Bluetooth Low Energy disconnects when entering sleep

REPRODUCIBILITY (% or how often): 100%
BUILD ID = OS VERSION (Settings > About product): 4.2.0.21
HARDWARE (XA2, X10, X10 II, …): XA2 Plus
UI LANGUAGE: Irrelevant
REGRESSION: (compared to previous public release: Yes, No, ?): Unknown

DESCRIPTION:

BLE devices disconnect when the device enters sleep mode. Noticed this with a PineTime device. When the phone screen stays on (e.g. when the phone is charging) the connection is rock-solid. When the phone enters sleep, though, the connection drops.

I’ve of course tried to set the suspend policy with mcetool. While this reduces the frequency of the disconnects, it doesn’t solve the issue entirely. Somehow, something is powered down that shouldn’t be.

PRECONDITIONS:

STEPS TO REPRODUCE:

  1. Connect a BLE device
  2. Turn off the screen
  3. Wait a few minutes

EXPECTED RESULT:

The connection is stable and is not interrupted

ACTUAL RESULT:

The connection is dropped

ADDITIONAL INFORMATION:

(Please ALWAYS attach relevant data such as logs, screenshots, etc…)