the doorbell triggered, but never get a transfer event
> back from it (until the software timeout calls usb_kill_urb() which
> stops the endpoint). With the same setup on a PantherPoint system I
> get the same U1/U2 disable control messages on unplugging, but they
> fail within <5ms with a transaction error... so I guess this must be a
> LynxPoint hardware bug.
>
> Regardless, calling usb_reset_device() is still wrong and will at
> least lead to pointless transfer attempts and error messages, so I
> think my patch still has merit.

Hmm, 5 seconds is the xHCI command timeout. Could the driver be
possibly issuing either a Reset Device or Address Device command that
simply times out?

Sarah Sharp


\
 
 \ /
  Last update: 2013-07-31 18:21    [W:0.050 / U:0.880 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site