Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932766AbWKSSWJ (ORCPT ); Sun, 19 Nov 2006 13:22:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932769AbWKSSWJ (ORCPT ); Sun, 19 Nov 2006 13:22:09 -0500 Received: from smtp.osdl.org ([65.172.181.25]:61107 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S932766AbWKSSWH (ORCPT ); Sun, 19 Nov 2006 13:22:07 -0500 Date: Sun, 19 Nov 2006 10:21:52 -0800 (PST) From: Linus Torvalds To: "Rafael J. Wysocki" cc: Chuck Ebbert <76306.1226@compuserve.com>, linux-kernel , Andrew Morton Subject: Re: [patch] PM: suspend/resume debugging should depend on SOFTWARE_SUSPEND In-Reply-To: <200611191844.14354.rjw@sisk.pl> Message-ID: References: <200611190320_MC3-1-D21B-111C@compuserve.com> <200611191844.14354.rjw@sisk.pl> 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: 2814 Lines: 72 On Sun, 19 Nov 2006, Rafael J. Wysocki wrote: > > In fact that's up to 30 seconds on a modern box, usually less than that. Right. If the machine boots quickly, it's fast. Of course, if the machine boots quickly, you might as well often just shut down and reboot. > And suspend-to-ram doesn't work on quilte a lot of boxes right now. Also, you > can use the software suspend on boxes that don't support the suspend-to-ram > at all. One large reason STR often doesn't work is that people don't even test it, because people point to the suspend-to-disk instead. suspend-to-disk is the problem, not the solution. I've been working at making the machines I have able to STR, and almost always it's a driver that is buggy. Thank God for the suspend/resume debugging - the thing that Chuck tried to disable. That's often the _only_ way to debug these things, and it's actually pretty powerful (but time-consuming - having to insert TRACE_RESUME() markers into the device driver that doesn't resume and recompile and reboot). Anyway, the way to debug this for people who are interested (have a machine that doesn't boot) is: - enable PM_DEBUG, and PM_TRACE - use a script like this: #!/bin/sh sync echo 1 > /sys/power/pm_trace echo mem > /sys/power/state to suspend - if it doesn't come back up (which is usually the problem), reboot by holding the power button down, and look at the dmesg output for things like Magic number: 4:156:725 hash matches drivers/base/power/resume.c:28 hash matches device 0000:01:00.0 which means that the last trace event was just before trying to resume device 0000:01:00.0. Then figure out what driver is controlling that device (lspci and /sys/devices/pci* is your friend), and see if you can fix it, disable it, or trace into its resume function. For example, the above happens to be the VGA device on my EVO, which I used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out that "radeonfb" simply cannot resume that device - it tries to set the PLL's, and it just _hangs_. Using the regular VGA console and letting X resume it instead works fine. The point being that PM_TRACE is wonderful, and it's wonderful exactly for NOT using suspend-to-disk. The other point being that people have gotten lazy, and accept half a minute (minimum - usually it's longer) boot times, when STR is a lot more pleasant, but it does require some detective work when it doesn't boot. I wish more people tried STR, instead of having the STD people tell them not to! Linus - 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/