linux-kernel - Re: Linux 3.8-rc1 - another regression on USB :-(

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Date:	Sat, 12 Jan 2013 17:54:50 +0100
From:	Oliver Neukum <oliver@...kum.org>
To:	Andreas Mohr <andi@...as.de>
Cc:	Woody Suwalski <terraluna977@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	USB list <linux-usb@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 3.8-rc1 - another regression on USB :-(

On Saturday 12 January 2013 14:16:02 Andreas Mohr wrote:
> > Greg, Linus,
> > It sounds insane, but after banging on the issue I have found out that 
> > USB problem is caused (also in vanilla kernel) with a config change:
> > USB-all built as modules - bad USB
> > USB core built in, UHCI/EHCI modules -  semi functional - but 1Mb/s
> > transfer
> > USB core and UHCI EHCI built-in - bingo - no issues.
> > 
> > Could anybody duplicate that, or is it somehow my setup???
> 
> Since there was no additional reply here (needed) so far,
> some of my (questionably relevant?) thoughts on this:
> 
> There's of course the EHCI vs. UHCI(/OHCI) duality
> (EHCI host controller responsible for high speed transfers,
> the other for 1.1 full speed, both serving the same port connectors).
> So if the coordination between the two is a problem,
> you might end up with merely full speed on a 2.0 port.
> 
> And with drivers builtin vs. module, the init sequence/timing
> might possibly be affected - right?

You should try EHCI first. This has always been true, but the likeliehood
of seeing trouble is variable. This is testable.

EHCI static, UHCI modular - should work
EHCI modular, UHCI static - should fail

	Regards
		Oliver

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