Add support for A/B boot process on AM57xx based boards:
1. Define 'slot_suffix' variable (using 'android_ab_select' command) 2. Extend 'emmc_android_boot' boot command (add commands for A/B boot process)
'android_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_ANDROID_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 --- include/environment/ti/boot.h | 44 +++++++++++++++++++++++++++++++++++++++---- 1 file changed, 40 insertions(+), 4 deletions(-)
diff --git a/include/environment/ti/boot.h b/include/environment/ti/boot.h index 3c9c87f..3ace316 100644 --- a/include/environment/ti/boot.h +++ b/include/environment/ti/boot.h @@ -63,6 +63,36 @@ #define AVB_VERIFY_CMD "" #endif
+#define CONTROL_PARTITION "misc" + +#if defined(CONFIG_CMD_ANDROID_AB_SELECT) +#define AB_SELECT \ + "if part number mmc 1 " CONTROL_PARTITION " control_part_number; " \ + "then " \ + "echo " CONTROL_PARTITION \ + " partition number:${control_part_number};" \ + "android_ab_select slot_name " \ + "mmc ${mmcdev}:${control_part_number};" \ + "else " \ + "echo " CONTROL_PARTITION " partition not found;" \ + "exit;" \ + "fi;" \ + "setenv slot_suffix _${slot_name};" \ + "if part number mmc ${mmcdev} system${slot_suffix} " \ + "system_part_number; then " \ + "setenv bootargs_ab " \ + "ro root=/dev/mmcblk${mmcdev}p${system_part_number} " \ + "rootwait init=/init skip_initramfs " \ + "androidboot.slot_suffix=${slot_suffix};" \ + "echo A/B cmdline addition: ${bootargs_ab};" \ + "setenv bootargs ${bootargs} ${bootargs_ab};" \ + "else " \ + "echo system${slot_suffix} partition not found;" \ + "fi;" +#else +#define AB_SELECT "" +#endif + #define DEFAULT_COMMON_BOOT_TI_ARGS \ "console=" CONSOLEDEV ",115200n8\0" \ "fdtfile=undefined\0" \ @@ -91,10 +121,16 @@ "mmc dev $mmcdev; " \ "mmc rescan; " \ AVB_VERIFY_CHECK \ - "part start mmc ${mmcdev} boot boot_start; " \ - "part size mmc ${mmcdev} boot boot_size; " \ - "mmc read ${loadaddr} ${boot_start} ${boot_size}; " \ - "bootm ${loadaddr}#${fdtfile};\0 " + AB_SELECT \ + "if part start mmc ${mmcdev} boot${slot_suffix} boot_start; " \ + "then " \ + "part size mmc ${mmcdev} boot${slot_suffix} " \ + "boot_size; " \ + "mmc read ${loadaddr} ${boot_start} ${boot_size}; " \ + "bootm ${loadaddr}#${fdtfile}; " \ + "else " \ + "echo boot${slot_suffix} partition not found; " \ + "fi;\0"
#ifdef CONFIG_OMAP54XX