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

[Vishnu Patekar]

Hello Hans,
Thank you for the comments.

On Mon, Mar 2, 2015 at 3:55 PM, Hans de Goede <hdegoede at redhat.com> wrote:

> 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...

Now, for me good part is over, now it's just 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.
>

No, You've not been harsh, instead you've been helpful in this case.

Thank you for clearing my doubts. I was under impression that if we keep
the copyright header, it can be accepted.

BTW, libdram as binary and used in u-boot is also GPL violation, right?

I'll see how can I re-use the A31 dram init code and get it work for A33.


>
> Regards,
>
> Hans
>