[PATCH v2] PM / sleep: add configurable delay for pm_test

From: Brian Norris
Date: Sun Feb 22 2015 - 03:27:04 EST

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@xxxxxxxxx>
v2: - make this a module param instead of an explicit sysfs file
- drop the for loop; mdelay() does the same loop internally
- decrease +36 lines of code and +2 lines of doc, to +6 lines of code and
+2 lines of doc

kernel/power/suspend.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index c347e3ce3a55..aee23dab0a55 100644
--- 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"

@@ -204,12 +205,20 @@ static bool platform_suspend_again(suspend_state_t state)
suspend_ops->suspend_again() : false;

+static unsigned int pm_test_delay = 5;
+module_param(pm_test_delay, uint, 0644);
+ "Number of seconds to wait before resuming from suspend test");
static int suspend_test(int level)
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 */

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/