(Power Management) Cannot change power state of GPIO device

[yayembedded]

I have a BLE peripheral device using i2c, gpio.  When the peripheral is not connected I want the lowest power consumption possible.

when i try to turn off gpio:

//sleep
int err = device_set_power_state(gpio_dev, DEVICE_PM_OFF_STATE, NULL, NULL);

if (err) {
printk("power down not successful %d\n", err);
}

An error is returned, 0x86.  0x86 is not listed in errno.h so I don't know what it means. I also tried setting gpio to DEVICE_PM_LOW_POWER_STATE, but I get the same error.

Is changing gpio not allowed because it's too crucial for the device?

[Amanda Hsieh]

Hi, 

The whole GPIO peripheral can not be turned off. You have to set it to either "input" or "output". The default state is "input" which means "disconnected". 

Regards,
Amanda

[yayembedded]

Would setting it to "input" help with power management if something is connected to it?

[Amanda Hsieh]

Hi, 

Yes, there will not flow any current if the state is set to input/disconnected (this is the default state. in the PIN_CNF[n] register this corresponds to the value 2). 

-Amanda