I follow instruction on https://source.android.com/source/devices to get linux kernel android-hikey-linaro-4.9.
After build success, I replace hi6220-hikey.dtb-4.9 and Image-dtb-4.9, generate android-8.0.0_r4 boot.img and system.img.
After burning *.img successfully, hikey boot up android 8.0 but bluetooth doesn't work.
The commit id of android-hikey-linaro-4.9 I used is
Does anyone have any idea about this problem?