This patch series adds support for Android A/B boot process [1]. Main steps of A/B boot process are: - A/B metadata integrity check - looking for the current slot (where the system should be booting from) - getting the name of the current boot partition (boot_a or boot_b) and loading the corresponding Android boot image - getting the name of the current system partition (system_a or system_b) and passing of its full name via kernel command line (like 'root=/dev/mmcblk1p11') - passing current slot via kernel command line (like 'androidboot.slot_suffix=_a') and via A/B metadata (e.g. via misc partition) - A/B metadata processing: setting the boot success flag for current slot, handling the retry counter, etc
A/B metadata is organized according to Android reference [2] and stored on 'misc' partition. On the first A/B boot process, when 'misc' partition doesn't contain required data, default A/B metadata will be created and stored in 'misc' partition. In the end of the Android boot, 'update_verifier' and 'update_engine' services are processing the A/B metadata through the Boot Control HAL. To confirm the boot was successful using current slot, "boot success" flag must be set on Android side.
To enable Android A/B support in U-Boot: 1. Set the following config options:
CONFIG_ANDROID_AB=y CONFIG_CMD_ANDROID_AB_SELECT=y
2. Change the disk layout so that it has sloted boot partitions. E.g. instead of 'boot' and 'system' partitions there should be 'boot_a', 'boot_b', 'system_a' and 'system_b' partitions.
To be able to actually test this patch series, the A/B features must be implemented and enabled in Android as well (see [1] for details).
Documentation and corresponding test for A/B boot is present here. The last patch in this series integrates A/B boot support on AM57xx based boards (though it's not enabled by default). Future users of A/B boot feature can use it as a reference.
This series is a part of previous submission [3] by Alex Deymo. It contains only A/B feature that was stripped out from there with some modifications for using with "bootm" command preferred in upstream.
[1] https://source.android.com/devices/tech/ota/ab/ab_implement [2] bootable/recovery/bootloader_message/include/bootloader_message/bootloader_message.h [3] https://lists.denx.de/pipermail/u-boot/2017-April/285841.html
Ruslan Trofymenko (7): cmd: part: Add 'number' sub-command disk: part: Extend API to get partition info common: Implement A/B metadata cmd: Add 'android_ab_select' command test/py: Add base test case for A/B updates doc: android: Add simple guide for A/B updates env: am57xx: Implement A/B boot process
cmd/Kconfig | 11 ++ cmd/Makefile | 1 + cmd/android_ab_select.c | 53 +++++++ cmd/part.c | 16 +- common/Kconfig | 10 ++ common/Makefile | 1 + common/android_ab.c | 278 +++++++++++++++++++++++++++++++++++ configs/sandbox_defconfig | 2 + disk/part.c | 68 +++++++++ doc/README.android-ab | 67 +++++++++ include/android_ab.h | 34 +++++ include/android_bootloader_message.h | 164 +++++++++++++++++++++ include/environment/ti/boot.h | 44 +++++- include/part.h | 21 +++ test/py/tests/test_ab.py | 74 ++++++++++ 15 files changed, 839 insertions(+), 5 deletions(-) create mode 100644 cmd/android_ab_select.c create mode 100644 common/android_ab.c create mode 100644 doc/README.android-ab create mode 100644 include/android_ab.h create mode 100644 include/android_bootloader_message.h create mode 100644 test/py/tests/test_ab.py