1What: /sys/power/ 2Date: August 2006 3Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 4Description: 5 The /sys/power directory will contain files that will 6 provide a unified interface to the power management 7 subsystem. 8 9What: /sys/power/state 10Date: November 2016 11Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 12Description: 13 The /sys/power/state file controls system sleep states. 14 Reading from this file returns the available sleep state 15 labels, which may be "mem" (suspend), "standby" (power-on 16 suspend), "freeze" (suspend-to-idle) and "disk" (hibernation). 17 18 Writing one of the above strings to this file causes the system 19 to transition into the corresponding state, if available. 20 21 See Documentation/power/states.txt for more information. 22 23What: /sys/power/mem_sleep 24Date: November 2016 25Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 26Description: 27 The /sys/power/mem_sleep file controls the operating mode of 28 system suspend. Reading from it returns the available modes 29 as "s2idle" (always present), "shallow" and "deep" (present if 30 supported). The mode that will be used on subsequent attempts 31 to suspend the system (by writing "mem" to the /sys/power/state 32 file described above) is enclosed in square brackets. 33 34 Writing one of the above strings to this file causes the mode 35 represented by it to be used on subsequent attempts to suspend 36 the system. 37 38 See Documentation/power/states.txt for more information. 39 40What: /sys/power/disk 41Date: September 2006 42Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 43Description: 44 The /sys/power/disk file controls the operating mode of the 45 suspend-to-disk mechanism. Reading from this file returns 46 the name of the method by which the system will be put to 47 sleep on the next suspend. There are four methods supported: 48 'firmware' - means that the memory image will be saved to disk 49 by some firmware, in which case we also assume that the 50 firmware will handle the system suspend. 51 'platform' - the memory image will be saved by the kernel and 52 the system will be put to sleep by the platform driver (e.g. 53 ACPI or other PM registers). 54 'shutdown' - the memory image will be saved by the kernel and 55 the system will be powered off. 56 'reboot' - the memory image will be saved by the kernel and 57 the system will be rebooted. 58 59 Additionally, /sys/power/disk can be used to turn on one of the 60 two testing modes of the suspend-to-disk mechanism: 'testproc' 61 or 'test'. If the suspend-to-disk mechanism is in the 62 'testproc' mode, writing 'disk' to /sys/power/state will cause 63 the kernel to disable nonboot CPUs and freeze tasks, wait for 5 64 seconds, unfreeze tasks and enable nonboot CPUs. If it is in 65 the 'test' mode, writing 'disk' to /sys/power/state will cause 66 the kernel to disable nonboot CPUs and freeze tasks, shrink 67 memory, suspend devices, wait for 5 seconds, resume devices, 68 unfreeze tasks and enable nonboot CPUs. Then, we are able to 69 look in the log messages and work out, for example, which code 70 is being slow and which device drivers are misbehaving. 71 72 The suspend-to-disk method may be chosen by writing to this 73 file one of the accepted strings: 74 75 'firmware' 76 'platform' 77 'shutdown' 78 'reboot' 79 'testproc' 80 'test' 81 82 It will only change to 'firmware' or 'platform' if the system 83 supports that. 84 85What: /sys/power/image_size 86Date: August 2006 87Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 88Description: 89 The /sys/power/image_size file controls the size of the image 90 created by the suspend-to-disk mechanism. It can be written a 91 string representing a non-negative integer that will be used 92 as an upper limit of the image size, in bytes. The kernel's 93 suspend-to-disk code will do its best to ensure the image size 94 will not exceed this number. However, if it turns out to be 95 impossible, the kernel will try to suspend anyway using the 96 smallest image possible. In particular, if "0" is written to 97 this file, the suspend image will be as small as possible. 98 99 Reading from this file will display the current image size 100 limit, which is set to 500 MB by default. 101 102What: /sys/power/pm_trace 103Date: August 2006 104Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 105Description: 106 The /sys/power/pm_trace file controls the code which saves the 107 last PM event point in the RTC across reboots, so that you can 108 debug a machine that just hangs during suspend (or more 109 commonly, during resume). Namely, the RTC is only used to save 110 the last PM event point if this file contains '1'. Initially 111 it contains '0' which may be changed to '1' by writing a 112 string representing a nonzero integer into it. 113 114 To use this debugging feature you should attempt to suspend 115 the machine, then reboot it and run 116 117 dmesg -s 1000000 | grep 'hash matches' 118 119 If you do not get any matches (or they appear to be false 120 positives), it is possible that the last PM event point 121 referred to a device created by a loadable kernel module. In 122 this case cat /sys/power/pm_trace_dev_match (see below) after 123 your system is started up and the kernel modules are loaded. 124 125 CAUTION: Using it will cause your machine's real-time (CMOS) 126 clock to be set to a random invalid time after a resume. 127 128What; /sys/power/pm_trace_dev_match 129Date: October 2010 130Contact: James Hogan <james@albanarts.com> 131Description: 132 The /sys/power/pm_trace_dev_match file contains the name of the 133 device associated with the last PM event point saved in the RTC 134 across reboots when pm_trace has been used. More precisely it 135 contains the list of current devices (including those 136 registered by loadable kernel modules since boot) which match 137 the device hash in the RTC at boot, with a newline after each 138 one. 139 140 The advantage of this file over the hash matches printed to the 141 kernel log (see /sys/power/pm_trace), is that it includes 142 devices created after boot by loadable kernel modules. 143 144 Due to the small hash size necessary to fit in the RTC, it is 145 possible that more than one device matches the hash, in which 146 case further investigation is required to determine which 147 device is causing the problem. Note that genuine RTC clock 148 values (such as when pm_trace has not been used), can still 149 match a device and output it's name here. 150 151What: /sys/power/pm_async 152Date: January 2009 153Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 154Description: 155 The /sys/power/pm_async file controls the switch allowing the 156 user space to enable or disable asynchronous suspend and resume 157 of devices. If enabled, this feature will cause some device 158 drivers' suspend and resume callbacks to be executed in parallel 159 with each other and with the main suspend thread. It is enabled 160 if this file contains "1", which is the default. It may be 161 disabled by writing "0" to this file, in which case all devices 162 will be suspended and resumed synchronously. 163 164What: /sys/power/wakeup_count 165Date: July 2010 166Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 167Description: 168 The /sys/power/wakeup_count file allows user space to put the 169 system into a sleep state while taking into account the 170 concurrent arrival of wakeup events. Reading from it returns 171 the current number of registered wakeup events and it blocks if 172 some wakeup events are being processed at the time the file is 173 read from. Writing to it will only succeed if the current 174 number of wakeup events is equal to the written value and, if 175 successful, will make the kernel abort a subsequent transition 176 to a sleep state if any wakeup events are reported after the 177 write has returned. 178 179What: /sys/power/reserved_size 180Date: May 2011 181Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 182Description: 183 The /sys/power/reserved_size file allows user space to control 184 the amount of memory reserved for allocations made by device 185 drivers during the "device freeze" stage of hibernation. It can 186 be written a string representing a non-negative integer that 187 will be used as the amount of memory to reserve for allocations 188 made by device drivers' "freeze" callbacks, in bytes. 189 190 Reading from this file will display the current value, which is 191 set to 1 MB by default. 192 193What: /sys/power/autosleep 194Date: April 2012 195Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 196Description: 197 The /sys/power/autosleep file can be written one of the strings 198 returned by reads from /sys/power/state. If that happens, a 199 work item attempting to trigger a transition of the system to 200 the sleep state represented by that string is queued up. This 201 attempt will only succeed if there are no active wakeup sources 202 in the system at that time. After every execution, regardless 203 of whether or not the attempt to put the system to sleep has 204 succeeded, the work item requeues itself until user space 205 writes "off" to /sys/power/autosleep. 206 207 Reading from this file causes the last string successfully 208 written to it to be returned. 209 210What: /sys/power/wake_lock 211Date: February 2012 212Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 213Description: 214 The /sys/power/wake_lock file allows user space to create 215 wakeup source objects and activate them on demand (if one of 216 those wakeup sources is active, reads from the 217 /sys/power/wakeup_count file block or return false). When a 218 string without white space is written to /sys/power/wake_lock, 219 it will be assumed to represent a wakeup source name. If there 220 is a wakeup source object with that name, it will be activated 221 (unless active already). Otherwise, a new wakeup source object 222 will be registered, assigned the given name and activated. 223 If a string written to /sys/power/wake_lock contains white 224 space, the part of the string preceding the white space will be 225 regarded as a wakeup source name and handled as descrived above. 226 The other part of the string will be regarded as a timeout (in 227 nanoseconds) such that the wakeup source will be automatically 228 deactivated after it has expired. The timeout, if present, is 229 set regardless of the current state of the wakeup source object 230 in question. 231 232 Reads from this file return a string consisting of the names of 233 wakeup sources created with the help of it that are active at 234 the moment, separated with spaces. 235 236 237What: /sys/power/wake_unlock 238Date: February 2012 239Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 240Description: 241 The /sys/power/wake_unlock file allows user space to deactivate 242 wakeup sources created with the help of /sys/power/wake_lock. 243 When a string is written to /sys/power/wake_unlock, it will be 244 assumed to represent the name of a wakeup source to deactivate. 245 If a wakeup source object of that name exists and is active at 246 the moment, it will be deactivated. 247 248 Reads from this file return a string consisting of the names of 249 wakeup sources created with the help of /sys/power/wake_lock 250 that are inactive at the moment, separated with spaces. 251 252What: /sys/power/pm_print_times 253Date: May 2012 254Contact: Sameer Nanda <snanda@chromium.org> 255Description: 256 The /sys/power/pm_print_times file allows user space to 257 control whether the time taken by devices to suspend and 258 resume is printed. These prints are useful for hunting down 259 devices that take too long to suspend or resume. 260 261 Writing a "1" enables this printing while writing a "0" 262 disables it. The default value is "0". Reading from this file 263 will display the current value. 264 265What: /sys/power/pm_wakeup_irq 266Date: April 2015 267Contact: Alexandra Yates <alexandra.yates@linux.intel.org> 268Description: 269 The /sys/power/pm_wakeup_irq file reports to user space the IRQ 270 number of the first wakeup interrupt (that is, the first 271 interrupt from an IRQ line armed for system wakeup) seen by the 272 kernel during the most recent system suspend/resume cycle. 273 274 This output is useful for system wakeup diagnostics of spurious 275 wakeup interrupts. 276 277What: /sys/power/pm_debug_messages 278Date: July 2017 279Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 280Description: 281 The /sys/power/pm_debug_messages file controls the printing 282 of debug messages from the system suspend/hiberbation 283 infrastructure to the kernel log. 284 285 Writing a "1" to this file enables the debug messages and 286 writing a "0" (default) to it disables them. Reads from 287 this file return the current value. 288