Commit 543cc27d authored by Pavel Machek's avatar Pavel Machek Committed by Linus Torvalds
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[PATCH] swsusp: documentation updates

Update suspend-to-RAM documentation with new machines, and makes message
when processes can't be stopped little clearer.  (In one case, waiting
longer actually did help).

From: "Rafael J. Wysocki" <>

  Warn in the documentation that data may be lost if there are some
  filesystems mounted from USB devices before suspend.

  [Thanks to Alan Stern for providing the answer to the question in the
  Q:-A: part.]
Signed-off-by: default avatarPavel Machek <>
Signed-off-by: default avatarRafael J. Wysocki <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 74c7e2ef
......@@ -17,6 +17,11 @@ Some warnings, first.
* but it will probably only crash.
* (*) suspend/resume support is needed to make it safe.
* If you have any filesystems on USB devices mounted before suspend,
* they won't be accessible after resume and you may lose data, as though
* you have unplugged the USB devices with mounted filesystems on them
* (see the FAQ below for details).
You need to append resume=/dev/your_swap_partition to kernel command
line. Then you suspend by
......@@ -27,19 +32,18 @@ echo shutdown > /sys/power/disk; echo disk > /sys/power/state
echo platform > /sys/power/disk; echo disk > /sys/power/state
. If you have SATA disks, you'll need recent kernels with SATA suspend
support. For suspend and resume to work, make sure your disk drivers
are built into kernel -- not modules. [There's way to make
suspend/resume with modular disk drivers, see FAQ, but you probably
should not do that.]
If you want to limit the suspend image size to N bytes, do
echo N > /sys/power/image_size
before suspend (it is limited to 500 MB by default).
Encrypted suspend image:
If you want to store your suspend image encrypted with a temporary
key to prevent data gathering after resume you must compile
crypto and the aes algorithm into the kernel - modules won't work
as they cannot be loaded at resume time.
Article about goals and implementation of Software Suspend for Linux
......@@ -333,4 +337,37 @@ init=/bin/bash, then swapon and starting suspend sequence manually
usually does the trick. Then it is good idea to try with latest
vanilla kernel.
Q: How can distributions ship a swsusp-supporting kernel with modular
disk drivers (especially SATA)?
A: Well, it can be done, load the drivers, then do echo into
/sys/power/disk/resume file from initrd. Be sure not to mount
anything, not even read-only mount, or you are going to lose your
Q: How do I make suspend more verbose?
A: If you want to see any non-error kernel messages on the virtual
terminal the kernel switches to during suspend, you have to set the
kernel console loglevel to at least 5, for example by doing
echo 5 > /proc/sys/kernel/printk
Q: Is this true that if I have a mounted filesystem on a USB device and
I suspend to disk, I can lose data unless the filesystem has been mounted
with "sync"?
A: That's right. It depends on your hardware, and it could be true even for
suspend-to-RAM. In fact, even with "-o sync" you can lose data if your
programs have information in buffers they haven't written out to disk.
If you're lucky, your hardware will support low-power modes for USB
controllers while the system is asleep. Lots of hardware doesn't,
however. Shutting off the power to a USB controller is equivalent to
unplugging all the attached devices.
Remember that it's always a bad idea to unplug a disk drive containing a
mounted filesystem. With USB that's true even when your system is asleep!
The safest thing is to unmount all USB-based filesystems before suspending
and remount them after resuming.
Video issues with S3 resume
2003-2005, Pavel Machek
2003-2006, Pavel Machek
During S3 resume, hardware needs to be reinitialized. For most
devices, this is easy, and kernel driver knows how to do
......@@ -15,6 +15,27 @@ run normally so video card is normally initialized. It should not be
problem for S1 standby, because hardware should retain its state over
We either have to run video BIOS during early resume, or interpret it
using vbetool later, or maybe nothing is neccessary on particular
system because video state is preserved. Unfortunately different
methods work on different systems, and no known method suits all of
Userland application called s2ram has been developed; it contains long
whitelist of systems, and automatically selects working method for a
given system. It can be downloaded from CVS at . If you get a system that is not in the
whitelist, please try to find a working solution, and submit whitelist
entry so that work does not need to be repeated.
Currently, VBE_SAVE method (6 below) works on most
systems. Unfortunately, vbetool only runs after userland is resumed,
so it makes debugging of early resume problems
hard/impossible. Methods that do not rely on userland are preferable.
There are a few types of systems where video works after S3 resume:
(1) systems where video state is preserved over S3.
......@@ -104,6 +125,7 @@ HP NX7000 ??? (*)
HP Pavilion ZD7000 vbetool post needed, need open-source nv driver for X
HP Omnibook XE3 athlon version none (1)
HP Omnibook XE3GC none (1), video is S3 Savage/IX-MV
HP Omnibook 5150 none (1), (S1 also works OK)
IBM TP T20, model 2647-44G none (1), video is S3 Inc. 86C270-294 Savage/IX-MV, vesafb gets "interesting" but X work.
IBM TP A31 / Type 2652-M5G s3_mode (3) [works ok with BIOS 1.04 2002-08-23, but not at all with BIOS 1.11 2004-11-05 :-(]
IBM TP R32 / Type 2658-MMG none (1)
......@@ -120,18 +142,24 @@ IBM ThinkPad T42p (2373-GTG) s3_bios (2)
IBM TP X20 ??? (*)
IBM TP X30 s3_bios (2)
IBM TP X31 / Type 2672-XXH none (1), use radeontool ( to turn off backlight.
IBM TP X32 none (1), but backlight is on and video is trashed after long suspend
IBM TP X32 none (1), but backlight is on and video is trashed after long suspend. s3_bios,s3_mode (4) works too. Perhaps that gets better results?
IBM Thinkpad X40 Type 2371-7JG s3_bios,s3_mode (4)
IBM TP 600e none(1), but a switch to console and back to X is needed
Medion MD4220 ??? (*)
Samsung P35 vbetool needed (6)
Sharp PC-AR10 (ATI rage) none (1)
Sharp PC-AR10 (ATI rage) none (1), backlight does not switch off
Sony Vaio PCG-C1VRX/K s3_bios (2)
Sony Vaio PCG-F403 ??? (*)
Sony Vaio PCG-GRT995MP none (1), works with 'nv' X driver
Sony Vaio PCG-GR7/K none (1), but needs radeonfb, use radeontool ( to turn off backlight.
Sony Vaio PCG-N505SN ??? (*)
Sony Vaio vgn-s260 X or boot-radeon can init it (5)
Sony Vaio vgn-S580BH vga=normal, but suspend from X. Console will be blank unless you return to X.
Sony Vaio vgn-FS115B s3_bios (2),s3_mode (4)
Toshiba Libretto L5 none (1)
Toshiba Satellite 4030CDT s3_mode (3)
Toshiba Satellite 4080XCDT s3_mode (3)
Toshiba Portege 3020CT s3_mode (3)
Toshiba Satellite 4030CDT s3_mode (3) (S1 also works OK)
Toshiba Satellite 4080XCDT s3_mode (3) (S1 also works OK)
Toshiba Satellite 4090XCDT ??? (*)
Toshiba Satellite P10-554 s3_bios,s3_mode (4)(****)
Toshiba M30 (2) xor X with nvidia driver using internal AGP
......@@ -151,39 +179,3 @@ Asus A7V8X nVidia RIVA TNT2 model 64 s3_bios,s3_mode (4)
(***) To be tested with a newer kernel.
(****) Not with SMP kernel, UP only.
VBEtool details
(with thanks to Carl-Daniel Hailfinger)
First, boot into X and run the following script ONCE:
mkdir -p $statedir
chvt 2
sleep 1
vbetool vbestate save >$statedir/vbe
To suspend and resume properly, call the following script as root:
fuser /dev/tty$curcons 2>/dev/null|xargs ps -o comm= -p|grep -q X && chvt 2
cat /dev/vcsa >$statedir/vcsa
echo 3 >/proc/acpi/sleep
vbetool post
vbetool vbestate restore <$statedir/vbe
cat $statedir/vcsa >/dev/vcsa
rckbd restart
chvt $[curcons%6+1]
chvt $curcons
Unless you change your graphics card or other hardware configuration,
the state once saved will be OK for every resume afterwards.
NOTE: The "rckbd restart" command may be different for your
distribution. Simply replace it with the command you would use to
set the fonts on screen.
......@@ -83,7 +83,7 @@ int freeze_processes(void)
yield(); /* Yield is okay here */
if (todo && time_after(jiffies, start_time + TIMEOUT)) {
printk( "\n" );
printk(KERN_ERR " stopping tasks failed (%d tasks remaining)\n", todo );
printk(KERN_ERR " stopping tasks timed out (%d tasks remaining)\n", todo );
} while(todo);
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