linux-kernel - Re: [BUG] Loading both ehci-hcd and uhci-hcd drivers causes my printer to fail

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Date:	Mon, 09 Mar 2009 14:26:46 +0200
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Greg KH <greg@...ah.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [BUG] Loading both ehci-hcd and uhci-hcd drivers causes my
 printer to fail

On Mon, 2009-03-09 at 12:07 +0200, Maxim Levitsky wrote:
> On Sun, 2009-03-08 at 12:58 -0400, Alan Stern wrote:
> > On Sun, 8 Mar 2009, Maxim Levitsky wrote:
> > 
> > > > No, adding a dependency won't work because it is valid to load 
> > > > uhci-hcd without ehci-hcd.  The only time a problem occurs is if you 
> > > > load both of them in the wrong order.  (And in fact it's pretty rare 
> > > > for that to cause a real problem -- mostly you just get some annoying 
> > > > messages in the log.)
> > > But since it can cause a problem, this has to be somehow automatically
> > > fixed isn't it?
> > 
> > Can it cause a problem?  I'm not so sure -- it depends on what you mean 
> > by "problem".  One person complained forcefully just because he didn't 
> > like all the extra "disconnect" messages in the system log, even though 
> > everything worked perfectly.
> > 
> > > For example how to I ensure the correct order with udev?
> > 
> > You can't.  But you can add rules to /etc/modprobe.conf to insure that 
> > ehci-hcd is always loaded before uhci-hcd.
> > 
> > > > CONFIG_USB_EHCI_ROOT_HUB_TT shouldn't make any difference at all.  
> > > > That setting matters only for hardware using the ARC/TDI design, which
> > > > is not present in your Intel chipset.  Likewise, provided ehci-hcd is
> > > > loaded first, it shouldn't make any difference whether uhci-hcd is
> > > > loaded or not.
> > > Well, I retest this.
> > > But it seems to work
> > 
> > Best would be if you could send two usbmon traces, one showing the 
> > problem and one showing what happens when uhci-hcd isn't loaded but 
> > everything else is the same.  For each test, plug in the printer's USB 
> > cable after starting the trace.
Sorry, sorry, sorry.

is was the CONFIG_USB_EHCI_TT_NEWSCHED that did it.
I confused both options, without the above option printer works
flawlessly.

In addition I instructed modprobe to load ehci when it loads uhci, and
then uhci.

Truth is truth, I have again seen same timeout messages, just after I
reboot the printer. It is possible that some of the hp scripts, eg the
one that loads firmware, queries the printer while firmware loads or so,
anyway even after such message printer works (I printed a page using
it).



Now I will enable again the CONFIG_USB_EHCI_TT_NEWSCHED, and see how
fast it will fail.


Best regards,
	Maxim Levitsky

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