Re: OHCI root_port_reset() deadly loop...
|[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]|
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 ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Linux-usb-users@xxxxxxxxxxxxxxxxxxxxx To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
[Linux USB] [Linux USB Devel] [Video for Linux] [Linux Audio Users] [Photo] [Yosemite News] [Yosemite Photos] [Video Projectors] [PDAs] [Free Online Dating] [Hacking TiVo] [Linux Kernel] [Linux SCSI] [XFree86] [Devices] [Big List of Linux Books] [16.7MP]