1What: /sys/devices/.../power/ 2Date: January 2009 3Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 4Description: 5 The /sys/devices/.../power directory contains attributes 6 allowing the user space to check and modify some power 7 management related properties of given device. 8 9What: /sys/devices/.../power/wakeup 10Date: January 2009 11Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 12Description: 13 The /sys/devices/.../power/wakeup attribute allows the user 14 space to check if the device is enabled to wake up the system 15 from sleep states, such as the memory sleep state (suspend to 16 RAM) and hibernation (suspend to disk), and to enable or disable 17 it to do that as desired. 18 19 Some devices support "wakeup" events, which are hardware signals 20 used to activate the system from a sleep state. Such devices 21 have one of the following two values for the sysfs power/wakeup 22 file: 23 24 + "enabled\n" to issue the events; 25 + "disabled\n" not to do so; 26 27 In that cases the user space can change the setting represented 28 by the contents of this file by writing either "enabled", or 29 "disabled" to it. 30 31 For the devices that are not capable of generating system wakeup 32 events this file is not present. In that case the device cannot 33 be enabled to wake up the system from sleep states. 34 35What: /sys/devices/.../power/control 36Date: January 2009 37Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 38Description: 39 The /sys/devices/.../power/control attribute allows the user 40 space to control the run-time power management of the device. 41 42 All devices have one of the following two values for the 43 power/control file: 44 45 + "auto\n" to allow the device to be power managed at run time; 46 + "on\n" to prevent the device from being power managed; 47 48 The default for all devices is "auto", which means that they may 49 be subject to automatic power management, depending on their 50 drivers. Changing this attribute to "on" prevents the driver 51 from power managing the device at run time. Doing that while 52 the device is suspended causes it to be woken up. 53 54What: /sys/devices/.../power/async 55Date: January 2009 56Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 57Description: 58 The /sys/devices/.../async attribute allows the user space to 59 enable or diasble the device's suspend and resume callbacks to 60 be executed asynchronously (ie. in separate threads, in parallel 61 with the main suspend/resume thread) during system-wide power 62 transitions (eg. suspend to RAM, hibernation). 63 64 All devices have one of the following two values for the 65 power/async file: 66 67 + "enabled\n" to permit the asynchronous suspend/resume; 68 + "disabled\n" to forbid it; 69 70 The value of this attribute may be changed by writing either 71 "enabled", or "disabled" to it. 72 73 It generally is unsafe to permit the asynchronous suspend/resume 74 of a device unless it is certain that all of the PM dependencies 75 of the device are known to the PM core. However, for some 76 devices this attribute is set to "enabled" by bus type code or 77 device drivers and in that cases it should be safe to leave the 78 default value. 79 80What: /sys/devices/.../power/wakeup_count 81Date: September 2010 82Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 83Description: 84 The /sys/devices/.../wakeup_count attribute contains the number 85 of signaled wakeup events associated with the device. This 86 attribute is read-only. If the device is not capable to wake up 87 the system from sleep states, this attribute is not present. 88 If the device is not enabled to wake up the system from sleep 89 states, this attribute is empty. 90 91What: /sys/devices/.../power/wakeup_active_count 92Date: September 2010 93Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 94Description: 95 The /sys/devices/.../wakeup_active_count attribute contains the 96 number of times the processing of wakeup events associated with 97 the device was completed (at the kernel level). This attribute 98 is read-only. If the device is not capable to wake up the 99 system from sleep states, this attribute is not present. If 100 the device is not enabled to wake up the system from sleep 101 states, this attribute is empty. 102 103What: /sys/devices/.../power/wakeup_abort_count 104Date: February 2012 105Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 106Description: 107 The /sys/devices/.../wakeup_abort_count attribute contains the 108 number of times the processing of a wakeup event associated with 109 the device might have aborted system transition into a sleep 110 state in progress. This attribute is read-only. If the device 111 is not capable to wake up the system from sleep states, this 112 attribute is not present. If the device is not enabled to wake 113 up the system from sleep states, this attribute is empty. 114 115What: /sys/devices/.../power/wakeup_expire_count 116Date: February 2012 117Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 118Description: 119 The /sys/devices/.../wakeup_expire_count attribute contains the 120 number of times a wakeup event associated with the device has 121 been reported with a timeout that expired. This attribute is 122 read-only. If the device is not capable to wake up the system 123 from sleep states, this attribute is not present. If the 124 device is not enabled to wake up the system from sleep states, 125 this attribute is empty. 126 127What: /sys/devices/.../power/wakeup_active 128Date: September 2010 129Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 130Description: 131 The /sys/devices/.../wakeup_active attribute contains either 1, 132 or 0, depending on whether or not a wakeup event associated with 133 the device is being processed (1). This attribute is read-only. 134 If the device is not capable to wake up the system from sleep 135 states, this attribute is not present. If the device is not 136 enabled to wake up the system from sleep states, this attribute 137 is empty. 138 139What: /sys/devices/.../power/wakeup_total_time_ms 140Date: September 2010 141Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 142Description: 143 The /sys/devices/.../wakeup_total_time_ms attribute contains 144 the total time of processing wakeup events associated with the 145 device, in milliseconds. This attribute is read-only. If the 146 device is not capable to wake up the system from sleep states, 147 this attribute is not present. If the device is not enabled to 148 wake up the system from sleep states, this attribute is empty. 149 150What: /sys/devices/.../power/wakeup_max_time_ms 151Date: September 2010 152Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 153Description: 154 The /sys/devices/.../wakeup_max_time_ms attribute contains 155 the maximum time of processing a single wakeup event associated 156 with the device, in milliseconds. This attribute is read-only. 157 If the device is not capable to wake up the system from sleep 158 states, this attribute is not present. If the device is not 159 enabled to wake up the system from sleep states, this attribute 160 is empty. 161 162What: /sys/devices/.../power/wakeup_last_time_ms 163Date: September 2010 164Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 165Description: 166 The /sys/devices/.../wakeup_last_time_ms attribute contains 167 the value of the monotonic clock corresponding to the time of 168 signaling the last wakeup event associated with the device, in 169 milliseconds. This attribute is read-only. If the device is 170 not enabled to wake up the system from sleep states, this 171 attribute is not present. If the device is not enabled to wake 172 up the system from sleep states, this attribute is empty. 173 174What: /sys/devices/.../power/wakeup_prevent_sleep_time_ms 175Date: February 2012 176Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 177Description: 178 The /sys/devices/.../wakeup_prevent_sleep_time_ms attribute 179 contains the total time the device has been preventing 180 opportunistic transitions to sleep states from occurring. 181 This attribute is read-only. If the device is not capable to 182 wake up the system from sleep states, this attribute is not 183 present. If the device is not enabled to wake up the system 184 from sleep states, this attribute is empty. 185 186What: /sys/devices/.../power/autosuspend_delay_ms 187Date: September 2010 188Contact: Alan Stern <stern@rowland.harvard.edu> 189Description: 190 The /sys/devices/.../power/autosuspend_delay_ms attribute 191 contains the autosuspend delay value (in milliseconds). Some 192 drivers do not want their device to suspend as soon as it 193 becomes idle at run time; they want the device to remain 194 inactive for a certain minimum period of time first. That 195 period is called the autosuspend delay. Negative values will 196 prevent the device from being suspended at run time (similar 197 to writing "on" to the power/control attribute). Values >= 198 1000 will cause the autosuspend timer expiration to be rounded 199 up to the nearest second. 200 201 Not all drivers support this attribute. If it isn't supported, 202 attempts to read or write it will yield I/O errors. 203 204What: /sys/devices/.../power/pm_qos_resume_latency_us 205Date: March 2012 206Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 207Description: 208 The /sys/devices/.../power/pm_qos_resume_latency_us attribute 209 contains the PM QoS resume latency limit for the given device, 210 which is the maximum allowed time it can take to resume the 211 device, after it has been suspended at run time, from a resume 212 request to the moment the device will be ready to process I/O, 213 in microseconds. If it is equal to 0, however, this means that 214 the PM QoS resume latency may be arbitrary and the special value 215 "n/a" means that user space cannot accept any resume latency at 216 all for the given device. 217 218 Not all drivers support this attribute. If it isn't supported, 219 it is not present. 220 221 This attribute has no effect on system-wide suspend/resume and 222 hibernation. 223 224What: /sys/devices/.../power/pm_qos_latency_tolerance_us 225Date: January 2014 226Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 227Description: 228 The /sys/devices/.../power/pm_qos_latency_tolerance_us attribute 229 contains the PM QoS active state latency tolerance limit for the 230 given device in microseconds. That is the maximum memory access 231 latency the device can suffer without any visible adverse 232 effects on user space functionality. If that value is the 233 string "any", the latency does not matter to user space at all, 234 but hardware should not be allowed to set the latency tolerance 235 for the device automatically. 236 237 Reading "auto" from this file means that the maximum memory 238 access latency for the device may be determined automatically 239 by the hardware as needed. Writing "auto" to it allows the 240 hardware to be switched to this mode if there are no other 241 latency tolerance requirements from the kernel side. 242 243 This attribute is only present if the feature controlled by it 244 is supported by the hardware. 245 246 This attribute has no effect on runtime suspend and resume of 247 devices and on system-wide suspend/resume and hibernation. 248 249What: /sys/devices/.../power/pm_qos_no_power_off 250Date: September 2012 251Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 252Description: 253 The /sys/devices/.../power/pm_qos_no_power_off attribute 254 is used for manipulating the PM QoS "no power off" flag. If 255 set, this flag indicates to the kernel that power should not 256 be removed entirely from the device. 257 258 Not all drivers support this attribute. If it isn't supported, 259 it is not present. 260 261 This attribute has no effect on system-wide suspend/resume and 262 hibernation. 263 264What: /sys/devices/.../power/runtime_status 265Date: April 2010 266Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 267Description: 268 The /sys/devices/.../power/runtime_status attribute contains 269 the current runtime PM status of the device, which may be 270 "suspended", "suspending", "resuming", "active", "error" (fatal 271 error), or "unsupported" (runtime PM is disabled). 272