[U-Boot] Appended DTB Android boot image support

[Ramon Fried]

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 ?
>>
>> Thanks,
>> Ramon
>>
>> * - Actually, Qualcomm appends a pack of DTBs with offset table and
>> chooses the right DTB in runtime.
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