[U-Boot] Appended DTB Android boot image support

[Simon Glass]

Hi,

On 1 May 2018 at 04:52, Ramon Fried <ramon.fried at gmail.com> wrote:
> On Tue, May 1, 2018 at 12:20 PM, Alex Deymo <deymo+ at google.com> wrote:
>> Hi Ramon,
>>
>> What "header_version" is the boot image you have? The
>> include/android_image.h in U-Boot is a little bit old so it only defines
the
>> v0 format. The "unused" field in v0 was renamed to "header_version"
where 0
>> means v0. The v1 adds a few more fields, including a DTB/DTBO for
*recovery*
>> mode.
>> See
>>
https://android.googlesource.com/platform/system/core/+/master/mkbootimg/include/bootimg/bootimg.h
>>
> Yes, the U-boot has the v0 version.
>
>> Having multiple DTs and picking one or merge overlays at runtime is a
>> reasonable thing and there's some documentation in AOSP on how to do it
in
>> Android: https://source.android.com/devices/architecture/dto/multiple
(and
>> other sections around it). There are some options on where to store these
>> and even a supported format for placing multiple .dtbo in a single "dtbo"
>> partition (but appending multiple DTBs at the end of the kernel is not
one
>> of these).
>>
>> Which are the "seconday" fields you are referring to?
>
> uint32_t second_size; /* size in bytes */
> uint32_t second_addr; /* physical load addr */
>
> In
https://android.googlesource.com/platform/system/core/+/master/mkbootimg/include/bootimg/bootimg.h
>>
>> I'm not familiar with the Dragonboard images, but it looks like they just
>> extended this over the reserved space in a different way. Maybe you can
>> convert the header to the newer format, but that still requires work in
>> U-Boot to support the new format.
> I'm willing to do it, I just want to get some approval from
> maintainers before I dive in.
>
> Thanks,
> Ramon
>>
>> Regards,
>> Alex
>>
>>
>> Le lun. 30 avr. 2018 à 16:17, Ramon Fried <ramon.fried at gmail.com> a
écrit :
>>>
>>> Hi all.
>>> I'm currently adding support for Qualcomm Dragonboards  to U-boot as a
>>> primary bootloader without chain-loading using LK which is currently
>>> already supported in mainline U-boot.
>>>
>>> Qualcomm Android images are regular android images where the DTB's are
>>> appended to the image. Qualcomm used the "unused" field in the image
>>> header to populate the size of the DTB *.
>>>
>>> I'm looking for a more standard version for supporting these kind of
>>> images.
>>> Currently, to boot these images, you must provide DTB somewhere in mem
>>> and provide it as argument to bootm for instance.
>>>
>>> My goal is to add support that U-boot will parse the image, see that
>>> the DTB is included and use that as the FDT automatically.
>>>
>>> I'm looking at the "secondary" fields which are currently not used as
>>> a valid option to point to the DTB and it's size.
>>>
>>> Do you know if someone is working on something similar, or do you have
>>> any suggestions for the right approach to this issue ?

Does every vendor just do its own thing, or is there a standard header
structure?

How can we detect multiple incompatible options? Just by the machine
architecture?

Can we just use FIT perhaps?

>>>
>>> Thanks,
>>> Ramon
>>>
>>> * - Actually, Qualcomm appends a pack of DTBs with offset table and
>>> chooses the right DTB in runtime.
>>> _______________________________________________
>>> U-Boot mailing list
>>> U-Boot at lists.denx.de
>>> https://lists.denx.de/listinfo/u-boot

Regards,
Simon