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1 | What: /sys/power/ |
2 | Date: August 2006 | |
49db1903 | 3 | Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
84ed64ee RW |
4 | Description: |
5 | The /sys/power directory will contain files that will | |
6 | provide a unified interface to the power management | |
7 | subsystem. | |
8 | ||
9 | What: /sys/power/state | |
10 | Date: August 2006 | |
49db1903 | 11 | Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
84ed64ee RW |
12 | Description: |
13 | The /sys/power/state file controls the system power state. | |
14 | Reading from this file returns what states are supported, | |
af02b5fd GU |
15 | which is hard-coded to 'freeze' (Low-Power Idle), 'standby' |
16 | (Power-On Suspend), 'mem' (Suspend-to-RAM), and 'disk' | |
17 | (Suspend-to-Disk). | |
84ed64ee RW |
18 | |
19 | Writing to this file one of these strings causes the system to | |
20 | transition into that state. Please see the file | |
21 | Documentation/power/states.txt for a description of each of | |
22 | these states. | |
23 | ||
24 | What: /sys/power/disk | |
b918f6e6 | 25 | Date: September 2006 |
49db1903 | 26 | Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
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27 | Description: |
28 | The /sys/power/disk file controls the operating mode of the | |
29 | suspend-to-disk mechanism. Reading from this file returns | |
30 | the name of the method by which the system will be put to | |
31 | sleep on the next suspend. There are four methods supported: | |
32 | 'firmware' - means that the memory image will be saved to disk | |
33 | by some firmware, in which case we also assume that the | |
34 | firmware will handle the system suspend. | |
35 | 'platform' - the memory image will be saved by the kernel and | |
36 | the system will be put to sleep by the platform driver (e.g. | |
37 | ACPI or other PM registers). | |
38 | 'shutdown' - the memory image will be saved by the kernel and | |
39 | the system will be powered off. | |
40 | 'reboot' - the memory image will be saved by the kernel and | |
41 | the system will be rebooted. | |
42 | ||
b918f6e6 RW |
43 | Additionally, /sys/power/disk can be used to turn on one of the |
44 | two testing modes of the suspend-to-disk mechanism: 'testproc' | |
45 | or 'test'. If the suspend-to-disk mechanism is in the | |
46 | 'testproc' mode, writing 'disk' to /sys/power/state will cause | |
47 | the kernel to disable nonboot CPUs and freeze tasks, wait for 5 | |
48 | seconds, unfreeze tasks and enable nonboot CPUs. If it is in | |
49 | the 'test' mode, writing 'disk' to /sys/power/state will cause | |
50 | the kernel to disable nonboot CPUs and freeze tasks, shrink | |
51 | memory, suspend devices, wait for 5 seconds, resume devices, | |
52 | unfreeze tasks and enable nonboot CPUs. Then, we are able to | |
53 | look in the log messages and work out, for example, which code | |
54 | is being slow and which device drivers are misbehaving. | |
55 | ||
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56 | The suspend-to-disk method may be chosen by writing to this |
57 | file one of the accepted strings: | |
58 | ||
59 | 'firmware' | |
60 | 'platform' | |
61 | 'shutdown' | |
62 | 'reboot' | |
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63 | 'testproc' |
64 | 'test' | |
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65 | |
66 | It will only change to 'firmware' or 'platform' if the system | |
67 | supports that. | |
68 | ||
69 | What: /sys/power/image_size | |
70 | Date: August 2006 | |
49db1903 | 71 | Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
84ed64ee RW |
72 | Description: |
73 | The /sys/power/image_size file controls the size of the image | |
74 | created by the suspend-to-disk mechanism. It can be written a | |
75 | string representing a non-negative integer that will be used | |
76 | as an upper limit of the image size, in bytes. The kernel's | |
77 | suspend-to-disk code will do its best to ensure the image size | |
78 | will not exceed this number. However, if it turns out to be | |
79 | impossible, the kernel will try to suspend anyway using the | |
80 | smallest image possible. In particular, if "0" is written to | |
81 | this file, the suspend image will be as small as possible. | |
82 | ||
83 | Reading from this file will display the current image size | |
84 | limit, which is set to 500 MB by default. | |
85 | ||
86 | What: /sys/power/pm_trace | |
87 | Date: August 2006 | |
49db1903 | 88 | Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
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89 | Description: |
90 | The /sys/power/pm_trace file controls the code which saves the | |
91 | last PM event point in the RTC across reboots, so that you can | |
92 | debug a machine that just hangs during suspend (or more | |
93 | commonly, during resume). Namely, the RTC is only used to save | |
94 | the last PM event point if this file contains '1'. Initially | |
95 | it contains '0' which may be changed to '1' by writing a | |
96 | string representing a nonzero integer into it. | |
97 | ||
98 | To use this debugging feature you should attempt to suspend | |
99 | the machine, then reboot it and run | |
100 | ||
101 | dmesg -s 1000000 | grep 'hash matches' | |
102 | ||
d33ac60b JH |
103 | If you do not get any matches (or they appear to be false |
104 | positives), it is possible that the last PM event point | |
105 | referred to a device created by a loadable kernel module. In | |
106 | this case cat /sys/power/pm_trace_dev_match (see below) after | |
107 | your system is started up and the kernel modules are loaded. | |
108 | ||
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109 | CAUTION: Using it will cause your machine's real-time (CMOS) |
110 | clock to be set to a random invalid time after a resume. | |
0e06b4a8 | 111 | |
d33ac60b JH |
112 | What; /sys/power/pm_trace_dev_match |
113 | Date: October 2010 | |
114 | Contact: James Hogan <james@albanarts.com> | |
115 | Description: | |
116 | The /sys/power/pm_trace_dev_match file contains the name of the | |
117 | device associated with the last PM event point saved in the RTC | |
118 | across reboots when pm_trace has been used. More precisely it | |
119 | contains the list of current devices (including those | |
120 | registered by loadable kernel modules since boot) which match | |
121 | the device hash in the RTC at boot, with a newline after each | |
122 | one. | |
123 | ||
124 | The advantage of this file over the hash matches printed to the | |
125 | kernel log (see /sys/power/pm_trace), is that it includes | |
126 | devices created after boot by loadable kernel modules. | |
127 | ||
128 | Due to the small hash size necessary to fit in the RTC, it is | |
129 | possible that more than one device matches the hash, in which | |
130 | case further investigation is required to determine which | |
131 | device is causing the problem. Note that genuine RTC clock | |
132 | values (such as when pm_trace has not been used), can still | |
133 | match a device and output it's name here. | |
134 | ||
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135 | What: /sys/power/pm_async |
136 | Date: January 2009 | |
49db1903 | 137 | Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
0e06b4a8 RW |
138 | Description: |
139 | The /sys/power/pm_async file controls the switch allowing the | |
140 | user space to enable or disable asynchronous suspend and resume | |
141 | of devices. If enabled, this feature will cause some device | |
142 | drivers' suspend and resume callbacks to be executed in parallel | |
143 | with each other and with the main suspend thread. It is enabled | |
144 | if this file contains "1", which is the default. It may be | |
145 | disabled by writing "0" to this file, in which case all devices | |
146 | will be suspended and resumed synchronously. | |
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147 | |
148 | What: /sys/power/wakeup_count | |
149 | Date: July 2010 | |
49db1903 | 150 | Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
c125e96f RW |
151 | Description: |
152 | The /sys/power/wakeup_count file allows user space to put the | |
153 | system into a sleep state while taking into account the | |
154 | concurrent arrival of wakeup events. Reading from it returns | |
155 | the current number of registered wakeup events and it blocks if | |
156 | some wakeup events are being processed at the time the file is | |
157 | read from. Writing to it will only succeed if the current | |
158 | number of wakeup events is equal to the written value and, if | |
159 | successful, will make the kernel abort a subsequent transition | |
160 | to a sleep state if any wakeup events are reported after the | |
161 | write has returned. | |
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162 | |
163 | What: /sys/power/reserved_size | |
164 | Date: May 2011 | |
49db1903 | 165 | Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
ddeb6487 RW |
166 | Description: |
167 | The /sys/power/reserved_size file allows user space to control | |
168 | the amount of memory reserved for allocations made by device | |
169 | drivers during the "device freeze" stage of hibernation. It can | |
170 | be written a string representing a non-negative integer that | |
171 | will be used as the amount of memory to reserve for allocations | |
172 | made by device drivers' "freeze" callbacks, in bytes. | |
173 | ||
174 | Reading from this file will display the current value, which is | |
175 | set to 1 MB by default. | |
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176 | |
177 | What: /sys/power/autosleep | |
178 | Date: April 2012 | |
49db1903 | 179 | Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
7483b4a4 RW |
180 | Description: |
181 | The /sys/power/autosleep file can be written one of the strings | |
182 | returned by reads from /sys/power/state. If that happens, a | |
183 | work item attempting to trigger a transition of the system to | |
184 | the sleep state represented by that string is queued up. This | |
185 | attempt will only succeed if there are no active wakeup sources | |
186 | in the system at that time. After every execution, regardless | |
187 | of whether or not the attempt to put the system to sleep has | |
188 | succeeded, the work item requeues itself until user space | |
189 | writes "off" to /sys/power/autosleep. | |
190 | ||
191 | Reading from this file causes the last string successfully | |
192 | written to it to be returned. | |
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193 | |
194 | What: /sys/power/wake_lock | |
195 | Date: February 2012 | |
49db1903 | 196 | Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
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197 | Description: |
198 | The /sys/power/wake_lock file allows user space to create | |
199 | wakeup source objects and activate them on demand (if one of | |
200 | those wakeup sources is active, reads from the | |
201 | /sys/power/wakeup_count file block or return false). When a | |
202 | string without white space is written to /sys/power/wake_lock, | |
203 | it will be assumed to represent a wakeup source name. If there | |
204 | is a wakeup source object with that name, it will be activated | |
205 | (unless active already). Otherwise, a new wakeup source object | |
206 | will be registered, assigned the given name and activated. | |
207 | If a string written to /sys/power/wake_lock contains white | |
208 | space, the part of the string preceding the white space will be | |
209 | regarded as a wakeup source name and handled as descrived above. | |
210 | The other part of the string will be regarded as a timeout (in | |
211 | nanoseconds) such that the wakeup source will be automatically | |
212 | deactivated after it has expired. The timeout, if present, is | |
213 | set regardless of the current state of the wakeup source object | |
214 | in question. | |
215 | ||
216 | Reads from this file return a string consisting of the names of | |
217 | wakeup sources created with the help of it that are active at | |
218 | the moment, separated with spaces. | |
219 | ||
220 | ||
221 | What: /sys/power/wake_unlock | |
222 | Date: February 2012 | |
49db1903 | 223 | Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
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224 | Description: |
225 | The /sys/power/wake_unlock file allows user space to deactivate | |
226 | wakeup sources created with the help of /sys/power/wake_lock. | |
227 | When a string is written to /sys/power/wake_unlock, it will be | |
228 | assumed to represent the name of a wakeup source to deactivate. | |
229 | If a wakeup source object of that name exists and is active at | |
230 | the moment, it will be deactivated. | |
231 | ||
232 | Reads from this file return a string consisting of the names of | |
233 | wakeup sources created with the help of /sys/power/wake_lock | |
234 | that are inactive at the moment, separated with spaces. | |
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235 | |
236 | What: /sys/power/pm_print_times | |
237 | Date: May 2012 | |
238 | Contact: Sameer Nanda <snanda@chromium.org> | |
239 | Description: | |
240 | The /sys/power/pm_print_times file allows user space to | |
241 | control whether the time taken by devices to suspend and | |
242 | resume is printed. These prints are useful for hunting down | |
243 | devices that take too long to suspend or resume. | |
244 | ||
245 | Writing a "1" enables this printing while writing a "0" | |
246 | disables it. The default value is "0". Reading from this file | |
247 | will display the current value. |