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