I'm building Android for a custom iMX8 board. Android is working fine when booting from the SD card.
I've used uuu to put the exact same partition images on the onboard eMMC flash.
I can see the partitions on the eMMC (and SD card) after booting Android from the SD card:
smarc_mx8mq:/dev/block # ls
by-name loop5 mmcblk0boot1 mmcblk0p14 mmcblk0p4 mmcblk1 mmcblk1p14 mmcblk1p4 platform ram13 ram5 zram0
loop0 loop6 mmcblk0p1 mmcblk0p15 mmcblk0p5 mmcblk1p1 mmcblk1p15 mmcblk1p5 ram0 ram14 ram6
loop1 loop7 mmcblk0p10 mmcblk0p16 mmcblk0p6 mmcblk1p10 mmcblk1p16 mmcblk1p6 ram1 ram15 ram7
loop2 loop8 mmcblk0p11 mmcblk0p17 mmcblk0p7 mmcblk1p11 mmcblk1p17 mmcblk1p7 ram10 ram2 ram8
loop3 mmcblk0 mmcblk0p12 mmcblk0p2 mmcblk0p8 mmcblk1p12 mmcblk1p2 mmcblk1p8 ram11 ram3 ram9
loop4 mmcblk0boot0 mmcblk0p13 mmcblk0p3 mmcblk0p9 mmcblk1p13 mmcblk1p3 mmcblk1p9 ram12 ram4 vold
When I try to boot from eMMC I get the error:
fsl_avb_ab_flow.c:1182: ERROR: No bootable slots found.
I can boot to u-boot from the eMMC and use the command fastboot usb 0 to put it in fastboot mode.
Using fastboot flash boot boot.img from the host PC fails too, with a similar error:
error: Failed to identify current slot.
Diffing the results of fastboot getvar all with SD card, compared to eMMC, I see the following differences:
8c8
< (bootloader) erase-block-size:0x200
---
> (bootloader) erase-block-size:0x80000
40c40
< (bootloader) partition-size:all:0x3b5980000
---
> (bootloader) partition-size:all:0xece000000
75c75
< (bootloader) current-slot:a
---
> (bootloader) current-slot:no bootable slot
77c77
< (bootloader) slot-successful:a:yes
---
> (bootloader) slot-successful:a:no
79,80c79,80
< (bootloader) slot-unbootable:a:no
< (bootloader) slot-unbootable:b:no
---
> (bootloader) slot-unbootable:a:yes
> (bootloader) slot-unbootable:b:yes
82c82
< (bootloader) slot-retry-count:b:7
---
> (bootloader) slot-retry-count:b:0
84c84
< finished. total time: 0.009s
---
> finished. total time: 0.005s
So there's definitely a problem with the A/B slots on the eMMC.
I've tried fastboot --set-active=a, while it outputs:
Setting current slot to 'a'...
OKAY [ 0.007s]
finished. total time: 0.007s
it doesn't fix anything.
My questions are:
Where is all this A/B information stored?
How do I make a bootable slot?
I was able to fix this with fastboot --set-active=a followed immediately by fastboot flash boot boot.img and all the other partitions.