Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752089AbXKSTFE (ORCPT ); Mon, 19 Nov 2007 14:05:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752193AbXKSTEx (ORCPT ); Mon, 19 Nov 2007 14:04:53 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:57770 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751853AbXKSTEw (ORCPT ); Mon, 19 Nov 2007 14:04:52 -0500 Date: Mon, 19 Nov 2007 14:04:50 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: David Brownell cc: stable@kernel.org, USB development list , Kernel development list , , , , , , , , , , , , , , , , Andrew Morton Subject: Re: [patch 19/26] USB: mutual exclusion for EHCI init and port resets In-Reply-To: <20071119184128.E43D423C403@adsl-69-226-248-13.dsl.pltn13.pacbell.net> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2008 Lines: 47 On Mon, 19 Nov 2007, David Brownell wrote: > Still needs the following update, IMO ... > > ====== CUT HERE > A recent patch added software synchronization during EHCI startup, > so ports aren't switched away from the companion controllers after > resets have started. This patch adds a short delay letting hardware > get a chance to finish that port switching before any new resets begin. > > That is, both sides of that hardware race window need to be closed. > > Signed-off-by: David Brownell > --- > drivers/usb/host/ehci-hcd.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > --- g26.orig/drivers/usb/host/ehci-hcd.c 2007-11-13 16:07:12.000000000 -0800 > +++ g26/drivers/usb/host/ehci-hcd.c 2007-11-13 16:13:01.000000000 -0800 > @@ -594,12 +594,15 @@ static int ehci_run (struct usb_hcd *hcd > * from the companions to the EHCI controller. If any of the > * companions are in the middle of a port reset at the time, it > * could cause trouble. Write-locking ehci_cf_port_reset_rwsem > - * guarantees that no resets are in progress. > + * guarantees that no resets are in progress. After we set CF, > + * a short delay lets the hardware catch up; new resets shouldn't > + * start before the port switching actions complete. > */ > down_write(&ehci_cf_port_reset_rwsem); > hcd->state = HC_STATE_RUNNING; > ehci_writel(ehci, FLAG_CF, &ehci->regs->configured_flag); > ehci_readl(ehci, &ehci->regs->command); /* unblock posted writes */ > + msleep(5); > up_write(&ehci_cf_port_reset_rwsem); > > temp = HC_VERSION(ehci_readl(ehci, &ehci->caps->hc_capbase)); This addition certainly won't hurt. Did we ever get any feedback as to whether it actually helped? 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/