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

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Date:	Mon, 9 Mar 2009 12:15:29 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Maxim Levitsky <maximlevitsky@...il.com>
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, 9 Mar 2009, Maxim Levitsky wrote:

> > Is your printer connected directly to the computer, or does it go 
> > through a hub?  (If it is connected directly then EHCI_TT_NEWSCHED 
> > should not affect it at all.)
> > 
> > If it does go through a hub, does it behave better when you attach it 
> > directly?
> > 
> > Alan Stern
> > 
> No, it is connected directly.
> Just tried 'bad' driver, and firmware upload failed
> 
> Do you mean that CONFIG_USB_EHCI_TT_NEWSCHED doesn't affect the driver
> at all when no hub is presented?

That's right.  Transaction Translators (TTs) live inside hubs.  If you 
don't use a hub then the TT code never runs.

> Btw, at least according to lsusb -t, there are no internal hubs in the
> printer.

What does /proc/bus/usb/devices say?

> But it can be a coincidence, it seems that with 'bad' driver printer
> works 'better' to as it failed back few days ago much more often, maybe
> cable is bad, don't know, but according to the web these printers
> 1018/1020.. have usb problems, there is even a readme for that in
> foo2zjz  
> 
> I try to use the 'good' driver 
> (without CONFIG_USB_EHCI_TT_NEWSCHED) for some time.

Please don't forget to collect usbmon traces when the problem occurs.

Alan Stern

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