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Date:	Fri, 12 Dec 2014 18:55:30 -0800
From:	Brian Norris <computersforpeace@...il.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-pm@...r.kernel.org, Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>,
	Chirantan Ekbote <chirantan@...omium.org>
Subject: Re: [PATCH] PM / sleep: add configurable delay for pm_test

Hi Rafael,

On Wed, Sep 03, 2014 at 04:55:35PM -0700, Brian Norris wrote:
> 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@...il.com>

What do you think about this patch? It seems there is at least one other
developer who is independently interested in this.

Thanks,
Brian

> ---
>  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
> 
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