Merge branch 'drm-patches' of master.kernel.org:/pub/scm/linux/kernel/git/airlied...

[linux-drm-fsl-dcu.git] / Documentation / power / swsusp.txt

diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt
index e635e6f1e316ca549834716c95fccc3c61b35748..c55bd5079b90e4ddc654fb8755e93bfca8144560 100644 (file)
--- a/Documentation/power/swsusp.txt
+++ b/Documentation/power/swsusp.txt
@@ -156,8 +156,7 @@ instead set the PF_NOFREEZE process flag when creating the thread (and
 be very careful).
 
 
-Q: What is the difference between "platform", "shutdown" and
-"firmware" in /sys/power/disk?
+Q: What is the difference between "platform" and "shutdown"?
 
 A:
 
@@ -166,11 +165,8 @@ shutdown: save state in linux, then tell bios to powerdown
 platform: save state in linux, then tell bios to powerdown and blink
           "suspended led"
 
-firmware: tell bios to save state itself [needs BIOS-specific suspend
-         partition, and has very little to do with swsusp]
-
-"platform" is actually right thing to do, but "shutdown" is most
-reliable.
+"platform" is actually right thing to do where supported, but
+"shutdown" is most reliable (except on ACPI systems).
 
 Q: I do not understand why you have such strong objections to idea of
 selective suspend.
@@ -297,20 +293,12 @@ system is shut down or suspended. Additionally use the encrypted
 suspend image to prevent sensitive data from being stolen after
 resume.
 
-Q: Why can't we suspend to a swap file?
-
-A: Because accessing swap file needs the filesystem mounted, and
-filesystem might do something wrong (like replaying the journal)
-during mount.
-
-There are few ways to get that fixed:
-
-1) Probably could be solved by modifying every filesystem to support
-some kind of "really read-only!" option. Patches welcome.
+Q: Can I suspend to a swap file?
 
-2) suspend2 gets around that by storing absolute positions in on-disk
-image (and blocksize), with resume parameter pointing directly to
-suspend header.
+A: Generally, yes, you can.  However, it requires you to use the "resume=" and
+"resume_offset=" kernel command line parameters, so the resume from a swap file
+cannot be initiated from an initrd or initramfs image.  See
+swsusp-and-swap-files.txt for details.
 
 Q: Is there a maximum system RAM size that is supported by swsusp?
 
@@ -396,8 +384,8 @@ while the system is asleep, maintaining the connection, using true sleep
 modes like "suspend-to-RAM" or "standby".  (Don't write "disk" to the
 /sys/power/state file; write "standby" or "mem".)  We've not seen any
 hardware that can use these modes through software suspend, although in
-theory some systems might support "platform" or "firmware" modes that
-won't break the USB connections.
+theory some systems might support "platform" modes that won't break the
+USB connections.
 
 Remember that it's always a bad idea to unplug a disk drive containing a
 mounted filesystem.  That's true even when your system is asleep!  The