path: root/Documentation/power/basic-pm-debugging.txt
diff options
authorBrian Norris <computersforpeace@gmail.com>2015-02-22 21:16:49 -0800
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2015-02-26 01:21:26 +0100
commit1d4a9c17d4d204a159139361e8d4db7f9f267879 (patch)
treea419a5a715a3506e7972b556591b252f3b6ee10b /Documentation/power/basic-pm-debugging.txt
parentc517d838eb7d07bbe9507871fab3931deccff539 (diff)
PM / sleep: add configurable delay for pm_test
When CONFIG_PM_DEBUG=y, we provide a sysfs file (/sys/power/pm_test) for selecting one of a few suspend test modes, where rather than entering a full suspend state, the kernel will perform some subset of suspend steps, wait 5 seconds, and then resume back to normal operation. This mode is useful for (among other things) observing the state of the system just before entering a sleep mode, for debugging or analysis purposes. However, a constant 5 second wait is not sufficient for some sorts of analysis; for example, on an SoC, one might want to use external tools to probe the power states of various on-chip controllers or clocks. This patch turns this 5 second delay into a configurable module parameter, so users can determine how long to wait in this pseudo-suspend state before resuming the system. Example (wait 30 seconds); # echo 30 > /sys/module/suspend/parameters/pm_test_delay # echo core > /sys/power/pm_test # time echo mem > /sys/power/state ... [ 17.583625] suspend debug: Waiting for 30 second(s). ... real 0m30.381s user 0m0.017s sys 0m0.080s Signed-off-by: Brian Norris <computersforpeace@gmail.com> Acked-by: Pavel Machek <pavel@ucw.cz> Reviewed-by: Kevin Cernekee <cernekee@chromium.org> Acked-by: Florian Fainelli <f.fainelli@gmail.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/power/basic-pm-debugging.txt')
1 files changed, 6 insertions, 4 deletions
diff --git a/Documentation/power/basic-pm-debugging.txt b/Documentation/power/basic-pm-debugging.txt
index edeecd447d23..b96098ccfe69 100644
--- a/Documentation/power/basic-pm-debugging.txt
+++ b/Documentation/power/basic-pm-debugging.txt
@@ -75,12 +75,14 @@ you should do the following:
# echo platform > /sys/power/disk
# echo disk > /sys/power/state
-Then, the kernel will try to freeze processes, suspend devices, wait 5 seconds,
-resume devices and thaw processes. If "platform" is written to
+Then, the kernel will try to freeze processes, suspend devices, wait a few
+seconds (5 by default, but configurable by the suspend.pm_test_delay module
+parameter), resume devices and thaw processes. If "platform" is written to
/sys/power/pm_test , then after suspending devices the kernel will additionally
invoke the global control methods (eg. ACPI global control methods) used to
-prepare the platform firmware for hibernation. Next, it will wait 5 seconds and
-invoke the platform (eg. ACPI) global methods used to cancel hibernation etc.
+prepare the platform firmware for hibernation. Next, it will wait a
+configurable number of seconds and invoke the platform (eg. ACPI) global
+methods used to cancel hibernation etc.
Writing "none" to /sys/power/pm_test causes the kernel to switch to the normal
hibernation/suspend operations. Also, when open for reading, /sys/power/pm_test