env: am57xx: Implement A/B boot process
Add support for A/B boot process on AM57xx based boards:
1. Define 'slot_suffix' variable (using 'ab_select' command)
2. Extend 'emmc_android_boot' boot command (add commands for A/B boot
process)
'ab_select' command is used to decide which slot should be used for
booting up. A/B metadata resides in 'misc' partition.
To activate the A/B boot process, the following config options must be
set:
CONFIG_ANDROID_AB=y
CONFIG_CMD_AB_SELECT=y
For successful A/B boot, the corresponding A/B infrastructure must be
involved on Android side [1] (including mounting system as root), and
disk must be partitioned accordingly.
When A/B boot is enabled, there are some known limitations currently
exist (not related to A/B patches, need to be implemented later):
1. The 'Verified Boot' sequence is not supported
2. dev path to system partition (system_a or system_b) is passed via
'bootargs' as 'root=' argument like 'root=/dev/mmcblk1p12', but
further we'll need to rework it with respect to dm-verity
requirements [2]
In case when A/B partitions are not present in system (and A/B boot is
enabled), boot up process will be terminated and next message will be
shown:
"boot_a(b) partition not found"
[1] https://source.android.com/devices/tech/ota/ab
[2] https://source.android.com/devices/tech/ota/ab/ab_implement#kernel
Signed-off-by: Ruslan Trofymenko <ruslan.trofymenko@linaro.org>
Signed-off-by: Igor Opaniuk <igor.opaniuk@gmail.com>
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Alistair Strachan <astrachan@google.com>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed