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>

1 files changed, 7 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index bfcb1a62a7b4..8b1fa5e129ac 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3462,6 +3462,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         improve throughput, but will also increase the
                         amount of memory reserved for use by the client.
 
+        suspend.pm_test_delay=
+                        [SUSPEND]
+                        Sets the number of seconds to remain in a suspend test
+                        mode before resuming the system (see
+                        /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
+                        is set. Default value is 5.
+
         swapaccount=[0|1]
                         [KNL] Enable accounting of swap in memory resource
                         controller if no parameter or 1 is given or disable