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

Brian Norris
2014-09-04T00:06:30Z

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 adds a companion sysfs file (/sys/power/pm_test_delay) that
allows user-space to configure how long the system waits in this test
state before resuming. It also updates the PM debugging documentation to
mention the new file.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
---
Documentation/power/basic-pm-debugging.txt | 14 ++++++++------
kernel/power/main.c | 27 +++++++++++++++++++++++++++
kernel/power/power.h | 5 +++++
kernel/power/suspend.c | 8 ++++++--
4 files changed, 46 insertions(+), 8 deletions(-)

diff --git a/Documentation/power/basic-pm-debugging.txt b/Documentation/power/basic-pm-debugging.txt
index edeecd447d23..bd9f27ae99fe 100644
--- 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
-/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.
+Then, the kernel will try to freeze processes, suspend devices, wait a few
+seconds (5 by default, but configurable via /sys/power/pm_test_delay), 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 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/main.c b/kernel/power/main.c
index 9a59d042ea84..4d242c8b43a0 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -73,6 +73,7 @@ power_attr(pm_async);

#ifdef CONFIG_PM_DEBUG
int pm_test_level = TEST_NONE;
+int pm_test_seconds = PM_TEST_DELAY_DEFAULT;

static const char * const pm_tests[__TEST_AFTER_LAST] = {
[TEST_NONE] = "none",
@@ -132,6 +133,31 @@ static ssize_t pm_test_store(struct kobject *kobj, struct kobj_attribute *attr,
}

power_attr(pm_test);
+
+static ssize_t pm_test_delay_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", pm_test_seconds);
+}
+
+static ssize_t pm_test_delay_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t n)
+{
+ int val;
+
+ if (kstrtoint(buf, 10, &val))
+ return -EINVAL;
+
+ if (val < 0)
+ return -EINVAL;
+
+ pm_test_seconds = val;
+
+ return n;
+}
+
+power_attr(pm_test_delay);
#endif /* CONFIG_PM_DEBUG */

#ifdef CONFIG_DEBUG_FS
@@ -601,6 +627,7 @@ static struct attribute * g[] = {
#endif
#ifdef CONFIG_PM_DEBUG
&pm_test_attr.attr,
+ &pm_test_delay_attr.attr,
#endif
#ifdef CONFIG_PM_SLEEP_DEBUG
&pm_print_times_attr.attr,
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 5d49dcac2537..28111795da71 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -230,6 +230,11 @@ enum {

extern int pm_test_level;

+/* Default to 5 second delay */
+#define PM_TEST_DELAY_DEFAULT 5
+
+extern int pm_test_seconds;
+
#ifdef CONFIG_SUSPEND_FREEZER
static inline int suspend_freeze_processes(void)
{
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 6dadb25cb0d8..2372a99d4356 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -196,8 +196,12 @@ 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);
+ int i;
+
+ pr_info("suspend debug: waiting for %d second(s)\n",
+ pm_test_seconds);
+ for (i = 0; i < pm_test_seconds; i++)
+ mdelay(1000);
return 1;
}
#endif /* !CONFIG_PM_DEBUG */
--
1.9.1