PM: Add sysfs attr for rechecking dev hash from PM trace (d33ac60b) · Commits · 戴 / test

Documentation/ABI/testing/sysfs-power

+29 −0

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		@@ -99,9 +99,38 @@ Description:

		dmesg -s 1000000 \| grep 'hash matches'

		If you do not get any matches (or they appear to be false
		positives), it is possible that the last PM event point
		referred to a device created by a loadable kernel module. In
		this case cat /sys/power/pm_trace_dev_match (see below) after
		your system is started up and the kernel modules are loaded.

		CAUTION: Using it will cause your machine's real-time (CMOS)
		clock to be set to a random invalid time after a resume.

		What; /sys/power/pm_trace_dev_match
		Date: October 2010
		Contact: James Hogan <james@albanarts.com>
		Description:
		The /sys/power/pm_trace_dev_match file contains the name of the
		device associated with the last PM event point saved in the RTC
		across reboots when pm_trace has been used. More precisely it
		contains the list of current devices (including those
		registered by loadable kernel modules since boot) which match
		the device hash in the RTC at boot, with a newline after each
		one.

		The advantage of this file over the hash matches printed to the
		kernel log (see /sys/power/pm_trace), is that it includes
		devices created after boot by loadable kernel modules.

		Due to the small hash size necessary to fit in the RTC, it is
		possible that more than one device matches the hash, in which
		case further investigation is required to determine which
		device is causing the problem. Note that genuine RTC clock
		values (such as when pm_trace has not been used), can still
		match a device and output it's name here.

		What: /sys/power/pm_async
		Date: January 2009
		Contact: Rafael J. Wysocki <rjw@sisk.pl>

Documentation/power/s2ram.txt

+7 −0

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		@@ -49,6 +49,13 @@ machine that doesn't boot) is:
		device (lspci and /sys/devices/pci* is your friend), and see if you can
		fix it, disable it, or trace into its resume function.

		If no device matches the hash (or any matches appear to be false positives),
		the culprit may be a device from a loadable kernel module that is not loaded
		until after the hash is checked. You can check the hash against the current
		devices again after more modules are loaded using sysfs:

		cat /sys/power/pm_trace_dev_match

		For example, the above happens to be the VGA device on my EVO, which I
		used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out
		that "radeonfb" simply cannot resume that device - it tries to set the

drivers/base/power/trace.c

+31 −0

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		@@ -207,6 +207,37 @@ static int show_dev_hash(unsigned int value)

		static unsigned int hash_value_early_read;

		int show_trace_dev_match(char *buf, size_t size)
		{
		unsigned int value = hash_value_early_read / (USERHASH * FILEHASH);
		int ret = 0;
		struct list_head *entry;

		/*
		* It's possible that multiple devices will match the hash and we can't
		* tell which is the culprit, so it's best to output them all.
		*/
		device_pm_lock();
		entry = dpm_list.prev;
		while (size && entry != &dpm_list) {
		struct device *dev = to_device(entry);
		unsigned int hash = hash_string(DEVSEED, dev_name(dev),
		DEVHASH);
		if (hash == value) {
		int len = snprintf(buf, size, "%s\n",
		dev_driver_string(dev));
		if (len > size)
		len = size;
		buf += len;
		ret += len;
		size -= len;
		}
		entry = entry->prev;
		}
		device_pm_unlock();
		return ret;
		}

		static int early_resume_init(void)
		{
		hash_value_early_read = read_magic_time();

include/linux/resume-trace.h

+2 −0

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		@@ -3,6 +3,7 @@

		#ifdef CONFIG_PM_TRACE
		#include <asm/resume-trace.h>
		#include <linux/types.h>

		extern int pm_trace_enabled;

		@@ -14,6 +15,7 @@ static inline int pm_trace_is_enabled(void)
		struct device;
		extern void set_trace_device(struct device *);
		extern void generate_resume_trace(const void *tracedata, unsigned int user);
		extern int show_trace_dev_match(char *buf, size_t size);

		#define TRACE_DEVICE(dev) do { \
		if (pm_trace_enabled) \

kernel/power/main.c

+18 −0

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		@@ -281,12 +281,30 @@ pm_trace_store(struct kobject kobj, struct kobj_attribute attr,
		}

		power_attr(pm_trace);

		static ssize_t pm_trace_dev_match_show(struct kobject *kobj,
		struct kobj_attribute *attr,
		char *buf)
		{
		return show_trace_dev_match(buf, PAGE_SIZE);
		}

		static ssize_t
		pm_trace_dev_match_store(struct kobject kobj, struct kobj_attribute attr,
		const char *buf, size_t n)
		{
		return -EINVAL;
		}

		power_attr(pm_trace_dev_match);

		#endif /* CONFIG_PM_TRACE */

		static struct attribute * g[] = {
		&state_attr.attr,
		#ifdef CONFIG_PM_TRACE
		&pm_trace_attr.attr,
		&pm_trace_dev_match_attr.attr,
		#endif
		#ifdef CONFIG_PM_SLEEP
		&pm_async_attr.attr,

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