[U-Boot] [PATCH 1/2] ARMv8: add optional Linux kernel image header

[Stephen Warren]

On 01/03/2018 10:56 AM, Tom Rini wrote:
> On Wed, Jan 03, 2018 at 10:42:56AM -0700, Stephen Warren wrote:
>> On 01/03/2018 06:45 AM, Tom Rini wrote:
>>> On Tue, Jan 02, 2018 at 04:54:21PM -0700, Stephen Warren wrote:
>>>
>>>> From: Stephen Warren <swarren at nvidia.com>
>>>>
>>>> Allow placing a Linux kernel image header at the start of the U-Boot
>>>> binary. This is useful since the image header reports the amount of memory
>>>> (BSS and similar) that U-Boot needs to use, but that isn't part of the
>>>> binary size. This can be used by the code that loads U-Boot into memory to
>>>> determine where to load U-Boot, based on other users of memory.
>>>>
>>>> Signed-off-by: Stephen Warren <swarren at nvidia.com>
>>>> ---
>>>> This series relies (at the very least for diff context) on the previous
>>>> series I sent Dec 19: ARM: tegra: don't use CONFIG_SPL_TEXT_BASE when no
>>>> SPL ... ARM: tegra: use CONFIG_SYS_INIT_SP_BSS_OFFSET.
>>>
>>> Neat.  Are the Linux folks encouraging other projects to re-use this
>>> header?
>>
>> Not that I'm aware of, but mainly because I haven't talked to upstream
>> kernel people about this at all. I implemented this because in recent
>> versions of Linux4Tegra, for all 64-bit SoCs, our main CPU EL2/EL1 boot path
>> is either:
>>
>> cboot -> Linux kernel
>> cboot -> U-Boot -> Linux kernel
>>
>> cboot is an NVIDIA binary bootloader. cboot wants to know about BSS/...
>> usage of the binary it loads, which can be determined from the Linux kernel
>> image header, but we don't want cboot to take different paths when booting
>> Linux or U-Boot (or indeed anything at all), so the simplest thing was to
>> make U-Boot look as identical to a Linux kernel as possible.
>>
>>> Is there somewhere we can point to as reference for the format
>>> for the Kconfig help as well, not just the text?  Thanks!
>>
>> The Linux kernel file Documentation/arm64/booting.txt does describe the
>> format. Should I respin and add that filename to the Kconfig text?
> 
> Yes, and I feel like it can't hurt to let the arm64 maintainers know too
> as frankly it's a good idea and more projects should make use of it, so
> maybe it should be a bit more formally documented (in one of those fancy
> new rst files?) or something.

I talked to Catalin Marinas (one of the arch/arm64 maintainers) on IRC 
and he said he didn't see any issue with this approach.