Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753210AbaFHBKC (ORCPT ); Sat, 7 Jun 2014 21:10:02 -0400 Received: from netrider.rowland.org ([192.131.102.5]:48929 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753142AbaFHBKA (ORCPT ); Sat, 7 Jun 2014 21:10:00 -0400 Date: Sat, 7 Jun 2014 21:09:59 -0400 (EDT) From: Alan Stern X-X-Sender: stern@netrider.rowland.org To: Benjamin Herrenschmidt cc: Thadeu Lima de Souza Cascardo , linux-usb , Kernel development list , Greg KH , Sarah Sharp , Mathias Nyman Subject: Re: Missing USB XHCI and EHCI reset for kexec In-Reply-To: <1402180544.3979.3.camel@pasglop> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 8 Jun 2014, Benjamin Herrenschmidt wrote: > Looking at the code a bit more ... that xhci_shutdown() worries me. > > It basically just whacks xhci_halt() and optionally reset() but nothing > is done that I can see to ensure that we aren't concurrently > doing things like queuing URBs, polling the root hub etc... > > That's definitely not clean and while it might work (most of the time > at least) on actual shutdown it's definitely not right for kexec I > reckon. Yes, it really was meant for actual system shutdown. > Now there's a separate discussion that we had a while ago and might > want to resume which is to say that kexec shouldn't be calling > shutdown() anyway, but instead remove() on all drivers which is > a much better code path for the purpose of leaving the device in > a state where a driver can reconnect to it. > > However, in the case of XHCI that leads to another issue described > here: > > http://marc.info/?l=linux-usb&m=139483181809062&w=2 > > For which there was little / no discussion at all... I suppose we could > do a quirk but I don't think the problem is fundamentally > specific to the TI chip, we should probably stop both root hubs > before we halt both HCDs. The issue described in that email seems valid to me. Maybe the patch should be resubmitted. Now that xhci-hcd has changed maintainership, the discussion might move forward. In any case, you certainly can try testing with that patch installed. After all, xhci-hcd should work properly after a rmmod/modprobe sequence, and this is pretty much the same thing. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/