1What: /sys/devices/.../power/ 2Date: January 2009 3Contact: Rafael J. Wysocki <rjw@sisk.pl> 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@sisk.pl> 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@sisk.pl> 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@sisk.pl> 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@sisk.pl> 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 enabled to wake up 87 the system from sleep states, this attribute is not present. 88 89What: /sys/devices/.../power/wakeup_active_count 90Date: September 2010 91Contact: Rafael J. Wysocki <rjw@sisk.pl> 92Description: 93 The /sys/devices/.../wakeup_active_count attribute contains the 94 number of times the processing of wakeup events associated with 95 the device was completed (at the kernel level). This attribute 96 is read-only. If the device is not enabled to wake up the 97 system from sleep states, this attribute is not present. 98 99What: /sys/devices/.../power/wakeup_abort_count 100Date: February 2012 101Contact: Rafael J. Wysocki <rjw@sisk.pl> 102Description: 103 The /sys/devices/.../wakeup_abort_count attribute contains the 104 number of times the processing of a wakeup event associated with 105 the device might have aborted system transition into a sleep 106 state in progress. This attribute is read-only. If the device 107 is not enabled to wake up the system from sleep states, this 108 attribute is not present. 109 110What: /sys/devices/.../power/wakeup_expire_count 111Date: February 2012 112Contact: Rafael J. Wysocki <rjw@sisk.pl> 113Description: 114 The /sys/devices/.../wakeup_expire_count attribute contains the 115 number of times a wakeup event associated with the device has 116 been reported with a timeout that expired. This attribute is 117 read-only. If the device is not enabled to wake up the system 118 from sleep states, this attribute is not present. 119 120What: /sys/devices/.../power/wakeup_active 121Date: September 2010 122Contact: Rafael J. Wysocki <rjw@sisk.pl> 123Description: 124 The /sys/devices/.../wakeup_active attribute contains either 1, 125 or 0, depending on whether or not a wakeup event associated with 126 the device is being processed (1). This attribute is read-only. 127 If the device is not enabled to wake up the system from sleep 128 states, this attribute is not present. 129 130What: /sys/devices/.../power/wakeup_total_time_ms 131Date: September 2010 132Contact: Rafael J. Wysocki <rjw@sisk.pl> 133Description: 134 The /sys/devices/.../wakeup_total_time_ms attribute contains 135 the total time of processing wakeup events associated with the 136 device, in milliseconds. This attribute is read-only. If the 137 device is not enabled to wake up the system from sleep states, 138 this attribute is not present. 139 140What: /sys/devices/.../power/wakeup_max_time_ms 141Date: September 2010 142Contact: Rafael J. Wysocki <rjw@sisk.pl> 143Description: 144 The /sys/devices/.../wakeup_max_time_ms attribute contains 145 the maximum time of processing a single wakeup event associated 146 with the device, in milliseconds. This attribute is read-only. 147 If the device is not enabled to wake up the system from sleep 148 states, this attribute is not present. 149 150What: /sys/devices/.../power/wakeup_last_time_ms 151Date: September 2010 152Contact: Rafael J. Wysocki <rjw@sisk.pl> 153Description: 154 The /sys/devices/.../wakeup_last_time_ms attribute contains 155 the value of the monotonic clock corresponding to the time of 156 signaling the last wakeup event associated with the device, in 157 milliseconds. This attribute is read-only. If the device is 158 not enabled to wake up the system from sleep states, this 159 attribute is not present. 160 161What: /sys/devices/.../power/autosuspend_delay_ms 162Date: September 2010 163Contact: Alan Stern <stern@rowland.harvard.edu> 164Description: 165 The /sys/devices/.../power/autosuspend_delay_ms attribute 166 contains the autosuspend delay value (in milliseconds). Some 167 drivers do not want their device to suspend as soon as it 168 becomes idle at run time; they want the device to remain 169 inactive for a certain minimum period of time first. That 170 period is called the autosuspend delay. Negative values will 171 prevent the device from being suspended at run time (similar 172 to writing "on" to the power/control attribute). Values >= 173 1000 will cause the autosuspend timer expiration to be rounded 174 up to the nearest second. 175 176 Not all drivers support this attribute. If it isn't supported, 177 attempts to read or write it will yield I/O errors. 178 179What: /sys/devices/.../power/pm_qos_latency_us 180Date: March 2012 181Contact: Rafael J. Wysocki <rjw@sisk.pl> 182Description: 183 The /sys/devices/.../power/pm_qos_resume_latency_us attribute 184 contains the PM QoS resume latency limit for the given device, 185 which is the maximum allowed time it can take to resume the 186 device, after it has been suspended at run time, from a resume 187 request to the moment the device will be ready to process I/O, 188 in microseconds. If it is equal to 0, however, this means that 189 the PM QoS resume latency may be arbitrary. 190 191 Not all drivers support this attribute. If it isn't supported, 192 it is not present. 193 194 This attribute has no effect on system-wide suspend/resume and 195 hibernation. 196