Some linux notes

Linux suspend-to-RAM on a Dell D830 with NVIDIA graphics

After a recent system update, my laptop's power management went to hell: I could no longer suspend the machine to RAM at all. As I'm always schlepping my laptop everywhere I go, I constantly use suspend-to-RAM and need it to work reliably. A few years ago I ruined a laptop because its suspend feature chose to fail as I was putting it in my bag for a cross-country flight. After the painful experience of cooking one laptop, I really want power management to work!

Power management software interacts with the BIOS, the video driver, the operating system, and (if you're running X) the window manager. This complicated mess works in Windows because hardware vendors work hard to make sure their hardware is Windows-compliant, and they share proprietary specs with Microsoft. With our small market share Linux is an afterthought, leaving us to muddle through on our own. Because of all the different factors, getting it working takes trial and error augmented by educated guessing and plain luck. These notes are the result of several days' experimentation with several different Linux kernels, BIOS versions, and video drivers.

System configuration

The first step is to get low-level suspend-to-RAM working reliably. In experimenting with options to s2ram (see below) you will probably hit on a combination that works. Unfortunately, those same options may fail the next time! Lesson #1: when you see s2ram working once, you're not done. Don't be satisfied until you can invoke s2ram over and over again without it failing. Remember: the worst case is when s2ram works most of the time then fails when it's really needed, like on a cross-country flight. To get reliable results, I needed to experiment with combinations of the BIOS version, the kernel version, and the video driver.

BIOS -- I have been unable to make S2R work with any version of the BIOS other than D830-A02. Dell strongly recommends updating to D830-A04, but after doing so, S2R fails sporadically. Upon upgrading to the most recent version (as of 29 May, 2008), D830-A12, S2R fails pretty much all the time.

If you need to change your BIOS, go to Dell's support page to download a program to flash the BIOS. To run the flash program, you'll need a bootable MS-DOS floppy disk (no kidding!). If you're running a laptop recent enough to be running a 2.6.x kernel you probably don't have a floppy drive, so you'll need to burn a disk image to CD. Google will point you to many pages telling you how to make a DOS boot disk from Linux.
Kernel -- version 2.6.22.17-0.1 works, as does 2.6.22.5-31.
Video driver -- I was able to make S2R work using version 100.14.19 of the NVIDIA driver.

This combination is almost certainly not the only working solution, but it is a place to start. In experimenting or when deciding to upgrade, keep in mind that the behavior seems to depend on the BIOS version most critically, NVIDIA driver next, and kernel last. Be very conservative about updating your BIOS firmware: your vendor probably never tests the BIOS software on Linux at all, so all bets are off.

Having found a combination of BIOS, video driver, and kernel that works, the next step is to set your system files so everything's ready to go each time you start your system.

Bootloader configuration

At boot time, you should turn off framebuffer graphics and also the default AGP module. Do this by passing

vga=0x0 agp=off

as arguments to the boot command line. If you are running the GRUB bootloader, you can have this done automatically by editing the appropriate line in

/boot/grub/menu.lst

Module configuration

Turn off all AGP modules. Run

lsmod | grep agp

to find all module names, and then blacklist them (except agpgart). For example, if you find intel_agp running, add

blacklist intel_agp

to /etc/modprobe.conf.local

NVIDIA driver configuration

After installing the correct NVIDIA driver and setting up xorg.conf correctly, add

Option "NvAGP" "1"

to the Device section of xorg.conf

s2ram configuration

The mid-level command to invoke suspend-to-RAM is s2ram. Allegedly this works out-of-the box for many systems, but the Dell D830 with NVIDIA drivers isn't among them. Advice on dealing with an unknown machine suggests combinations of command-line options to try. I found that

s2ram -f -a 1 -m

works on my combination of BIOS and video driver. Having found command-line options that work, in the file

/etc/pm/config.d/config

set the variable

S2RAM_OPTS="-f -a 1 -m"

so they'll be used automatically upon invoking s2ram.

Permission configuration

At this point, you should be able to do suspend/resume reliably as root. Alas, another nasty surprise may await: you may be forbidden to suspend as an ordinary user. To see if this is likely to be an issue, click on the power icon to bring up the kpowersave menu. See if the Suspend-to-RAM selection is enabled. If so, you're good to go. If Suspend-to-RAM is greyed out, you'll need to change the PolicyKit permissions. On OpenSuSE 10.3, put


<match action="hal-power-*">
<match user="1000">
<return result="yes"/>
</match>
</match>

inside the <config>...</config> block in /etc/PolicyKit/PolicyKit.conf. Apparently the file formats for PolicyKit configuration are in flux, so if you have a different Linux distribution the format is likely to be different. However you do it, you need to add your UID to the list of users allowed to access power management functions.

Configuring suspension upon closing lid

If you run KDE, you can configure kpowersave to suspend-to-RAM upon closing the lid of your laptop. Click on the kpowersave icon (which will be a battery or a power cord) and select Configure KPowerSave. Go to the General Settings tab, then select Event Buttons. For the lid-closing event, select Suspend-to-RAM. Close your lid, and see whether it works. Try it a few times just to be sure.

You should now be done!

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