Commit 1d4a9c17 authored by Brian Norris's avatar Brian Norris Committed by Rafael J. Wysocki
Browse files

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: default avatarBrian Norris <computersforpeace@gmail.com>
Acked-by: default avatarPavel Machek <pavel@ucw.cz>
Reviewed-by: default avatarKevin Cernekee <cernekee@chromium.org>
Acked-by: default avatarFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent c517d838

Documentation/kernel-parameters.txt

+7 −0
Original line number Diff line number Diff line
@@ -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

Documentation/power/basic-pm-debugging.txt

+6 −4
Original line number Diff line number Diff line
@@ -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

kernel/power/suspend.c

+11 −2
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <linux/ftrace.h>

#include <trace/events/power.h>

#include <linux/compiler.h>

#include <linux/moduleparam.h>



#include "power.h"
@@ -233,12 +234,20 @@ static bool platform_suspend_again(suspend_state_t state) 
		suspend_ops->suspend_again() : false;

}



#ifdef CONFIG_PM_DEBUG

static unsigned int pm_test_delay = 5;

module_param(pm_test_delay, uint, 0644);

MODULE_PARM_DESC(pm_test_delay,

		 "Number of seconds to wait before resuming from suspend test");

#endif



static int suspend_test(int level)

{

#ifdef CONFIG_PM_DEBUG

	if (pm_test_level == level) {

		printk(KERN_INFO "suspend debug: Waiting for 5 seconds.\n");

		mdelay(5000);

		printk(KERN_INFO "suspend debug: Waiting for %d second(s).\n",

				pm_test_delay);

		mdelay(pm_test_delay * 1000);

		return 1;

	}

#endif /* !CONFIG_PM_DEBUG */

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