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 <computersforpe...@gmail.com>
---
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;
}
+#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 */
--
2.3.0
--
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