On Tue, Oct 09, 2007 at 12:01:54PM -0400, Alan Stern wrote:
> On Mon, 8 Oct 2007, David Miller wrote:
>
> > As coicidence would have it I finally found a recipe for triggering
> > the issue, and it ties into what you're talking about here.
> >
> > It happens only if I make sure OHCI gets loaded first and then EHCI
> > right afterwards.
> >
> > It seems that indeed it is important for EHCI to get loaded first,
> > and in-kernel this is ensured by the link ordering.
> >
> > However, when both OHCI and EHCI are built as modules (or, similarly
> > I guess, OHCI is built-in and EHCI is modular) there appears to be
> > nothing in userspace which makes sure EHCI gets loaded first.
> >
> > When this triggers, in OHCI's root_port_reset(), the port status
> > register reads 0x111 in that inner-loop and the value never changes.
> > It stays like this forever.
>
> I agree with Ben; the best way to solve this is in the kernel. Even if
> you did manage to make sure that modules were loaded in the right order
> initially, that wouldn't help if somebody starts unloading and loading
> modules by hand.
>
> The underlying cause of the problem appears to be related to the fact
> that it is impossible in principle to detect a disconnect while a
> full/low-speed reset is in progress. However the hardware shouldn't
> rely on this, and it should fail gracefully when an unexpected
> disconnect does occur.
>
> For example, what would the controller do if the user unplugged the USB
> cable right in the middle of a reset?
>
> Anyway, it certainly would be easy enough to make port resets mutually
> exclusive with EHCI initialization. That would work on any platform,
> PCI or not.
That's a good idea, any thoughts as to how to do this? I think I can
find some Intel and Dell people who would be glad to test this out if
you have a proposed patch.
thanks,
greg k-h
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
