Diffstat (limited to 'Documentation')
3 files changed, 17 insertions, 31 deletions
diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt
index 74311d7e0f3c..8c5b41bf3f36 100644
@@ -18,17 +18,10 @@ states.
/sys/power/disk controls the operating mode of the suspend-to-disk
-mechanism. Suspend-to-disk can be handled in several ways. The
-greatest distinction is who writes memory to disk - the firmware or
-the kernel. If the firmware does it, we assume that it also handles
-suspending the system.
-If the kernel does it, then we have three options for putting the system
-to sleep - using the platform driver (e.g. ACPI or other PM
-registers), powering off the system or rebooting the system (for
-testing). The system will support either 'firmware' or 'platform', and
-that is known a priori. But, the user may choose 'shutdown' or
-'reboot' as alternatives.
+mechanism. Suspend-to-disk can be handled in several ways. We have a
+few options for putting the system to sleep - using the platform driver
+(e.g. ACPI or other pm_ops), powering off the system or rebooting the
+system (for testing).
Additionally, /sys/power/disk can be used to turn on one of the two testing
modes of the suspend-to-disk mechanism: 'testproc' or 'test'. If the
@@ -44,16 +37,12 @@ is being slow and which device drivers are misbehaving.
Reading from this file will display what the mode is currently set
to. Writing to this file will accept one of
+ 'platform' (only if the platform supports it)
-It will only change to 'firmware' or 'platform' if the system supports
/sys/power/image_size controls the size of the image created by
the suspend-to-disk mechanism. It can be written a string
representing a non-negative integer that will be used as an upper
diff --git a/Documentation/power/states.txt b/Documentation/power/states.txt
index 0931a330d362..34800cc521bf 100644
@@ -62,17 +62,18 @@ setup via another operating system for it to use. Despite the
inconvenience, this method requires minimal work by the kernel, since
the firmware will also handle restoring memory contents on resume.
-If the kernel is responsible for persistently saving state, a mechanism
-called 'swsusp' (Swap Suspend) is used to write memory contents to
-free swap space. swsusp has some restrictive requirements, but should
-work in most cases. Some, albeit outdated, documentation can be found
+For suspend-to-disk, a mechanism called swsusp called 'swsusp' (Swap
+Suspend) is used to write memory contents to free swap space.
+swsusp has some restrictive requirements, but should work in most
+cases. Some, albeit outdated, documentation can be found in
+Documentation/power/swsusp.txt. Alternatively, userspace can do most
+of the actual suspend to disk work, see userland-swsusp.txt.
Once memory state is written to disk, the system may either enter a
low-power state (like ACPI S4), or it may simply power down. Powering
down offers greater savings, and allows this mechanism to work on any
system. However, entering a real low-power state allows the user to
-trigger wake up events (e.g. pressing a key or opening a laptop lid).
+trigger wake up events (e.g. pressing a key or opening a laptop lid).
A transition from Suspend-to-Disk to the On state should take about 30
seconds, though it's typically a bit more with the current
diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt
index 0761ff6c57ed..c55bd5079b90 100644
@@ -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"?
@@ -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
-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
+"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
@@ -388,8 +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
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