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

[Suriyan Ramasami]

Hello Simon, Lukasz,

On Tue, Dec 2, 2014 at 2:29 PM, Lukasz Majewski <l.majewski at majess.pl> wrote:
> Hi Simon,
>
>> Hi,
>>
>> On 28 November 2014 at 06:46, Lukasz Majewski <l.majewski at majess.pl>
>> wrote:
>> > Hello Javier,
>> >
>> >> Hello Lukasz,
>> >>
>> >> On Fri, Nov 28, 2014 at 9:39 AM, Lukasz Majewski
>> >> <l.majewski at majess.pl> wrote:
>> >> >> 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 He or she would like to replace standard (and outdated)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.
>> >> >
>> >>
>> >> I agree with Sjoed that normal users don't replace the low-level
>> >> components that are provided by the board vendor.
>> >>
>> >> After all you can boot a mainline kernel using the vendor u-boot,
>> >> just append the DTB and create a uImage. The practical reason why
>> >> someone would want to replace the vendor u-boot is to have more
>> >> features but is very hard to do if there is a constraint in the
>> >> maximum u-boot image size (even harder if the maximum is such
>> >> small like in the XU3).
>> >
>> > I agree that 328 KiB size for u-boot is a constraint. I don't know
>> > HardKernel's justification for this.
>> >
>> >>
>> >> > 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.
>> >> >
>> >> > It is challenging but for sure doable.
>> >> >
>> >>
>> >> It is doable but I don't see why the default BL2 _must_ be used.
>> >
>> > For practical/pragmatic reasons:
>> >
>> > 1. It is difficult to have signed BL2 - each time we need to ask
>> > HardKernel for signing it. It is impractical and hampers usage of
>> > mainline SPL (BL2) with XU3.
>> >
>> > 2. All the documentation on the HardKernel wiki site refers to the
>> > default BL2.
>> >
>> > 3. We will have "new" BL2, which source code is based on 2012.07
>> > mainline u-boot.
>> >
>> > 4. Two BL2 binaries - IMHO will hurt (i.e. brick) some device sooner
>> > or latter.
>> >
>> >>
>> >> A user that wants to replace the kernel or u-boot is already
>> >> tech-savy and can for sure replace the BL2 as well if it's
>> >> publicly available.
>> >
>> > Sorry, but I'm a bit sceptical about updating such low level code.
>> > Bad things do happen.
>> >
>> >> Maybe hardkernel folks can even make the modified BL2 available on
>> >> their website and the link added in the comment explaining the
>> >> layout?
>> >
>> > We would then require HardKernel to:
>> >
>> > 1. Provide updated BL2.img
>> > 2. Update their wiki to reflect the new BL2.
>> >
>> >>
>> >> Also, it is an artificial constraint after all and can be easily
>> >> modified. In fact I think we should push hardkernel to change that
>> >> layout by default and use a BL2/SPL that has more sensible size for
>> >> the u-boot binary even if they don't need it for their vendor
>> >> u-boot which seems to be quite small.
>> >
>> > I totally agree.
>> >
>> > I'd like to propose a following plan:
>> >
>> > 1. Accept Hyungwon's patches to have XU3 u-boot < 328 KiB (with
>> > link to default BL2) to have XU3 support in place (and treat it as
>> > a starting point)
>> >
>> > 2. If u-boot's size less than 328 KiB is _really_ a problem to
>> > somebody then ask hardkernel to change BL2 or:
>> >         - modify their sources to change the layout (I regard this
>> > as a "quick hack" solution)
>> >         - with a lot of pain develop BL2/SPL (by whom?) which base
>> > on newest mainline (then for each test hardkernel must sign the
>> >           binary).
>>
>> My 2p worth...
>>
>> The current Hardkernel BL1 looks broken to me - it is just too old.
>
> +1
>
>> While it is shipped with the board if you get an eMMC, the main way
>> people will get this is by downloading it from their site. So why not
>> download something different?
>
> As far as I remember U3 and probably XU3 in their README only points
> for HardKernel's site to grab BL1 and BL2. We don't plan to include
> their binaries to u-boot repository.
>
>>
>> Re the plan, I think 1 is fine so long as it is protected by a big
>> ugly hack CONFIG and we can turn it off soon and revert the code.
>
> Hyungwon's patches only touch u-boot and rely (temporary I hope) on BL1
> and BL2/SPL from Hardkernel.
>
>>
>> For 2, the size issue is one problem, but the clock code in U-Boot is
>> another IMO. We should try to get both resolved. Maybe it is possible
>> to use the peach-pit BL2 and get hardkernel to test it and sign it?
>
> I guess that SPL from peach-pit should be tunable to work with XU3 (in
> a finite number of iterations including signing from HardKernel).
>
> As it is based on recent u-boot it should be easy to produce BL2/SPL
> only for XU3 (if needed).
>
>> Then people will download that one instead.
>>
>> is there a contact at hardkernel on the mailing list?
>
> As fair as I know no.
>
> I was posting questions on their forum. Maybe it is a right place to
> ask for contact point?
> As fair as I remember they were willing to sign SPL/BL2 when sent to
> them.
>

I have gotten a BL2 signed (based of their repository) which allows a
bigger U-Boot for testing, and it works. I have currently requested
another signed BL2 which lets one use a 1MB U-Boot image which should
be adequate. This is in the works.
I do not work for hardkernel but I do have a working relationship with
them. From the looks of it they are more than willing to accomodate
this BL2 change.
I can take this action point of getting this BL2 and its related
paraphernalia hosted on their website once they are OK with its
testing.

Regards
- Suriyan

>>
>> Regards,
>> Simon
>
> Best regards,
> Lukasz Majewski
>
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