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>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index bfcb1a62a7b48466f3cbe5a08d3e1a632eadc3d2..8b1fa5e129ac9a02bf3e5d1a02736bf897bf5ad8 100644 (file)
--- 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

diff --git a/Documentation/power/basic-pm-debugging.txt b/Documentation/power/basic-pm-debugging.txt
index edeecd447d23dc8ff26e66debe0d874b9482f087..b96098ccfe69208cf7491c1c4885563310398bf5 100644 (file)
--- 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

diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index b7d6b3a721b196ed581293a9a657ef54b7cb2798..8d7a1ef7275855089957f877d6743b653dd7f076 100644 (file)
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -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 */