From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754838AbYANJFW (ORCPT ); Mon, 14 Jan 2008 04:05:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753225AbYANJFF (ORCPT ); Mon, 14 Jan 2008 04:05:05 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:38821 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753100AbYANJFA (ORCPT ); Mon, 14 Jan 2008 04:05:00 -0500 Date: Mon, 14 Jan 2008 10:04:59 +0100 From: Pavel Machek To: Russell King Cc: Linux Kernel List , Alan Cox , Andrew Morton Subject: Re: [PATCH: 2/2] [SERIAL] avoid stalling suspend if serial port won't drain Message-ID: <20080114090459.GB4024@elf.ucw.cz> References: <20080108115148.GB10546@flint.arm.linux.org.uk> <20080108115703.GA27179@flint.arm.linux.org.uk> <20080111101721.GA4463@ucw.cz> <20080114002912.GA19195@flint.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080114002912.GA19195@flint.arm.linux.org.uk> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 2008-01-14 00:29:12, Russell King wrote: > On Fri, Jan 11, 2008 at 10:17:21AM +0000, Pavel Machek wrote: > > On Tue 2008-01-08 11:57:03, Russell King wrote: > > > + if (!tries) > > > + printk(KERN_ERR "%s%s%s%d: Unable to drain transmitter\n", > > > + port->dev ? port->dev->bus_id : "", > > > + port->dev ? ": " : "", > > > + drv->dev_name, port->line); > > > > > > ops->shutdown(port); > > > } > > > > > > > Is printk() enough for 'we've just lost your data' condition? Maybe we > > should abort suspend if we can't drain fifo? > > That would mean that a port set for hardware flow control, with hardware > implemented flow control, has CTS deasserted, you'll never suspend. Yep. > If you're suspending because your battery is almost dead what would you > prefer - the system being prevented from suspending and losing complete > power unexpectedly, resulting in complete data loss, or losing the > characters in the serial port and suspending? > > Which is the lesser of two evils? Not sure, but there's third option -- correct but more work. What about saving/restoring fifo state? That will not stall suspend, nor will loose data. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html