linux-kernel - Re: Logitech HD Webcam C525 does not work when connected to USB 2 port, works on USB 3

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Date:	Wed, 11 Jul 2012 08:11:14 +0200
From:	Heinz Diehl <htd@...cy-poultry.org>
To:	linux-kernel@...r.kernel.org
Cc:	Frederik Himpe <fhimpe@...enet.be>,
	USB list <linux-usb@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: Logitech HD Webcam C525 does not work when connected to USB 2
 port, works on USB 3

Hi,

I have exactly the same webcam, lsusb says "Bus 002 Device 004: ID
046d:0826 Logitech, Inc."...

On 06.07.2012, Alan Stern wrote: 

> On Thu, 5 Jul 2012, Frederik Himpe wrote:

> > I tried setting to on again, and then this appears in the logs:
> > Jul  5 21:21:59 piranha kernel: [ 9788.223118] usb 1-1.2: USB disconnect, device number 6
> > Jul  5 21:22:00 piranha kernel: [ 9788.330415] usb 1-1.2: new full-speed USB device number 7 using ehci_hcd
> > Jul  5 21:22:00 piranha kernel: [ 9788.402207] usb 1-1.2: device descriptor read/64, error -32
> > Jul  5 21:22:00 piranha kernel: [ 9788.577706] usb 1-1.2: device descriptor read/64, error -32
> > Jul  5 21:22:00 piranha kernel: [ 9788.753203] usb 1-1.2: new full-speed USB device number 8 using ehci_hcd
> > Jul  5 21:22:00 piranha kernel: [ 9788.824996] usb 1-1.2: device descriptor read/64, error -32
> > Jul  5 21:22:00 piranha kernel: [ 9789.000493] usb 1-1.2: device descriptor read/64, error -32
[....]

...and I do not have these messages at all, with or without
autosuspend enabled...
 
> In the long run, it may be necessary to add a quirk entry to always
> use a reset-resume with this device.  You can find similar entries in 
> drivers/usb/core/quirks.c for other Logitech webcams, which makes it 
> seem very likely that one is needed for yours.  If you want you 
> can try adding the appropriate entry and submit it as a patch.

...and it runs fine with or without the quirk, which I added for
testing purposes. 

> None of this explains why there isn't any problem when the webcam is 
> plugged into a USB-3 port, unfortunately.

All this is purely on USB-2, my machine doesn't have any USB-3 port,
with vanilla 3.4.4 kernel. If nobody did, should I submit a patch 
containing the quirk anyway?

If I can help testing, feel free to contact me.



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