Pull sbs into release branch

[pandora-kernel.git] / Documentation / power / swsusp.txt

diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt
index 0761ff6..aea7e92 100644 (file)
--- a/Documentation/power/swsusp.txt
+++ b/Documentation/power/swsusp.txt
@@ -48,7 +48,7 @@ before suspend (it is limited to 500 MB by default).
 
 Article about goals and implementation of Software Suspend for Linux
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Author: G\82ábor Kuti
+Author: G\82ábor Kuti
 Last revised: 2003-10-20 by Pavel Machek
 
 Idea and goals to achieve
@@ -140,24 +140,13 @@ should be sent to the mailing list available through the suspend2
 website, and not to the Linux Kernel Mailing List. We are working
 toward merging suspend2 into the mainline kernel.
 
-Q: A kernel thread must voluntarily freeze itself (call 'refrigerator').
-I found some kernel threads that don't do it, and they don't freeze
-so the system can't sleep. Is this a known behavior?
+Q: What is the freezing of tasks and why are we using it?
 
-A: All such kernel threads need to be fixed, one by one. Select the
-place where the thread is safe to be frozen (no kernel semaphores
-should be held at that point and it must be safe to sleep there), and
-add:
+A: The freezing of tasks is a mechanism by which user space processes and some
+kernel threads are controlled during hibernation or system-wide suspend (on some
+architectures).  See freezing-of-tasks.txt for details.
 
-       try_to_freeze();
-
-If the thread is needed for writing the image to storage, you should
-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 +155,8 @@ 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.
@@ -388,8 +374,8 @@ 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
@@ -397,6 +383,9 @@ safest thing is to unmount all filesystems on removable media (such USB,
 Firewire, CompactFlash, MMC, external SATA, or even IDE hotplug bays)
 before suspending; then remount them after resuming.
 
+There is a work-around for this problem.  For more information, see
+Documentation/usb/persist.txt.
+
 Q: I upgraded the kernel from 2.6.15 to 2.6.16. Both kernels were
 compiled with the similar configuration files. Anyway I found that
 suspend to disk (and resume) is much slower on 2.6.16 compared to