3 files changed, 83 insertions, 40 deletions

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index 64c9276..f455181 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -7,19 +7,30 @@ Description:
 		subsystem.
 
 What:		/sys/power/state
-Date:		August 2006
+Date:		May 2014
 Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
 Description:
-		The /sys/power/state file controls the system power state.
-		Reading from this file returns what states are supported,
-		which is hard-coded to 'freeze' (Low-Power Idle), 'standby'
-		(Power-On Suspend), 'mem' (Suspend-to-RAM), and 'disk'
-		(Suspend-to-Disk).
+		The /sys/power/state file controls system sleep states.
+		Reading from this file returns the available sleep state
+		labels, which may be "mem", "standby", "freeze" and "disk"
+		(hibernation).  The meanings of the first three labels depend on
+		the relative_sleep_states command line argument as follows:
+		 1) relative_sleep_states = 1
+		    "mem", "standby", "freeze" represent non-hibernation sleep
+		    states from the deepest ("mem", always present) to the
+		    shallowest ("freeze").  "standby" and "freeze" may or may
+		    not be present depending on the capabilities of the
+		    platform.  "freeze" can only be present if "standby" is
+		    present.
+		 2) relative_sleep_states = 0 (default)
+		    "mem" - "suspend-to-RAM", present if supported.
+		    "standby" - "power-on suspend", present if supported.
+		    "freeze" - "suspend-to-idle", always present.
 
 		Writing to this file one of these strings causes the system to
-		transition into that state. Please see the file
-		Documentation/power/states.txt for a description of each of
-		these states.
+		transition into the corresponding state, if available.  See
+		Documentation/power/states.txt for a description of what
+		"suspend-to-RAM", "power-on suspend" and "suspend-to-idle" mean.
 
 What:		/sys/power/disk
 Date:		September 2006
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4384217..e19a88b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2889,6 +2889,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			[KNL, SMP] Set scheduler's default relax_domain_level.
 			See Documentation/cgroups/cpusets.txt.
 
+	relative_sleep_states=
+			[SUSPEND] Use sleep state labeling where the deepest
+			state available other than hibernation is always "mem".
+			Format: { "0" | "1" }
+			0 -- Traditional sleep state labels.
+			1 -- Relative sleep state labels.
+
 	reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
 
 	reservetop=	[X86-32]
diff --git a/Documentation/power/states.txt b/Documentation/power/states.txt
index 442d43d..50f3ef9 100644
--- a/Documentation/power/states.txt
+++ b/Documentation/power/states.txt
@@ -1,62 +1,87 @@
+System Power Management Sleep States
 
-System Power Management States
+(C) 2014 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com>
 
+The kernel supports up to four system sleep states generically, although three
+of them depend on the platform support code to implement the low-level details
+for each state.
 
-The kernel supports four power management states generically, though
-one is generic and the other three are dependent on platform support
-code to implement the low-level details for each state.
-This file describes each state, what they are
-commonly called, what ACPI state they map to, and what string to write
-to /sys/power/state to enter that state
+The states are represented by strings that can be read or written to the
+/sys/power/state file.  Those strings may be "mem", "standby", "freeze" and
+"disk", where the last one always represents hibernation (Suspend-To-Disk) and
+the meaning of the remaining ones depends on the relative_sleep_states command
+line argument.
 
-state:		Freeze / Low-Power Idle
+For relative_sleep_states=1, the strings "mem", "standby" and "freeze" label the
+available non-hibernation sleep states from the deepest to the shallowest,
+respectively.  In that case, "mem" is always present in /sys/power/state,
+because there is at least one non-hibernation sleep state in every system.  If
+the given system supports two non-hibernation sleep states, "standby" is present
+in /sys/power/state in addition to "mem".  If the system supports three
+non-hibernation sleep states, "freeze" will be present in /sys/power/state in
+addition to "mem" and "standby".
+
+For relative_sleep_states=0, which is the default, the following descriptions
+apply.
+
+state:		Suspend-To-Idle
 ACPI state:	S0
-String:		"freeze"
+Label:		"freeze"
 
-This state is a generic, pure software, light-weight, low-power state.
-It allows more energy to be saved relative to idle by freezing user
+This state is a generic, pure software, light-weight, system sleep state.
+It allows more energy to be saved relative to runtime idle by freezing user
 space and putting all I/O devices into low-power states (possibly
 lower-power than available at run time), such that the processors can
 spend more time in their idle states.
-This state can be used for platforms without Standby/Suspend-to-RAM
+
+This state can be used for platforms without Power-On Suspend/Suspend-to-RAM
 support, or it can be used in addition to Suspend-to-RAM (memory sleep)
-to provide reduced resume latency.
+to provide reduced resume latency.  It is always supported.
 
 
 State:		Standby / Power-On Suspend
 ACPI State:	S1
-String:		"standby"
+Label:		"standby"
 
-This state offers minimal, though real, power savings, while providing
-a very low-latency transition back to a working system. No operating
-state is lost (the CPU retains power), so the system easily starts up
+This state, if supported, offers moderate, though real, power savings, while
+providing a relatively low-latency transition back to a working system.  No
+operating state is lost (the CPU retains power), so the system easily starts up
 again where it left off. 
 
-We try to put devices in a low-power state equivalent to D1, which
-also offers low power savings, but low resume latency. Not all devices
-support D1, and those that don't are left on. 
+In addition to freezing user space and putting all I/O devices into low-power
+states, which is done for Suspend-To-Idle too, nonboot CPUs are taken offline
+and all low-level system functions are suspended during transitions into this
+state.  For this reason, it should allow more energy to be saved relative to
+Suspend-To-Idle, but the resume latency will generally be greater than for that
+state.
 
 
 State:		Suspend-to-RAM
 ACPI State:	S3
-String:		"mem"
+Label:		"mem"
 
-This state offers significant power savings as everything in the
-system is put into a low-power state, except for memory, which is
-placed in self-refresh mode to retain its contents. 
+This state, if supported, offers significant power savings as everything in the
+system is put into a low-power state, except for memory, which should be placed
+into the self-refresh mode to retain its contents.  All of the steps carried out
+when entering Power-On Suspend are also carried out during transitions to STR.
+Additional operations may take place depending on the platform capabilities.  In
+particular, on ACPI systems the kernel passes control to the BIOS (platform
+firmware) as the last step during STR transitions and that usually results in
+powering down some more low-level components that aren't directly controlled by
+the kernel.
 
-System and device state is saved and kept in memory. All devices are
-suspended and put into D3. In many cases, all peripheral buses lose
-power when entering STR, so devices must be able to handle the
-transition back to the On state. 
+System and device state is saved and kept in memory.  All devices are suspended
+and put into low-power states.  In many cases, all peripheral buses lose power
+when entering STR, so devices must be able to handle the transition back to the
+"on" state.
 
-For at least ACPI, STR requires some minimal boot-strapping code to
-resume the system from STR. This may be true on other platforms. 
+For at least ACPI, STR requires some minimal boot-strapping code to resume the
+system from it.  This may be the case on other platforms too.
 
 
 State:		Suspend-to-disk
 ACPI State:	S4
-String:		"disk"
+Label:		"disk"
 
 This state offers the greatest power savings, and can be used even in
 the absence of low-level platform support for power management. This