linux-kernel - Re: EHCI Regression in 2.6.23-rc2

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Date:	Tue, 14 Aug 2007 01:01:19 -0700
From:	David Brownell <david-b@...bell.net>
To:	webmaster@...gonslave.de
Cc:	Stuart_Hayes@...l.com, greg@...ah.com,
	linux-kernel@...r.kernel.org,
	linux-usb-devel@...ts.sourceforge.net, jikos@...os.cz
Subject: Re: EHCI Regression in 2.6.23-rc2

On Monday 13 August 2007, Daniel Exner wrote:
> David Brownell wrote:
> > On Monday 13 August 2007, Stuart_Hayes@...l.com wrote:
> > > With the VIA controller I have,
> >
> > Which kind is that?  The VT6202 is buggy as all get-out, and
> > they sold a *LOT* of those discrete chips for use in add-on PCI
> > cards.  We generally warn people away from those.  A more current
> > version is the VT6212, which was much more usable.  (If it says
> > EHCI 0.95, it's a VT6202... their EHCI 1.0 chips were much better.)
>
> Where exactly should I search for this? Neither lspci nor lsusb showed any 
> hint on the EHCI rev. the chip conforms to..

The driver logs that information as it starts; on this sytem:

 ehci_hcd 0000:00:02.2: USB 2.0 started, EHCI 1.00, driver 10 Dec 2004

vs "EHCI 0.95".

 
> [..]
> > > Perhaps for now the best thing would just be to bypass the EHCI CPU
> > > frequency notifier code (i.e., my patch) for VIA EHCI controllers, since
> > > they are broken.  Would a hard-coded blacklist (just an "if
> > > (manufacturer==VIA)..." type thing) be OK?
> >
> > Yes ... although if you don't need to blacklist their EHCI 1.0 chips
> > don't do it.  (Any VIA EHCI integrated into a southbridge is going
> > to follow spec rev 1.0 pretty well, modulo idiosyncratic timings.)
>  
> I guess its needed to blacklist even the ECHI 1.0 chips, since my problem is
> with exactly one of those ;)

Something doesn't add up then ... above you ask where to find that info,
but here you say you already got it from somwhere ... ?


> I'm not really into USB protocol specs, but perhaps its possible to test 
> wether the problem Stuarts patch addressed can actually happen on VIA EHCI 
> chips? Perhaps those guys solved the problem in Hard/Firmware..

Theoretically possible, and I've certainly seen hardware made to do
stranger things than that.


> > > I've also acquired a card with an NEC EHCI controller on it, which I'm
> > > going to look at while I'm into it...
> >
> > Another case where there are a lot of add-on "EHCI 0.95" cards; but
> > in this case the quirks were less significant.
>
> Some guy donated me a PCMCIA card with one of those, cause it'll wont work in 
> his Windows only Notebook :)

A NEC 0.95 ??  Should be fine with Linux.  Assuming no bugs have
crept in.

- Dave



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