[U-Boot] Basic A33 support including dram init available in my personal repo

[Hans de Goede]

Hi,

On 01-03-15 19:42, Vishnu Patekar wrote:
> Allwinner A33 tablets comes with the libdram binary, fortunately I've
> found the libdram code at
> https://github.com/realthunder/a33_bootloader/tree/master/basic_loader/bsp/bsp_for_a67.

Ah, that is both good and bad...

> I've integrated it with mainline u-boot, still lot to do to post it to upstream

Integrated sounds as if you've copied pieces of code from the bsp code you've found
into mainline u-boot. That is a big no no (this the bad part). AFAIK the bsp code
does not come with a GPL license header, and Allwinner does not want to release
these bits under the GPL for whatever reasons, a lot can be said about this, but
in the end currently the bsp code is not GPL licensed, so we cannot use it / copy
from it. There can be no discussion on this, when you're submitting this upstream
you must not have any literal copied code in the patch you're sending upstream.

You can use non copyrightable information from the bsp sources like register
names and the initialization algorithm (IANAL), but you must 100% write your own
code!

I've been working on A33 dram support too, without any source code access, instead
I've been tracing what the boot0 machine code does and going from there. What I've
sofar is that the code first inits the DRAM PLL / cmu dram registers, it seems that
the A33 has 2 dram pll-s and that one of the dram_para fields configures which pll
to use and configures some sigma-delta pattern to reduce rf interference, at least
on my A33 tablet the code seems to want to pick the new / second dram pll. But I
see no reason why the first one should not work, so for now if I were you I would
just use the A23 dram pll / cmu setup code modified to set the one or 2 extra
reset / enable bits the A33 has, but still using the old / first dram pll, we can
always add support for the new one later.

Then the boot0 code calculates a load of timing parameters and writes these to
registers. I've already written my own C-code reproducing the init algorithm from
boot0 for this (attached) this is GPL code and you should be able to use this to
replace a chunk of the bsp code. Note that I found 2 code paths based on a tpr13
bit (iirc) one for autoconfig, and one for reading values from the tpr dram_para
values, my code supports only autoconfig, you can add a printf to warn if manual
config is requested and still keep using autoconfig. The same goes for any other
code paths were there is both a manual and an auto option, look at what actual
shipped tablets are using, only support that and print a warning for the other
case, were possible always use autoconfig.

After this boot0 does more stuff, but this is as far as I've gotten and
currently I've other priorities.

If I were you I would start with the existing dram_sun6i.c from
upstream u-boot, as the A33 DRAM controller seems to be closest to the
A31 one, then add in the dram_sun8i.c pll init code, and the timing
stuff which I've already written, and then see where the initialization
algorithm is different for the A33 and modify the dram_sun6i.c code to
match what is needed to get the A33 going, if extra code is needed you
MUST write NEW code.

When you submit support for this upstream you must include a Signed-off-by,
and thereby you are declaring that the code is all your own and that you've
the right to submit this code under the GPL license, this means that there
must be absolutely no copied code in your upstream patch submission!

Also see:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/SubmittingPatches

Section "11) Sign your work

> Basic A33 support including dram init available in my personal repo
> https://github.com/vishnupatekar/u-boot-sunxi/tree/a33-dram
>
> I could able to boot u-boot over fel, and get u-boot command prompt on
> microSD pins which are multiplexed with UART0.
>
> The device page for A33 tablet which I've is here:
> http://linux-sunxi.org/Softwinner_astar-rda

Thanks for your work on this, and sorry if I sound a bit harsh above, but I
really need to be strict about not allowing any non GPL code into u-boot.

Regards,

Hans
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