ENGR00133978 PM: add time sensitive debug function to suspend & resume
There was some driver is slow on suspend/resume,
but some embeded system like eReader,Cellphone
are time sensitive,this commit will report the slow
driver on suspend/resume, the default value is 500us(0.5ms)
Also, the threshold can be change by modify
'/sys/power/device_suspend_time_threshold' to change the threshold,
it is in microsecond.
The output is like:
PM: device platform:soc-audio.2 suspend too slow, takes 606.696 msecs
PM: device platform:mxc_sdc_fb.1 suspend too slow, takes 7.708 msecs
the default state of suspend driver is default off,
if you want to debug the suspend time, echo time in
microsecond(u Second) to /sys/powe/device_suspend_time_threshold
eg: I want to know which driver suspend & resume takes
more that 0.5 ms (500 us), you can just :