Why does my AOSP build (android-9.0.0_r47) fail to boot on Pixel 3a (sargo)?

[Dipanjan Das]

I have built an AOSP image (android-9.0.0_r47, build ID: PQ3B.190801.002) for Pixel 3a (sargo) from the source according to Google's official documentation. To flash the image, I have done the following:

• Booted into fastboot mode, and then TWRP
• Wiped Dalvik cache, system, data from TWRP to prevent dirty flash
• fastboot flashall -w flashed boot, dtbo, system, system_other and vbmeta images to respective partitions
• Reboot

A white flash screen with Google logo showed up for a split moment and then it went back to fastboot mode again. I retried flashing several times with different combinations. Several times I re-flashed the OTA image to go back to a "sane" state (fortunately official image boots every time) to start from scratch. Nothing helped.

Here is my build configuration:

============================================

PLATFORM_VERSION_CODENAME=REL

PLATFORM_VERSION=9

TARGET_PRODUCT=aosp_sargo

TARGET_BUILD_VARIANT=userdebug

TARGET_BUILD_TYPE=release

TARGET_ARCH=arm64

TARGET_ARCH_VARIANT=armv8-2a

TARGET_CPU_VARIANT=cortex-a75

TARGET_2ND_ARCH=arm

TARGET_2ND_ARCH_VARIANT=armv8-a

TARGET_2ND_CPU_VARIANT=cortex-a75

HOST_ARCH=x86_64

HOST_2ND_ARCH=x86

HOST_OS=linux

HOST_OS_EXTRA=Linux-4.15.0-70-generic-x86_64-Ubuntu-18.04.3-LTS

HOST_CROSS_OS=windows

HOST_CROSS_ARCH=x86

HOST_CROSS_2ND_ARCH=x86_64

HOST_BUILD_TYPE=release

BUILD_ID=PQ3B.190801.002

OUT_DIR=out

PRODUCT_SOONG_NAMESPACES=device/google/bonito hardware/google/av hardware/google/interfaces hardware/google/pixel hardware/qcom/sdm710 vendor/qcom/sdm710

============================================

Does anybody have any idea what might be going wrong?

[Robin Grimsmann]

I found a solution to this problem during my work on android-10.0.0_r35 for Pixel 3a (Sargo).

I suggest you do not have a vendor.img file in your ANDRID_PRODUCT_OUT folder?

You need to download the proprietary driver from https://developers.google.com/android/drivers#sargoqq2a.200501.001.b2. Make sure that your build id matches the file you download.

The archiv contains a shell - script, run it it will produce a vendor folder where you will find the vendor.img file. Copy it to your output folder.