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PM / sleep: add configurable delay for pm_test

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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 <[email protected]>
Acked-by: Pavel Machek <[email protected]>
Reviewed-by: Kevin Cernekee <[email protected]>
Acked-by: Florian Fainelli <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>
This commit is contained in:
Brian Norris 2015-02-22 21:16:49 -08:00 • committed by Rafael J. Wysocki
commit 1d4a9c17d4
3 changed files with 24 additions and 6 deletions
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10
Documentation/power/basic-pm-debugging.txt
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@ -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