[MinnowBoard] how to enable gpio wake up function

[xing_wei at linux.intel.com]

I'm working on the minnowmax board, and i want the gpio 84(GPIO_S5_4) to
be a wakeup source that can
wake up the system from S3 like the switch key does on board.
My yocto linux kernel version is 3.14.4.
I've referenced the doc named
"510858_BayTrail_I_SoC_External_Design_Spec_r1p0" and the kernel driver
code named pinctrl-baytrail.c.
The registers about gpio in baytrail are divided into kinds, IO access
registers and memory mapped access registers.
The pinctrl-baytrail.c just read/write memory mapped access register.   
Seems like no corresponding bit in memory mapped access register can
enable the wake up function.
My operation is request gpio 84 first, then request a interrupt with
IRQF_TRIGGER_RISING, IRQF_TRIGGER_FALLING, IRQF_ONESHOT, IRQF_NO_SUSPEND.
And irq function works during kernel runtime, but can't wake the system up
from S3.
My question is how to use GPIO_S5 as a wake up source on minnowmax board?
Expect your help.
Thanks.