[sysfs for runtime PM]
#cd /sys/bus/mmc/devices/mmc1:0001/power
# ls -la
-rw-r--r-- root root 4096 1970-01-01 03:50 autosuspend_delay_ms
-rw-r--r-- root root 4096 1970-01-01 03:50 control
-r--r--r-- root root 4096 1970-01-01 03:50 runtime_active_time
-r--r--r-- root root 4096 1970-01-01 03:50 runtime_status
-r--r--r-- root root 4096 1970-01-01 03:50 runtime_suspended_time
# cat ./control
auto
# cat ./runtime_status
active
# cat ./runtime_status
suspended
[Source file]
kernel/drivers/base/power/sysfs.c
/*
* control - Report/change current runtime PM setting of the device
*
* Runtime power management of a device can be blocked with the help of
* this attribute. All devices have one of the following two values for
* the power/control file:
*
* + "auto\n" to allow the device to be power managed at run time;
* + "on\n" to prevent the device from being power managed at run time;
*
* The default for all devices is "auto", which means that devices may be
* subject to automatic power management, depending on their drivers.
* Changing this attribute to "on" prevents the driver from power managing
* the device at run time. Doing that while the device is suspended causes
* it to be woken up.
