On Tue, 17 Jul 2012, Daniel Drake wrote:
> Hi Alan,
>
> I've been investigating a problem with UVC webcams on the XO-1 laptop
> (CS5536 EHCI).
>
> Running webcam apps, especially guvcview, was killing the entire USB
> bus more often than not ("failed EHCI handshake, HC died, giving up"
> or similar). Reproduced on 3.5-rc7 and throughout various old kernel
> versions too.
>
> I see you've been investigating similar issues and posted 25 EHCI
> patches to usb-next. I pulled that in on top of 3.5-rc7 and it now
> seems to be working reliably. Thanks!
You're welcome. Apparently a lot of people were running across that
same failure mode.
> It is not perfect: we have an internal USB wifi device on the same
> bus, and starting the webcam sometimes (not always) causes the
> wireless module to die. However, this module has always been a bit
> unreliable so we have an automatic reset routine implemented as a
> result. So it resets and comes right back, and then both camera and
> wifi seem to work fine.
>
> Maybe at some point we can debug that small issue and see if something
> can be done. For now though, your patches are a major improvement -
> thanks for rescuing these USB microscopes on the XO-1!
And thanks for testing.
Alan Stern
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