[U-Boot] SPL load ARM Trusted Firmware BL31?

[Masahiro Yamada]

Hi Michal,


2016-10-05 23:39 GMT+09:00 Michal Simek <monstr at monstr.eu>:
> Hi Masahiro,
>
> 2016-10-04 20:19 GMT-07:00 Masahiro Yamada <yamada.masahiro at socionext.com>:
>
>> Hi.
>>
>> Recently I implemented ARM Trusted Firmware BL31 for my SoCs.
>>
>> But, I am wondering how the boot-flow should be.
>>
>>
>>
>> Here is my situation.
>>
>>
>> [1]
>> When my company developed its first ARMv8 SoC,
>> I had to bring up the system very quickly.
>>
>> I was familiar with U-Boot and Linux to some extent, but not with ATF
>> at that time.
>> Also I was too pressed, so I decided to build up the system without ATF.
>>
>> The boot-flow was like this:
>>
>>   BootROM  ->  U-Boot SPL  -> U-Boot proper -> Linux
>>
>> In this flow, the secure runtime firmware is missing,
>> so I used Spin-Table for the enable-method.
>>
>>
>> [2]
>> Now I finished porting ATF BL31.
>> The low-level init code (basic SoC init + DRAM initialization)
>> already exists in U-Boot SPL.
>> So, I am currently re-using SPL, like follows:
>>
>>  BootROM ->  U-Boot SPL  -> ATF BL31 -> U-Boot proper (=BL33) -> Linux
>>
>>
>> As far as I know, SPL can not load multiple images such as BL31, BL32, BL33
>> (here BL32 is optional).
>> So, I hacked my SPL to load multi images
>> and jump to BL31.
>>
>
> this is not entirely truth. If you look at zynqmp you will find out that if
> you
> work with atf as kernel and full u-boot as dtb then u-boot SPL can load two
> images.
> This is what I use. It is a trick but I am not using any changes to get it
> work.


Ah, now I see.

The idea I came up with was
to put every ATF stuff into spl_board_prepare_for_boot().



>
> We are using only BL31 and nothing else.


But, prior to commit f3d1cc2ff387ffe22ccd1bdcb2a998ec46149c6d
(ARM64: zynqmp: Enable SPL for all zynqmp boards),

BootROM -> fsbl -> ATF BL31 -> U-Boot -> Linux

was the only supported solution, yes?



>>
>>
>> Recently I saw Simon's binman patches.
>> It provides a fancy way to pack multiple firmware components into a
>> single image,
>> but I did not see the systematic way to load every entry in the image.
>>   (under way?)
>>
>>
>> I was wondering if I should move my low-level init code
>> from SPL to ATF BL2 or somewhere.
>>
>> Comments are welcome.
>>
>
> I use bootrom -> SPL -> ATF -> full u-boot.
>
> I want to use SPL because we have all device drivers in u-boot and
> in ATF we have only serial driver. If you want to use BL2 just for low
> level init stuff
> you can but it is the question if this brings you any value.


Yes.  This is one big advantage of using SPL over BL2.




-- 
Best Regards
Masahiro Yamada