[U-Boot] enbw_cmc, da850evm_direct_nor, and calimain vectors table misaligned

[Heiko Schocher <hs@denx.de>]

Hello Albert,

Am 11.06.2014 09:14, schrieb Albert ARIBAUD:
> Hi Masahiro,
>
> (to: the board maintainers for enbw_cmc, da850evm_direct_nor, and
> calimain)
>
> On Mon, 09 Jun 2014 18:29:26 +0900, Masahiro Yamada
> <yamada.m@jp.panasonic.com>  wrote:
>
>> Hi Albert,
>
>> You changed the behaviour of three boards,
>> "enbw_cmc", "da850evm_direct_nor", "calimain"!
>> Probably they are broken.
>>
>> These boards expects "0x00000011" (=CONFIG_SYS_DV_NOR_BOOT_CFG)
>> at the beginning of the image.
>> But since commit 41623c91, that is missing.
>>
>> If you still don't understand,  you should checkout   41623c91^ and
>> 41623c91 and compare u-boot.dis.
>
> Your description of the effects of my change is correct. However, this
> raises another question which I would like to see discussed before
> doing anything about these boards.
>
> Taking the last commit where the prefix word was actually emitted (that
> is, 41623c91^, which is actually 60a4f39f, "arm: remove unused _end_vect
> and _vectors_end symbols"), and reading arch/arm/cpu/arm926ejs/start.S,
> I see that the start of the image looks like this:
>
> offset   Content
> +0x0000  prefix word CONFIG_SYS_DV_NOR_BOOT_CFG
> +0x0004  reset vector
> +0x0008  undefined instruction vector
> +0x000c  software interrupt vector
> +0x0010  prefetch abort vector
> +0x0014  data abort vector
> +0x0018  unused
> +0x001c  irq vector
> +0x0020  fiq vector
> +0x0024  (end of vectors table)
>
> And that is /wrong/: the vectors table is misaligned by 4 bytes.
>
> Obviously, the boards have been working fine for a long time, because
> no exception vector was used apparently (or because when exceptions did
> happen, the error was debugged without the need to analyze the
> exception).
>
> I suspect we could just remove the '.word CONFIG_SYS_DV_NOR_BOOT_CFG'
> line from the vectors.S file and prepend the word to the image /after/
> linking.
>
> This, of course, requires confirmation from maintainers.
>
> Manfred, Christian, Sudhakar, Heiko: can any one of you let us know the
> reason for this signature word exactly, and how exactly it is used by
> the board? Ideally, can you also:

See "AM18xx Bootloader Application Report":
http://www.ti.com/lit/pdf/spraba5

Section "3.1 NOR Boot" on page 3ff

This word is used to setup some settings ...

> - test a current build (which does not have the signature word) and
>    confirm it fails to load);
>
> - test the same build with the 4-byte signature manually prepended
>    (this may possibly require padding the image);

I try to find some time for it ...

bye,
Heiko
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