[U-Boot] [PATCH v9 2/2] Odroid-XU3: Add documentation for Odroid-XU3

[Lukasz Majewski <l.majewski@majess.pl>]

Hi Sjoerd,

> On Fri, 2014-11-28 at 09:39 +0100, Lukasz Majewski wrote:
> > Hi Sjoerd,
> > 
> > > On Fri, 2014-11-28 at 13:45 +0900, Hyungwon Hwang wrote:
> > > > On Thu, 27 Nov 2014 15:33:05 +0100
> > > > Sjoerd Simons <sjoerd.simons@collabora.co.uk> wrote:
> > > 
> > > > > signed_bl1_position=1
> > > > > bl2_position=31
> > > > > uboot_position=63
> > > > > tzsw_position=719
> > > > > env_position=1231
> > > > > 
> > > > > for the various locations.. Which also explains the limit
> > > > > 335872 bytes in your initial mail.. Awkward one though.
> > > > > Wonder if that's an SoC issue or something hardkernel could
> > > > > fix by having a different bl1/bl2?
> > > > > 
> > > > 
> > > > (719 - 63) * 512 = 335876 bytes. The limitation is needed not to
> > > > overwrite tzsw.
> > > > 
> > > > Are you saying that the limitation can be removed? Yes, with
> > > > different bl1/bl2. But I do not think that another bl1/bl2 will
> > > > be released to relieve the limitation.
> > > 
> > > It was a something i was wondering. After send this e-mail i had a
> > > chat with Mauro Ribeiro on #linux-exynos. He indicate that the BL2
> > > determines the u-boot load location and that it's an u-boot SPL
> > > build from their u-boot branch. Also he indicated that he would
> > > be happy to sign a modified SPL build which e.g. loads u-boot
> > > from behind the TZSW.
> > > 
> > > You can find the IRC log here:
> > > http://irclog.whitequark.org/linux-exynos/2014-11-27
> > > 
> > > I have yet to take him up on that offer though, but it sounds
> > > like a good way forward. The current layout really isn't
> > > practical.
> > > 
> > 
> > It indeed isn't very practical, but this is what you received from
> > HardKernel when you buy XU3 board.
> > 
> > Of course you can grab their sources, modify the layout, prepare
> > u-boot's SPL and send it to them to be signed.
> > However, it is not the way the "normal" user do things.
> > 
> > He or she would like to replace standard (and outdated) HardKernel
> > u-boot on their SD card and go forward with booting kernel.
> 
> > For now we _must_ focus on supporting XU3 with default BL1/BL2 and
> > hence we are obliged to have u-boot size smaller than 328 KiB.
> 
> I don't see a big issue with telling the "normal" user[0] to replace
> both the BL2 and u-boot itself. If the hardkernel folks indeed do sign
> the BL2 for us, i'm more then happy to make that publically available.
> 

I just would like to avoid having two incompatible BL2s floating
around.

Does your use case require u-boot size larger than 328 KiB?
Hyungwon has managed to provide functional one with size less than 328
KiB.

Another issue is the exact SPL source code from which you would like to
build BL2 with modified layout.

Do you plan to use HardKernel's source code and only modify the layout
or use SPL from cutting edge mainline?

Please note that even for tests BL2 must be signed by HardKernel to
cooperate with Samsung's proprietary BL1.

> 
> 0: Do normal users replace u-boot?
> 

I know a few developers who did this because they needed new features
missing in HardKernel's version (like UMS support).

Best regards,
Lukasz Majewski
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