PM: boot time suspend selftest

From: David Brownell <[email protected]>

Boot-time test for system suspend states (STR or standby). The generic RTC framework triggers wakeup alarms, which are used to exit those states.

- Measures some aspects of suspend time ... this uses "jiffies" until someone converts it to use a timebase that works properly even while timer IRQs are disabled.

- Triggered by a command line parameter. By default nothing even vaguely troublesome will happen, but "test_suspend=mem" will give you a brief STR test during system boot. (Or you may need to use "test_suspend=standby" instead, if your hardware needs that.)

This isn't without problems. It fires early enough during boot that for example both PCMCIA and MMC stacks have misbehaved. The workaround in those cases was to boot without such media cards inserted.

Signed-off-by David Brownell <[email protected]>

---
I've used this on some ARM boards, and Ingo says it's been a big help avoiding (upstream) regressions for x86.git work. Based on some early work from Pavel, who wanted a pony. ;)

 Documentation/kernel-parameters.txt |    9 +
 kernel/power/Kconfig                |   11 ++
 kernel/power/main.c                 |  185 ++++++++++++++++++++++++++++++++++
 3 files changed, 204 insertions(+), 1 deletion(-)

Documentation/kernel-parameters.txt +8 -1

@@ -87,7 +87,8 @@ parameter is applicable:
 	SH	SuperH architecture is enabled.
 	SMP	The kernel is an SMP kernel.
 	SPARC	Sparc architecture is enabled.
-	SWSUSP	Software suspend is enabled.
+	SWSUSP	Software suspend (hibernation) is enabled.
+	SUSPEND	System suspend states are enabled.
 	TS	Appropriate touchscreen support is enabled.
 	USB	USB support is enabled.
 	USBHID	USB Human Interface Device support is enabled.

@@ -2035,6 +2036,12 @@ and is between 256 and 4096 characters. 
 
 	tdfx=		[HW,DRM]
 
+	test_suspend=	[SUSPEND]
+			Specify "mem" (for Suspend-to-RAM) or "standby" (for
+			standby suspend) as the system sleep state to briefly
+			enter during system startup.  The system is woken from
+			this state using a wakeup-capable RTC alarm.
+
 	thash_entries=	[KNL,NET]
 			Set number of hash buckets for TCP connection
 

kernel/power/Kconfig +11 -0

@@ -94,6 +94,17 @@ config SUSPEND
 	  powered and thus its contents are preserved, such as the
 	  suspend-to-RAM state (e.g. the ACPI S3 state).
 
+config PM_TEST_SUSPEND
+	bool "Test suspend/resume and wakealarm during bootup"
+	depends on SUSPEND && PM_DEBUG && RTC_LIB=y
+	---help---
+	This option will let you suspend your machine during bootup, and
+	make it wake up a few seconds later using an RTC wakeup alarm.
+	Enable this with a kernel parameter like "test_suspend=mem".
+
+	You probably want to have your system's RTC driver statically
+	linked, ensuring that it's available when this test runs.
+
 config SUSPEND_FREEZER
 	bool "Enable freezer for suspend to RAM/standby" \
 		if ARCH_WANTS_FREEZER_CONTROL || BROKEN

kernel/power/main.c +185 -0

@@ -132,6 +132,52 @@ static inline int suspend_test(int level
 
 #ifdef CONFIG_SUSPEND
 
+#ifdef CONFIG_PM_TEST_SUSPEND
+
+/*
+ * We test the system suspend code by setting an RTC wakealarm a short
+ * time in the future, then suspending.  Suspending the devices won't
+ * normally take long ... some systems only need a few milliseconds.
+ *
+ * The time it takes is system-specific though, so when we test this
+ * during system bootup we allow a LOT of time.
+ */
+#define TEST_SUSPEND_SECONDS	5
+
+static unsigned long suspend_test_start_time;
+
+static void suspend_test_start(void)
+{
+	/* FIXME Use better timebase than "jiffies", ideally a clocksource.
+	 * What we want is a hardware counter that will work correctly even
+	 * during the irqs-are-off stages of the suspend/resume cycle...
+	 */
+	suspend_test_start_time = jiffies;
+}
+
+static void suspend_test_finish(const char *label)
+{
+	long nj = jiffies - suspend_test_start_time;
+	unsigned msec;
+
+	msec = jiffies_to_msecs((nj >= 0) ? nj : -nj);
+	pr_info("PM: %s took %d.%03d seconds\n", label,
+			msec / 1000, msec % 1000);
+	WARN_ON_ONCE(msec > (TEST_SUSPEND_SECONDS * 1000));
+}
+
+#else
+
+static void suspend_test_start(void)
+{
+}
+
+static void suspend_test_finish(const char *label)
+{
+}
+
+#endif
+
 /* This is just an arbitrary number */
 #define FREE_PAGE_NUMBER (100)
 

@@ -264,11 +310,14 @@ int suspend_devices_and_enter(suspend_st
 			goto Close;
 	}
 	suspend_console();
+
+	suspend_test_start();
 	error = device_suspend(PMSG_SUSPEND);
 	if (error) {
 		printk(KERN_ERR "PM: Some devices failed to suspend\n");
 		goto Resume_console;
 	}
+	suspend_test_finish("suspend devices");
 
 	if (suspend_test(TEST_DEVICES))
 		goto Resume_devices;

@@ -291,7 +340,9 @@ int suspend_devices_and_enter(suspend_st
 	if (suspend_ops->finish)
 		suspend_ops->finish();
  Resume_devices:
+	suspend_test_start();
 	device_resume();
+	suspend_test_finish("resume devices");
  Resume_console:
 	resume_console();
  Close:

@@ -515,3 +566,137 @@ static int __init pm_init(void)
 }
 
 core_initcall(pm_init);
+
+
+#ifdef CONFIG_PM_TEST_SUSPEND
+
+#include <linux/rtc.h>
+
+/*
+ * To test system suspend, we need a hands-off mechanism to resume the
+ * system.  RTCs wake alarms are a common self-contained mechanism.
+ */
+
+static void __init test_wakealarm(struct rtc_device *rtc, suspend_state_t state)
+{
+	static char		err_readtime [] __initdata =
+		KERN_ERR "PM: can't read %s time, err %d\n";
+	static char		err_wakealarm [] __initdata =
+		KERN_ERR "PM: can't set %s wakealarm, err %d\n";
+	static char		err_suspend [] __initdata =
+		KERN_ERR "PM: suspend test failed, error %d\n";
+	static char		info_test [] __initdata =
+		KERN_INFO "PM: test RTC wakeup from '%s' suspend\n";
+
+	unsigned long		now;
+	struct rtc_wkalrm	alm;
+	int			status;
+
+	/* this may fail if the RTC hasn't been initialized */
+	status = rtc_read_time(rtc, &alm.time);
+	if (status < 0) {
+		printk(err_readtime, rtc->dev.bus_id, status);
+		return;
+	}
+	rtc_tm_to_time(&alm.time, &now);
+
+	memset(&alm, 0, sizeof alm);
+	rtc_time_to_tm(now + TEST_SUSPEND_SECONDS, &alm.time);
+	alm.enabled = true;
+
+	status = rtc_set_alarm(rtc, &alm);
+	if (status < 0) {
+		printk(err_wakealarm, rtc->dev.bus_id, status);
+		return;
+	}
+
+	if (state == PM_SUSPEND_MEM) {
+		printk(info_test, pm_states[state]);
+		status = pm_suspend(state);
+		if (status == -ENODEV)
+			state = PM_SUSPEND_STANDBY;
+	}
+	if (state == PM_SUSPEND_STANDBY) {
+		printk(info_test, pm_states[state]);
+		status = pm_suspend(state);
+	}
+	if (status < 0)
+		printk(err_suspend, status);
+}
+
+static int __init has_wakealarm(struct device *dev, void *name_ptr)
+{
+	struct rtc_device *candidate = to_rtc_device(dev);
+
+	if (!candidate->ops->set_alarm)
+		return 0;
+	if (!device_may_wakeup(candidate->dev.parent))
+		return 0;
+
+	*(char **)name_ptr = dev->bus_id;
+	return 1;
+}
+
+/*
+ * Kernel options like "test_suspend=mem" force suspend/resume sanity tests
+ * at startup time.  They're normally disabled, for faster boot and because
+ * we can't know which states really work on this particular system.
+ */
+static suspend_state_t test_state __initdata = PM_SUSPEND_ON;
+
+static char warn_bad_state[] __initdata =
+	KERN_WARNING "PM: can't test '%s' suspend state\n";
+
+static int __init setup_test_suspend(char *value)
+{
+	unsigned i;
+
+	/* "=mem" ==> "mem" */
+	value++;
+	for (i = 0; i < PM_SUSPEND_MAX; i++) {
+		if (!pm_states[i])
+			continue;
+		if (strcmp(pm_states[i], value) != 0)
+			continue;
+		test_state = (__force suspend_state_t) i;
+		return 0;
+	}
+	printk(warn_bad_state, value);
+	return 0;
+}
+__setup("test_suspend", setup_test_suspend);
+
+static int __init test_suspend(void)
+{
+	static char		warn_no_rtc[] __initdata =
+		KERN_WARNING "PM: no wakealarm-capable RTC driver is ready\n";
+
+	char			*pony = NULL;
+	struct rtc_device	*rtc = NULL;
+
+	/* PM is initialized by now; is that state testable? */
+	if (test_state == PM_SUSPEND_ON)
+		goto done;
+	if (!valid_state(test_state)) {
+		printk(warn_bad_state, pm_states[test_state]);
+		goto done;
+	}
+
+	/* RTCs have initialized by now too ... can we use one? */
+	class_find_device(rtc_class, &pony, has_wakealarm);
+	if (pony)
+		rtc = rtc_class_open(pony);
+	if (!rtc) {
+		printk(warn_no_rtc);
+		goto done;
+	}
+
+	/* go for it */
+	test_wakealarm(rtc, test_state);
+	rtc_class_close(rtc);
+done:
+	return 0;
+}
+late_initcall(test_suspend);
+
+#endif /* CONFIG_PM_TEST_SUSPEND */

Two questions:

1) How is it related to the analogous patch in the Ingo's tree?

2) Does it apply to the current linux-next?

Two questions:

1) How is it related to the analogous patch in the Ingo's tree?

2) Does it apply to the current linux-next?

Quoted 3 lines · Rafael J. Wysocki

Two questions:

1) How is it related to the analogous patch in the Ingo's tree?

AFAIK -- just that it's an updated version. Comments, some code flow, but mostly having the "test_suspend=mode" parameter default to "safe -- no testing" and allows the choice of modes.

Quoted 1 line

2) Does it apply to the current linux-next?

No idea.

Quoted 10 lines · David Brownell

Quoted 3 lines · Rafael J. Wysocki

Two questions:

1) How is it related to the analogous patch in the Ingo's tree?

AFAIK -- just that it's an updated version. Comments, some code flow, but mostly having the "test_suspend=mode" parameter default to "safe -- no testing" and allows the choice of modes.

Quoted 3 lines

Quoted 1 line

2) Does it apply to the current linux-next?

No idea.

Could you check, please? The previous version didn't.

Quoted 3 lines

Could you check, please?  The previous version didn't.

There's just one trivial reject against the PCI tree's pm-introduce-new-top-level-suspend-and-hibernation-callbacks:

***************
*** 293,299 ****
        if (suspend_ops->finish)
                suspend_ops->finish();
   Resume_devices:
        device_resume();
   Resume_console:
        resume_console();
   Close:
--- 342,350 ----
        if (suspend_ops->finish)
                suspend_ops->finish();
   Resume_devices:
+       suspend_test_start();
        device_resume();
+       suspend_test_finish("resume devices");
   Resume_console:
        resume_console();
   Close:

Quoted 3 lines

Could you check, please?  The previous version didn't.

There's just one trivial reject against the PCI tree's pm-introduce-new-top-level-suspend-and-hibernation-callbacks:

***************
*** 293,299 ****
        if (suspend_ops->finish)
                suspend_ops->finish();
   Resume_devices:
        device_resume();
   Resume_console:
        resume_console();
   Close:
--- 342,350 ----
        if (suspend_ops->finish)
                suspend_ops->finish();
   Resume_devices:
+       suspend_test_start();
        device_resume();
+       suspend_test_finish("resume devices");
   Resume_console:
        resume_console();
   Close:

Quoted 3 lines · Rafael J. Wysocki

Two questions:

1) How is it related to the analogous patch in the Ingo's tree?

AFAIK -- just that it's an updated version. Comments, some code flow, but mostly having the "test_suspend=mode" parameter default to "safe -- no testing" and allows the choice of modes.

Quoted 1 line

2) Does it apply to the current linux-next?

No idea.

From: David Brownell <[email protected]>

Boot-time test for system suspend states (STR or standby). The generic RTC framework triggers wakeup alarms, which are used to exit those states.

- Measures some aspects of suspend time ... this uses "jiffies" until someone converts it to use a timebase that works properly even while timer IRQs are disabled.

- Triggered by a command line parameter. By default nothing even vaguely troublesome will happen, but "test_suspend=mem" will give you a brief STR test during system boot. (Or you may need to use "test_suspend=standby" instead, if your hardware needs that.)

This isn't without problems. It fires early enough during boot that for example both PCMCIA and MMC stacks have misbehaved. The workaround in those cases was to boot without such media cards inserted.

Signed-off-by David Brownell <[email protected]>

---
I've used this on some ARM boards, and Ingo says it's been a big help avoiding (upstream) regressions for x86.git work. Based on some early work from Pavel, who wanted a pony. ;)

 Documentation/kernel-parameters.txt |    9 +
 kernel/power/Kconfig                |   11 ++
 kernel/power/main.c                 |  185 ++++++++++++++++++++++++++++++++++
 3 files changed, 204 insertions(+), 1 deletion(-)

Documentation/kernel-parameters.txt +8 -1

@@ -87,7 +87,8 @@ parameter is applicable:
 	SH	SuperH architecture is enabled.
 	SMP	The kernel is an SMP kernel.
 	SPARC	Sparc architecture is enabled.
-	SWSUSP	Software suspend is enabled.
+	SWSUSP	Software suspend (hibernation) is enabled.
+	SUSPEND	System suspend states are enabled.
 	TS	Appropriate touchscreen support is enabled.
 	USB	USB support is enabled.
 	USBHID	USB Human Interface Device support is enabled.

@@ -2035,6 +2036,12 @@ and is between 256 and 4096 characters. 
 
 	tdfx=		[HW,DRM]
 
+	test_suspend=	[SUSPEND]
+			Specify "mem" (for Suspend-to-RAM) or "standby" (for
+			standby suspend) as the system sleep state to briefly
+			enter during system startup.  The system is woken from
+			this state using a wakeup-capable RTC alarm.
+
 	thash_entries=	[KNL,NET]
 			Set number of hash buckets for TCP connection
 

kernel/power/Kconfig +11 -0

@@ -94,6 +94,17 @@ config SUSPEND
 	  powered and thus its contents are preserved, such as the
 	  suspend-to-RAM state (e.g. the ACPI S3 state).
 
+config PM_TEST_SUSPEND
+	bool "Test suspend/resume and wakealarm during bootup"
+	depends on SUSPEND && PM_DEBUG && RTC_LIB=y
+	---help---
+	This option will let you suspend your machine during bootup, and
+	make it wake up a few seconds later using an RTC wakeup alarm.
+	Enable this with a kernel parameter like "test_suspend=mem".
+
+	You probably want to have your system's RTC driver statically
+	linked, ensuring that it's available when this test runs.
+
 config SUSPEND_FREEZER
 	bool "Enable freezer for suspend to RAM/standby" \
 		if ARCH_WANTS_FREEZER_CONTROL || BROKEN

kernel/power/main.c +185 -0

@@ -132,6 +132,52 @@ static inline int suspend_test(int level
 
 #ifdef CONFIG_SUSPEND
 
+#ifdef CONFIG_PM_TEST_SUSPEND
+
+/*
+ * We test the system suspend code by setting an RTC wakealarm a short
+ * time in the future, then suspending.  Suspending the devices won't
+ * normally take long ... some systems only need a few milliseconds.
+ *
+ * The time it takes is system-specific though, so when we test this
+ * during system bootup we allow a LOT of time.
+ */
+#define TEST_SUSPEND_SECONDS	5
+
+static unsigned long suspend_test_start_time;
+
+static void suspend_test_start(void)
+{
+	/* FIXME Use better timebase than "jiffies", ideally a clocksource.
+	 * What we want is a hardware counter that will work correctly even
+	 * during the irqs-are-off stages of the suspend/resume cycle...
+	 */
+	suspend_test_start_time = jiffies;
+}
+
+static void suspend_test_finish(const char *label)
+{
+	long nj = jiffies - suspend_test_start_time;
+	unsigned msec;
+
+	msec = jiffies_to_msecs((nj >= 0) ? nj : -nj);
+	pr_info("PM: %s took %d.%03d seconds\n", label,
+			msec / 1000, msec % 1000);
+	WARN_ON_ONCE(msec > (TEST_SUSPEND_SECONDS * 1000));
+}
+
+#else
+
+static void suspend_test_start(void)
+{
+}
+
+static void suspend_test_finish(const char *label)
+{
+}
+
+#endif
+
 /* This is just an arbitrary number */
 #define FREE_PAGE_NUMBER (100)
 

@@ -264,11 +310,14 @@ int suspend_devices_and_enter(suspend_st
 			goto Close;
 	}
 	suspend_console();
+
+	suspend_test_start();
 	error = device_suspend(PMSG_SUSPEND);
 	if (error) {
 		printk(KERN_ERR "PM: Some devices failed to suspend\n");
 		goto Resume_console;
 	}
+	suspend_test_finish("suspend devices");
 
 	if (suspend_test(TEST_DEVICES))
 		goto Resume_devices;

@@ -291,7 +340,9 @@ int suspend_devices_and_enter(suspend_st
 	if (suspend_ops->finish)
 		suspend_ops->finish();
  Resume_devices:
+	suspend_test_start();
 	device_resume();
+	suspend_test_finish("resume devices");
  Resume_console:
 	resume_console();
  Close:

@@ -515,3 +566,137 @@ static int __init pm_init(void)
 }
 
 core_initcall(pm_init);
+
+
+#ifdef CONFIG_PM_TEST_SUSPEND
+
+#include <linux/rtc.h>
+
+/*
+ * To test system suspend, we need a hands-off mechanism to resume the
+ * system.  RTCs wake alarms are a common self-contained mechanism.
+ */
+
+static void __init test_wakealarm(struct rtc_device *rtc, suspend_state_t state)
+{
+	static char		err_readtime [] __initdata =
+		KERN_ERR "PM: can't read %s time, err %d\n";
+	static char		err_wakealarm [] __initdata =
+		KERN_ERR "PM: can't set %s wakealarm, err %d\n";
+	static char		err_suspend [] __initdata =
+		KERN_ERR "PM: suspend test failed, error %d\n";
+	static char		info_test [] __initdata =
+		KERN_INFO "PM: test RTC wakeup from '%s' suspend\n";
+
+	unsigned long		now;
+	struct rtc_wkalrm	alm;
+	int			status;
+
+	/* this may fail if the RTC hasn't been initialized */
+	status = rtc_read_time(rtc, &alm.time);
+	if (status < 0) {
+		printk(err_readtime, rtc->dev.bus_id, status);
+		return;
+	}
+	rtc_tm_to_time(&alm.time, &now);
+
+	memset(&alm, 0, sizeof alm);
+	rtc_time_to_tm(now + TEST_SUSPEND_SECONDS, &alm.time);
+	alm.enabled = true;
+
+	status = rtc_set_alarm(rtc, &alm);
+	if (status < 0) {
+		printk(err_wakealarm, rtc->dev.bus_id, status);
+		return;
+	}
+
+	if (state == PM_SUSPEND_MEM) {
+		printk(info_test, pm_states[state]);
+		status = pm_suspend(state);
+		if (status == -ENODEV)
+			state = PM_SUSPEND_STANDBY;
+	}
+	if (state == PM_SUSPEND_STANDBY) {
+		printk(info_test, pm_states[state]);
+		status = pm_suspend(state);
+	}
+	if (status < 0)
+		printk(err_suspend, status);
+}
+
+static int __init has_wakealarm(struct device *dev, void *name_ptr)
+{
+	struct rtc_device *candidate = to_rtc_device(dev);
+
+	if (!candidate->ops->set_alarm)
+		return 0;
+	if (!device_may_wakeup(candidate->dev.parent))
+		return 0;
+
+	*(char **)name_ptr = dev->bus_id;
+	return 1;
+}
+
+/*
+ * Kernel options like "test_suspend=mem" force suspend/resume sanity tests
+ * at startup time.  They're normally disabled, for faster boot and because
+ * we can't know which states really work on this particular system.
+ */
+static suspend_state_t test_state __initdata = PM_SUSPEND_ON;
+
+static char warn_bad_state[] __initdata =
+	KERN_WARNING "PM: can't test '%s' suspend state\n";
+
+static int __init setup_test_suspend(char *value)
+{
+	unsigned i;
+
+	/* "=mem" ==> "mem" */
+	value++;
+	for (i = 0; i < PM_SUSPEND_MAX; i++) {
+		if (!pm_states[i])
+			continue;
+		if (strcmp(pm_states[i], value) != 0)
+			continue;
+		test_state = (__force suspend_state_t) i;
+		return 0;
+	}
+	printk(warn_bad_state, value);
+	return 0;
+}
+__setup("test_suspend", setup_test_suspend);
+
+static int __init test_suspend(void)
+{
+	static char		warn_no_rtc[] __initdata =
+		KERN_WARNING "PM: no wakealarm-capable RTC driver is ready\n";
+
+	char			*pony = NULL;
+	struct rtc_device	*rtc = NULL;
+
+	/* PM is initialized by now; is that state testable? */
+	if (test_state == PM_SUSPEND_ON)
+		goto done;
+	if (!valid_state(test_state)) {
+		printk(warn_bad_state, pm_states[test_state]);
+		goto done;
+	}
+
+	/* RTCs have initialized by now too ... can we use one? */
+	class_find_device(rtc_class, &pony, has_wakealarm);
+	if (pony)
+		rtc = rtc_class_open(pony);
+	if (!rtc) {
+		printk(warn_no_rtc);
+		goto done;
+	}
+
+	/* go for it */
+	test_wakealarm(rtc, test_state);
+	rtc_class_close(rtc);
+done:
+	return 0;
+}
+late_initcall(test_suspend);
+
+#endif /* CONFIG_PM_TEST_SUSPEND */

From: David Brownell <[email protected]>

Boot-time test for system suspend states (STR or standby). The generic RTC framework triggers wakeup alarms, which are used to exit those states.

- Measures some aspects of suspend time ... this uses "jiffies" until someone converts it to use a timebase that works properly even while timer IRQs are disabled.

- Triggered by a command line parameter. By default nothing even vaguely troublesome will happen, but "test_suspend=mem" will give you a brief STR test during system boot. (Or you may need to use "test_suspend=standby" instead, if your hardware needs that.)

This isn't without problems. It fires early enough during boot that for example both PCMCIA and MMC stacks have misbehaved. The workaround in those cases was to boot without such media cards inserted.

...

kernel/power/main.c +19 -0

+#ifdef CONFIG_PM_TEST_SUSPEND
+
+/*
+ * We test the system suspend code by setting an RTC wakealarm a short
+ * time in the future, then suspending.  Suspending the devices won't
+ * normally take long ... some systems only need a few milliseconds.
+ *
+ * The time it takes is system-specific though, so when we test this
+ * during system bootup we allow a LOT of time.
+ */
+#define TEST_SUSPEND_SECONDS	5
+
+static unsigned long suspend_test_start_time;
+
+static void suspend_test_start(void)
+{
+	/* FIXME Use better timebase than "jiffies", ideally a clocksource.
+	 * What we want is a hardware counter that will work correctly even
+	 * during the irqs-are-off stages of the suspend/resume cycle...

kernel/power/main.c +13 -0

+}
+
+#else
+
+static void suspend_test_start(void)
+{
+}
+
+static void suspend_test_finish(const char *label)
+{
+}
+
+#endif
 
...
 

kernel/power/main.c +61 -0

+	unsigned long		now;
+	struct rtc_wkalrm	alm;
+	int			status;
+
+	/* this may fail if the RTC hasn't been initialized */
+	status = rtc_read_time(rtc, &alm.time);
+	if (status < 0) {
+		printk(err_readtime, rtc->dev.bus_id, status);
+		return;
+	}
+	rtc_tm_to_time(&alm.time, &now);
+
+	memset(&alm, 0, sizeof alm);
+	rtc_time_to_tm(now + TEST_SUSPEND_SECONDS, &alm.time);
+	alm.enabled = true;
+
+	status = rtc_set_alarm(rtc, &alm);
+	if (status < 0) {
+		printk(err_wakealarm, rtc->dev.bus_id, status);
+		return;
+	}
+
+	if (state == PM_SUSPEND_MEM) {
+		printk(info_test, pm_states[state]);
+		status = pm_suspend(state);
+		if (status == -ENODEV)
+			state = PM_SUSPEND_STANDBY;
+	}
+	if (state == PM_SUSPEND_STANDBY) {
+		printk(info_test, pm_states[state]);
+		status = pm_suspend(state);
+	}
+	if (status < 0)
+		printk(err_suspend, status);
+}
+
+static int __init has_wakealarm(struct device *dev, void *name_ptr)
+{
+	struct rtc_device *candidate = to_rtc_device(dev);
+
+	if (!candidate->ops->set_alarm)
+		return 0;
+	if (!device_may_wakeup(candidate->dev.parent))
+		return 0;
+
+	*(char **)name_ptr = dev->bus_id;
+	return 1;
+}
+
+/*
+ * Kernel options like "test_suspend=mem" force suspend/resume sanity tests
+ * at startup time.  They're normally disabled, for faster boot and because
+ * we can't know which states really work on this particular system.
+ */
+static suspend_state_t test_state __initdata = PM_SUSPEND_ON;
+
+static char warn_bad_state[] __initdata =
+	KERN_WARNING "PM: can't test '%s' suspend state\n";
+
+static int __init setup_test_suspend(char *value)
+{

kernel/power/main.c +27 -0

+	struct rtc_device	*rtc = NULL;
+
+	/* PM is initialized by now; is that state testable? */
+	if (test_state == PM_SUSPEND_ON)
+		goto done;
+	if (!valid_state(test_state)) {
+		printk(warn_bad_state, pm_states[test_state]);
+		goto done;
+	}
+
+	/* RTCs have initialized by now too ... can we use one? */
+	class_find_device(rtc_class, &pony, has_wakealarm);
+	if (pony)
+		rtc = rtc_class_open(pony);
+	if (!rtc) {
+		printk(warn_no_rtc);
+		goto done;
+	}
+
+	/* go for it */
+	test_wakealarm(rtc, test_state);
+	rtc_class_close(rtc);
+done:
+	return 0;
+}
+late_initcall(test_suspend);
+

From: David Brownell <[email protected]>

Boot-time test for system suspend states (STR or standby). The generic RTC framework triggers wakeup alarms, which are used to exit those states.

- Measures some aspects of suspend time ... this uses "jiffies" until someone converts it to use a timebase that works properly even while timer IRQs are disabled.

- Triggered by a command line parameter. By default nothing even vaguely troublesome will happen, but "test_suspend=mem" will give you a brief STR test during system boot. (Or you may need to use "test_suspend=standby" instead, if your hardware needs that.)

This isn't without problems. It fires early enough during boot that for example both PCMCIA and MMC stacks have misbehaved. The workaround in those cases was to boot without such media cards inserted.

...

kernel/power/main.c +19 -0

+#ifdef CONFIG_PM_TEST_SUSPEND
+
+/*
+ * We test the system suspend code by setting an RTC wakealarm a short
+ * time in the future, then suspending.  Suspending the devices won't
+ * normally take long ... some systems only need a few milliseconds.
+ *
+ * The time it takes is system-specific though, so when we test this
+ * during system bootup we allow a LOT of time.
+ */
+#define TEST_SUSPEND_SECONDS	5
+
+static unsigned long suspend_test_start_time;
+
+static void suspend_test_start(void)
+{
+	/* FIXME Use better timebase than "jiffies", ideally a clocksource.
+	 * What we want is a hardware counter that will work correctly even
+	 * during the irqs-are-off stages of the suspend/resume cycle...

kernel/power/main.c +13 -0

+}
+
+#else
+
+static void suspend_test_start(void)
+{
+}
+
+static void suspend_test_finish(const char *label)
+{
+}
+
+#endif
 
...
 

kernel/power/main.c +61 -0

+	unsigned long		now;
+	struct rtc_wkalrm	alm;
+	int			status;
+
+	/* this may fail if the RTC hasn't been initialized */
+	status = rtc_read_time(rtc, &alm.time);
+	if (status < 0) {
+		printk(err_readtime, rtc->dev.bus_id, status);
+		return;
+	}
+	rtc_tm_to_time(&alm.time, &now);
+
+	memset(&alm, 0, sizeof alm);
+	rtc_time_to_tm(now + TEST_SUSPEND_SECONDS, &alm.time);
+	alm.enabled = true;
+
+	status = rtc_set_alarm(rtc, &alm);
+	if (status < 0) {
+		printk(err_wakealarm, rtc->dev.bus_id, status);
+		return;
+	}
+
+	if (state == PM_SUSPEND_MEM) {
+		printk(info_test, pm_states[state]);
+		status = pm_suspend(state);
+		if (status == -ENODEV)
+			state = PM_SUSPEND_STANDBY;
+	}
+	if (state == PM_SUSPEND_STANDBY) {
+		printk(info_test, pm_states[state]);
+		status = pm_suspend(state);
+	}
+	if (status < 0)
+		printk(err_suspend, status);
+}
+
+static int __init has_wakealarm(struct device *dev, void *name_ptr)
+{
+	struct rtc_device *candidate = to_rtc_device(dev);
+
+	if (!candidate->ops->set_alarm)
+		return 0;
+	if (!device_may_wakeup(candidate->dev.parent))
+		return 0;
+
+	*(char **)name_ptr = dev->bus_id;
+	return 1;
+}
+
+/*
+ * Kernel options like "test_suspend=mem" force suspend/resume sanity tests
+ * at startup time.  They're normally disabled, for faster boot and because
+ * we can't know which states really work on this particular system.
+ */
+static suspend_state_t test_state __initdata = PM_SUSPEND_ON;
+
+static char warn_bad_state[] __initdata =
+	KERN_WARNING "PM: can't test '%s' suspend state\n";
+
+static int __init setup_test_suspend(char *value)
+{

kernel/power/main.c +27 -0

+	struct rtc_device	*rtc = NULL;
+
+	/* PM is initialized by now; is that state testable? */
+	if (test_state == PM_SUSPEND_ON)
+		goto done;
+	if (!valid_state(test_state)) {
+		printk(warn_bad_state, pm_states[test_state]);
+		goto done;
+	}
+
+	/* RTCs have initialized by now too ... can we use one? */
+	class_find_device(rtc_class, &pony, has_wakealarm);
+	if (pony)
+		rtc = rtc_class_open(pony);
+	if (!rtc) {
+		printk(warn_no_rtc);
+		goto done;
+	}
+
+	/* go for it */
+	test_wakealarm(rtc, test_state);
+	rtc_class_close(rtc);
+done:
+	return 0;
+}
+late_initcall(test_suspend);
+

kernel/power/main.c static inline int suspend_test(int level · line 166

Quoted 1 line

kernel/power/main.c +1 -0

+	WARN_ON_ONCE(msec > (TEST_SUSPEND_SECONDS * 1000));

We should have a comment here explaining what we're warning about. Why would it take more that five seconds?

Better might be to just add a nice printk - I don't think we need the stack trace here.

kernel/power/main.c static inline int suspend_test(int level · line 166

Quoted 1 line

kernel/power/main.c +1 -0

+	WARN_ON_ONCE(msec > (TEST_SUSPEND_SECONDS * 1000));

We should have a comment here explaining what we're warning about. Why would it take more that five seconds?

Better might be to just add a nice printk - I don't think we need the stack trace here.

Quoted 4 lines · Andrew Morton

kernel/power/main.c static inline int suspend_test(int level · line 166

Quoted 1 line

kernel/power/main.c +1 -0

+	WARN_ON_ONCE(msec > (TEST_SUSPEND_SECONDS * 1000));

We should have a comment here explaining what we're warning about. Why would it take more that five seconds?

i asked for that because we had regressions in the past in the form of "it takes one minute to resume".

[As gcc seems unable to help us out selecting the appropriate data segment for the code, how about we did something like this?]

When using printk from __init functions it would be desirable to place the printk format strings in __initdata. Add a printk_init() variant which does this.

[As gcc seems unable to help us out selecting the appropriate data segment for the code, how about we did something like this?]

When using printk from __init functions it would be desirable to place the printk format strings in __initdata. Add a printk_init() variant which does this.

[As gcc seems unable to help us out selecting the appropriate data segment for the code, how about we did something like this?]

When using printk from __init functions it would be desirable to place the printk format strings in __initdata. Add a printk_init() variant which does this.

This printk_init() is necessarily a #define so that we can declare the format string in static scope and mark it __initdata. We then call a newly introduced __printk_init() variant which is identicle to printk() but marked __init itself. By ensuring that an __init variant of printk is used we get proper section violation warnings when this is used incorrectly:

WARNING: vmlinux.o(.text+0x3): Section mismatch in reference from the
function something() to the variable .init.data:__printk_init_fmt.31426
The function something() references
the variable __initdata __printk_init_fmt.31426.
This is often because something lacks a __initdata
annotation or the annotation of __printk_init_fmt.31426 is wrong.

Note I have followed printk's pattern for __cold annotations.

---
 include/linux/kernel.h |   10 ++++++++++
 kernel/printk.c        |   12 ++++++++++++
 2 files changed, 22 insertions(+), 0 deletions(-)

include/linux/kernel.h +10 -0

index 792bf0a..7754196 100644
@@ -180,6 +180,13 @@ struct pid;
 extern struct pid *session_of_pgrp(struct pid *pgrp);
 
 #ifdef CONFIG_PRINTK
+#define printk_init(fmt, args...) \
+do { \
+        static char __printk_init_fmt[] __initdata = fmt; \
+        __printk_init(__printk_init_fmt, ##args); \
+} while (0)
+asmlinkage int __printk_init(const char * fmt, ...)
+	__attribute__ ((format (printf, 1, 2))) __cold;
 asmlinkage int vprintk(const char *fmt, va_list args)
 	__attribute__ ((format (printf, 1, 0)));
 asmlinkage int printk(const char * fmt, ...)

@@ -196,6 +203,9 @@ extern int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst);
 extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
 				   unsigned int interval_msec);
 #else
+asmlinkage int printk_init(const char * fmt, ...)
+	__attribute__ ((format (printf, 1, 2))) __cold;
+static inline int __cold printk_init(const char *s, ...) { return 0; }
 static inline int vprintk(const char *s, va_list args)
 	__attribute__ ((format (printf, 1, 0)));
 static inline int vprintk(const char *s, va_list args) { return 0; }

kernel/printk.c +1 -0

index 8fb01c3..992a5c0 100644
@@ -616,6 +616,18 @@ asmlinkage int printk(const char *fmt, ...)
 	return r;
 }
 
+asmlinkage __init int __printk_init(const char *fmt, ...)

[As gcc seems unable to help us out selecting the appropriate data segment for the code, how about we did something like this?]

When using printk from __init functions it would be desirable to place the printk format strings in __initdata. Add a printk_init() variant which does this.

This printk_init() is necessarily a #define so that we can declare the format string in static scope and mark it __initdata. We then call a newly introduced __printk_init() variant which is identicle to printk() but marked __init itself. By ensuring that an __init variant of printk is used we get proper section violation warnings when this is used incorrectly:

WARNING: vmlinux.o(.text+0x3): Section mismatch in reference from the
function something() to the variable .init.data:__printk_init_fmt.31426
The function something() references
the variable __initdata __printk_init_fmt.31426.
This is often because something lacks a __initdata
annotation or the annotation of __printk_init_fmt.31426 is wrong.

Note I have followed printk's pattern for __cold annotations.

---
 include/linux/kernel.h |   10 ++++++++++
 kernel/printk.c        |   12 ++++++++++++
 2 files changed, 22 insertions(+), 0 deletions(-)

include/linux/kernel.h +10 -0

index 792bf0a..7754196 100644
@@ -180,6 +180,13 @@ struct pid;
 extern struct pid *session_of_pgrp(struct pid *pgrp);
 
 #ifdef CONFIG_PRINTK
+#define printk_init(fmt, args...) \
+do { \
+        static char __printk_init_fmt[] __initdata = fmt; \
+        __printk_init(__printk_init_fmt, ##args); \
+} while (0)
+asmlinkage int __printk_init(const char * fmt, ...)
+	__attribute__ ((format (printf, 1, 2))) __cold;
 asmlinkage int vprintk(const char *fmt, va_list args)
 	__attribute__ ((format (printf, 1, 0)));
 asmlinkage int printk(const char * fmt, ...)

@@ -196,6 +203,9 @@ extern int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst);
 extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
 				   unsigned int interval_msec);
 #else
+asmlinkage int printk_init(const char * fmt, ...)
+	__attribute__ ((format (printf, 1, 2))) __cold;
+static inline int __cold printk_init(const char *s, ...) { return 0; }
 static inline int vprintk(const char *s, va_list args)
 	__attribute__ ((format (printf, 1, 0)));
 static inline int vprintk(const char *s, va_list args) { return 0; }

kernel/printk.c +1 -0

index 8fb01c3..992a5c0 100644
@@ -616,6 +616,18 @@ asmlinkage int printk(const char *fmt, ...)
 	return r;
 }
 
+asmlinkage __init int __printk_init(const char *fmt, ...)

Quoted 14 lines · On Tue, 3 Jun 2008 10:27:32 +0100 Andy Whitcroft <[email protected]> wrote:

[As gcc seems unable to help us out selecting the appropriate data segment for the code, how about we did something like this?]

When using printk from __init functions it would be desirable to place the printk format strings in __initdata. Add a printk_init() variant which does this.

This printk_init() is necessarily a #define so that we can declare the format string in static scope and mark it __initdata. We then call a newly introduced __printk_init() variant which is identicle to printk() but marked __init itself. By ensuring that an __init variant of printk is used we get proper section violation warnings when this is used incorrectly:

Quoted 9 lines

WARNING: vmlinux.o(.text+0x3): Section mismatch in reference from the
function something() to the variable .init.data:__printk_init_fmt.31426
The function something() references
the variable __initdata __printk_init_fmt.31426.
This is often because something lacks a __initdata
annotation or the annotation of __printk_init_fmt.31426 is wrong.

Note I have followed printk's pattern for __cold annotations.

Ho hum. This give everyone another way in which to bury everyone else with patches.

Wouldn't it be great if checkpatch were to detect
fail-to-use-printk_init() in an __init function?

oh, speaking of checkpatch: please use it :)

Quoted 41 lines

---
 include/linux/kernel.h |   10 ++++++++++
 kernel/printk.c        |   12 ++++++++++++
 2 files changed, 22 insertions(+), 0 deletions(-)

include/linux/kernel.h +10 -0

index 792bf0a..7754196 100644
@@ -180,6 +180,13 @@ struct pid;
 extern struct pid *session_of_pgrp(struct pid *pgrp);
 
 #ifdef CONFIG_PRINTK
+#define printk_init(fmt, args...) \
+do { \
+        static char __printk_init_fmt[] __initdata = fmt; \
+        __printk_init(__printk_init_fmt, ##args); \
+} while (0)
+asmlinkage int __printk_init(const char * fmt, ...)
+     __attribute__ ((format (printf, 1, 2))) __cold;
 asmlinkage int vprintk(const char *fmt, va_list args)
      __attribute__ ((format (printf, 1, 0)));
 asmlinkage int printk(const char * fmt, ...)

@@ -196,6 +203,9 @@ extern int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst);
 extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
                                 unsigned int interval_msec);
 #else
+asmlinkage int printk_init(const char * fmt, ...)
+     __attribute__ ((format (printf, 1, 2))) __cold;
+static inline int __cold printk_init(const char *s, ...) { return 0; }
 static inline int vprintk(const char *s, va_list args)
      __attribute__ ((format (printf, 1, 0)));
 static inline int vprintk(const char *s, va_list args) { return 0; }

kernel/printk.c +1 -0

index 8fb01c3..992a5c0 100644
@@ -616,6 +616,18 @@ asmlinkage int printk(const char *fmt, ...)
      return r;
 }
 
+asmlinkage __init int __printk_init(const char *fmt, ...)

kernel/printk.c asmlinkage int printk(const char *fmt, ...) · line 629

Quoted 10 lines

kernel/printk.c +10 -0

+{
+     va_list args;
+     int r;
+
+     va_start(args, fmt);
+     r = vprintk(fmt, args);
+     va_end(args);
+
+     return r;
+}

We're going to want to be able to call printk_init() from modules. Please fix and test that, if we decide to proceed.

Oh, and we're going to need printk_meminit() and printk_cpuinit() and whatever.

Which probably means that __printk_init() can't be __init, unless all the CONFIG_ settings which control __cpuinit, __meminit etc are blowing in the right direction.

It would be good if we could get some idea of the savings here, because boy this is going to be a pain.

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To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected]
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Please read the FAQ at http://www.tux.org/lkml/

Quoted 14 lines · On Tue, 3 Jun 2008 10:27:32 +0100 Andy Whitcroft <[email protected]> wrote:

[As gcc seems unable to help us out selecting the appropriate data segment for the code, how about we did something like this?]

When using printk from __init functions it would be desirable to place the printk format strings in __initdata. Add a printk_init() variant which does this.

This printk_init() is necessarily a #define so that we can declare the format string in static scope and mark it __initdata. We then call a newly introduced __printk_init() variant which is identicle to printk() but marked __init itself. By ensuring that an __init variant of printk is used we get proper section violation warnings when this is used incorrectly:

Quoted 9 lines

WARNING: vmlinux.o(.text+0x3): Section mismatch in reference from the
function something() to the variable .init.data:__printk_init_fmt.31426
The function something() references
the variable __initdata __printk_init_fmt.31426.
This is often because something lacks a __initdata
annotation or the annotation of __printk_init_fmt.31426 is wrong.

Note I have followed printk's pattern for __cold annotations.

Ho hum. This give everyone another way in which to bury everyone else with patches.

Wouldn't it be great if checkpatch were to detect
fail-to-use-printk_init() in an __init function?

oh, speaking of checkpatch: please use it :)

Quoted 41 lines

---
 include/linux/kernel.h |   10 ++++++++++
 kernel/printk.c        |   12 ++++++++++++
 2 files changed, 22 insertions(+), 0 deletions(-)

include/linux/kernel.h +10 -0

index 792bf0a..7754196 100644
@@ -180,6 +180,13 @@ struct pid;
 extern struct pid *session_of_pgrp(struct pid *pgrp);
 
 #ifdef CONFIG_PRINTK
+#define printk_init(fmt, args...) \
+do { \
+        static char __printk_init_fmt[] __initdata = fmt; \
+        __printk_init(__printk_init_fmt, ##args); \
+} while (0)
+asmlinkage int __printk_init(const char * fmt, ...)
+     __attribute__ ((format (printf, 1, 2))) __cold;
 asmlinkage int vprintk(const char *fmt, va_list args)
      __attribute__ ((format (printf, 1, 0)));
 asmlinkage int printk(const char * fmt, ...)

@@ -196,6 +203,9 @@ extern int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst);
 extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
                                 unsigned int interval_msec);
 #else
+asmlinkage int printk_init(const char * fmt, ...)
+     __attribute__ ((format (printf, 1, 2))) __cold;
+static inline int __cold printk_init(const char *s, ...) { return 0; }
 static inline int vprintk(const char *s, va_list args)
      __attribute__ ((format (printf, 1, 0)));
 static inline int vprintk(const char *s, va_list args) { return 0; }

kernel/printk.c +1 -0

index 8fb01c3..992a5c0 100644
@@ -616,6 +616,18 @@ asmlinkage int printk(const char *fmt, ...)
      return r;
 }
 
+asmlinkage __init int __printk_init(const char *fmt, ...)

kernel/printk.c asmlinkage int printk(const char *fmt, ...) · line 629

Quoted 10 lines

kernel/printk.c +10 -0

+{
+     va_list args;
+     int r;
+
+     va_start(args, fmt);
+     r = vprintk(fmt, args);
+     va_end(args);
+
+     return r;
+}

We're going to want to be able to call printk_init() from modules. Please fix and test that, if we decide to proceed.

Oh, and we're going to need printk_meminit() and printk_cpuinit() and whatever.

Which probably means that __printk_init() can't be __init, unless all the CONFIG_ settings which control __cpuinit, __meminit etc are blowing in the right direction.

It would be good if we could get some idea of the savings here, because boy this is going to be a pain.

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

We're going to want to be able to call printk_init() from modules. Please fix and test that, if we decide to proceed.

We're going to want to be able to call printk_init() from modules. Please fix and test that, if we decide to proceed.

Quoted 2 lines · Andrew Morton

We're going to want to be able to call printk_init() from modules. Please fix and test that, if we decide to proceed.

Can we fix that by making it an alias for printk in the module case?

The only reason we need it to be __init is so that we get the section warnings when you use it from non-init code, right? Won't we get the warning when non-init code refers to the string in initdata anyway?

WARNING: vmlinux.o(.text+0x3): Section mismatch in reference from the
function something() to the variable .init.data:__printk_init_fmt.31426
The function something() references
the variable __initdata __printk_init_fmt.31426.
This is often because something lacks a __initdata
annotation or the annotation of __printk_init_fmt.31426 is wrong.

Quoted 2 lines · Andrew Morton

We're going to want to be able to call printk_init() from modules. Please fix and test that, if we decide to proceed.

Can we fix that by making it an alias for printk in the module case?

The only reason we need it to be __init is so that we get the section warnings when you use it from non-init code, right? Won't we get the warning when non-init code refers to the string in initdata anyway?

WARNING: vmlinux.o(.text+0x3): Section mismatch in reference from the
function something() to the variable .init.data:__printk_init_fmt.31426
The function something() references
the variable __initdata __printk_init_fmt.31426.
This is often because something lacks a __initdata
annotation or the annotation of __printk_init_fmt.31426 is wrong.

Quoted 4 lines · David Woodhouse

Quoted 2 lines · Andrew Morton

We're going to want to be able to call printk_init() from modules. Please fix and test that, if we decide to proceed.

Quoted 5 lines

Can we fix that by making it an alias for printk in the module case?

The only reason we need it to be __init is so that we get the section warnings when you use it from non-init code, right? Won't we get the warning when non-init code refers to the string in initdata anyway?

In fact, wasn't the warning Andy showed such a warning?

Quoted 4 lines · David Woodhouse

Quoted 2 lines · Andrew Morton

We're going to want to be able to call printk_init() from modules. Please fix and test that, if we decide to proceed.

Quoted 5 lines

Can we fix that by making it an alias for printk in the module case?

The only reason we need it to be __init is so that we get the section warnings when you use it from non-init code, right? Won't we get the warning when non-init code refers to the string in initdata anyway?

In fact, wasn't the warning Andy showed such a warning?

Quoted 7 lines · Johannes Berg

Quoted 6 lines · David Woodhouse

Quoted 2 lines · Andrew Morton

We're going to want to be able to call printk_init() from modules. Please fix and test that, if we decide to proceed.

Can we fix that by making it an alias for printk in the module case?

Quoted 5 lines

Quoted 3 lines

The only reason we need it to be __init is so that we get the section warnings when you use it from non-init code, right? Won't we get the warning when non-init code refers to the string in initdata anyway?

In fact, wasn't the warning Andy showed such a warning?

Hm, yes it was. Why do we need __printk_init() to be anything other than an alias for printk, then?

Quoted 7 lines · Johannes Berg

Quoted 6 lines · David Woodhouse

Quoted 2 lines · Andrew Morton

We're going to want to be able to call printk_init() from modules. Please fix and test that, if we decide to proceed.

Can we fix that by making it an alias for printk in the module case?

Quoted 5 lines

Quoted 3 lines

The only reason we need it to be __init is so that we get the section warnings when you use it from non-init code, right? Won't we get the warning when non-init code refers to the string in initdata anyway?

In fact, wasn't the warning Andy showed such a warning?

Hm, yes it was. Why do we need __printk_init() to be anything other than an alias for printk, then?

Quoted 3 lines

When using printk from __init functions it would be desirable to place the printk format strings in __initdata. Add a printk_init() variant which does this.

Wouldn't it be great if checkpatch were to detect
fail-to-use-printk_init() in an __init function?

Quoted 3 lines

When using printk from __init functions it would be desirable to place the printk format strings in __initdata. Add a printk_init() variant which does this.

Wouldn't it be great if checkpatch were to detect
fail-to-use-printk_init() in an __init function?

kernel/power/main.c static int __init pm_init(void) · line 589

Quoted 10 lines

kernel/power/main.c +10 -0

+static void __init test_wakealarm(struct rtc_device *rtc, suspend_state_t state)
+{
+	static char		err_readtime [] __initdata =
+		KERN_ERR "PM: can't read %s time, err %d\n";
+	static char		err_wakealarm [] __initdata =
+		KERN_ERR "PM: can't set %s wakealarm, err %d\n";
+	static char		err_suspend [] __initdata =
+		KERN_ERR "PM: suspend test failed, error %d\n";
+	static char		info_test [] __initdata =
+		KERN_INFO "PM: test RTC wakeup from '%s' suspend\n";

- One tab before the variable space is a waste of space. Two tabs is just extravagant.

- The space before the [] shouldn't be there. checkpatch misses this.

kernel/power/main.c static int __init pm_init(void) · line 589

Quoted 10 lines

kernel/power/main.c +10 -0

+static void __init test_wakealarm(struct rtc_device *rtc, suspend_state_t state)
+{
+	static char		err_readtime [] __initdata =
+		KERN_ERR "PM: can't read %s time, err %d\n";
+	static char		err_wakealarm [] __initdata =
+		KERN_ERR "PM: can't set %s wakealarm, err %d\n";
+	static char		err_suspend [] __initdata =
+		KERN_ERR "PM: suspend test failed, error %d\n";
+	static char		info_test [] __initdata =
+		KERN_INFO "PM: test RTC wakeup from '%s' suspend\n";

- One tab before the variable space is a waste of space. Two tabs is just extravagant.

- The space before the [] shouldn't be there. checkpatch misses this.

Boot-time test for system suspend states (STR or standby). The generic RTC framework triggers wakeup alarms, which are used to exit those states.

- Measures some aspects of suspend time ... this uses "jiffies" until someone converts it to use a timebase that works properly even while timer IRQs are disabled.

- Triggered by a command line parameter. By default nothing even vaguely troublesome will happen, but "test_suspend=mem" will give you a brief STR test during system boot. (Or you may need to use "test_suspend=standby" instead, if your hardware needs that.)

This isn't without problems. It fires early enough during boot that for example both PCMCIA and MMC stacks have misbehaved. The workaround in those cases was to boot without such media cards inserted.

Boot-time test for system suspend states (STR or standby). The generic RTC framework triggers wakeup alarms, which are used to exit those states.

- Measures some aspects of suspend time ... this uses "jiffies" until someone converts it to use a timebase that works properly even while timer IRQs are disabled.

- Triggered by a command line parameter. By default nothing even vaguely troublesome will happen, but "test_suspend=mem" will give you a brief STR test during system boot. (Or you may need to use "test_suspend=standby" instead, if your hardware needs that.)

This isn't without problems. It fires early enough during boot that for example both PCMCIA and MMC stacks have misbehaved. The workaround in those cases was to boot without such media cards inserted.