path: root/Documentation
diff options
authorLinus Torvalds <>2013-05-16 15:12:34 -0700
committerLinus Torvalds <>2013-05-16 15:12:34 -0700
commitd5fe85af85367d5892e4308f596de4e2a5fb9017 (patch)
tree8f31a641a0e24c3ecb38dc1396665149ac4b4746 /Documentation
parent896821657479905b95d5193595b81679155ce199 (diff)
parent49a9e4315d40e1ba1d3258ea33f3948254038455 (diff)
Merge tag 'pm+acpi-3.10-rc2' of git://
Pull power management and ACPI fixes from Rafael Wysocki: - intel_pstate driver fixes and cleanups from Dirk Brandewie and Wei Yongjun. - cpufreq fixes related to ARM big.LITTLE support and the cpufreq-cpu0 driver from Viresh Kumar. - Assorted cpufreq fixes from Srivatsa S Bhat, Borislav Petkov, Wolfram Sang, Alexander Shiyan, and Nishanth Menon. - Assorted ACPI fixes from Catalin Marinas, Lan Tianyu, Alex Hung, Jan-Simon Möller, and Rafael J Wysocki. - Fix for a kfree() under spinlock in the PM core from Shuah Khan. - PM documentation updates from Borislav Petkov and Zhang Rui. * tag 'pm+acpi-3.10-rc2' of git:// (30 commits) cpufreq: Preserve sysfs files across suspend/resume ACPI / scan: Fix memory leak on acpi_scan_init_hotplug() error path PM / hibernate: Correct documentation PM / Documentation: remove inaccurate suspend/hibernate transition lantency statement PM: Documentation update for freeze state cpufreq / intel_pstate: use vzalloc() instead of vmalloc()/memset(0) cpufreq, ondemand: Remove leftover debug line PM: Avoid calling kfree() under spinlock in dev_pm_put_subsys_data() cpufreq / kirkwood: don't check resource with devm_ioremap_resource cpufreq / intel_pstate: remove #ifdef MODULE compile fence cpufreq / intel_pstate: Remove idle mode PID cpufreq / intel_pstate: fix ffmpeg regression cpufreq / intel_pstate: use lowest requested max performance cpufreq / intel_pstate: remove idle time and duration from sample and calculations cpufreq: Fix incorrect dependecies for ARM SA11xx drivers cpufreq: ARM big LITTLE: Fix Kconfig entries cpufreq: cpufreq-cpu0: Free parent node for error cases cpufreq: cpufreq-cpu0: defer probe when regulator is not ready cpufreq: Issue CPUFREQ_GOV_POLICY_EXIT notifier before dropping policy refcount cpufreq: governors: Fix CPUFREQ_GOV_POLICY_{INIT|EXIT} notifiers ...
Diffstat (limited to 'Documentation')
4 files changed, 31 insertions, 24 deletions
diff --git a/Documentation/power/devices.txt b/Documentation/power/devices.txt
index 504dfe4d52eb..a66c9821b5ce 100644
--- a/Documentation/power/devices.txt
+++ b/Documentation/power/devices.txt
@@ -268,7 +268,7 @@ situations.
System Power Management Phases
Suspending or resuming the system is done in several phases. Different phases
-are used for standby or memory sleep states ("suspend-to-RAM") and the
+are used for freeze, standby, and memory sleep states ("suspend-to-RAM") and the
hibernation state ("suspend-to-disk"). Each phase involves executing callbacks
for every device before the next phase begins. Not all busses or classes
support all these callbacks and not all drivers use all the callbacks. The
@@ -309,7 +309,8 @@ execute the corresponding method from dev->driver->pm instead if there is one.
Entering System Suspend
-When the system goes into the standby or memory sleep state, the phases are:
+When the system goes into the freeze, standby or memory sleep state,
+the phases are:
prepare, suspend, suspend_late, suspend_noirq.
@@ -368,7 +369,7 @@ the devices that were suspended.
Leaving System Suspend
-When resuming from standby or memory sleep, the phases are:
+When resuming from freeze, standby or memory sleep, the phases are:
resume_noirq, resume_early, resume, complete.
@@ -433,8 +434,8 @@ the system log.
Entering Hibernation
-Hibernating the system is more complicated than putting it into the standby or
-memory sleep state, because it involves creating and saving a system image.
+Hibernating the system is more complicated than putting it into the other
+sleep states, because it involves creating and saving a system image.
Therefore there are more phases for hibernation, with a different set of
callbacks. These phases always run after tasks have been frozen and memory has
been freed.
@@ -485,8 +486,8 @@ image forms an atomic snapshot of the system state.
At this point the system image is saved, and the devices then need to be
prepared for the upcoming system shutdown. This is much like suspending them
-before putting the system into the standby or memory sleep state, and the phases
-are similar.
+before putting the system into the freeze, standby or memory sleep state,
+and the phases are similar.
9. The prepare phase is discussed above.
diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt
index c537834af005..f1f0f59a7c47 100644
--- a/Documentation/power/interface.txt
+++ b/Documentation/power/interface.txt
@@ -7,8 +7,8 @@ running. The interface exists in /sys/power/ directory (assuming sysfs
is mounted at /sys).
/sys/power/state controls system power state. Reading from this file
-returns what states are supported, which is hard-coded to 'standby'
-(Power-On Suspend), 'mem' (Suspend-to-RAM), and 'disk'
+returns what states are supported, which is hard-coded to 'freeze',
+'standby' (Power-On Suspend), 'mem' (Suspend-to-RAM), and 'disk'
Writing to this file one of those strings causes the system to
diff --git a/Documentation/power/notifiers.txt b/Documentation/power/notifiers.txt
index c2a4a346c0d9..a81fa254303d 100644
--- a/Documentation/power/notifiers.txt
+++ b/Documentation/power/notifiers.txt
@@ -15,8 +15,10 @@ A suspend/hibernation notifier may be used for this purpose.
The subsystems or drivers having such needs can register suspend notifiers that
will be called upon the following events by the PM core:
-PM_HIBERNATION_PREPARE The system is going to hibernate or suspend, tasks will
- be frozen immediately.
+PM_HIBERNATION_PREPARE The system is going to hibernate, tasks will be frozen
+ immediately. This is different from PM_SUSPEND_PREPARE
+ below because here we do additional work between notifiers
+ and drivers freezing.
PM_POST_HIBERNATION The system memory state has been restored from a
hibernation image or an error occurred during
diff --git a/Documentation/power/states.txt b/Documentation/power/states.txt
index 4416b28630df..442d43df9b25 100644
--- a/Documentation/power/states.txt
+++ b/Documentation/power/states.txt
@@ -2,12 +2,26 @@
System Power Management States
-The kernel supports three power management states generically, though
-each is dependent on platform support code to implement the low-level
-details for each state. This file describes each state, what they are
+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
+state: Freeze / Low-Power Idle
+ACPI state: S0
+String: "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
+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
+support, or it can be used in addition to Suspend-to-RAM (memory sleep)
+to provide reduced resume latency.
State: Standby / Power-On Suspend
ACPI State: S1
@@ -22,9 +36,6 @@ 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.
-A transition from Standby to the On state should take about 1-2
State: Suspend-to-RAM
ACPI State: S3
@@ -42,9 +53,6 @@ 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.
-A transition from Suspend-to-RAM to the On state should take about
-3-5 seconds.
State: Suspend-to-disk
ACPI State: S4
@@ -74,7 +82,3 @@ 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).
-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