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

[Hans de Goede]

Hi,

On 02-03-15 12:51, Vishnu Patekar wrote:
> 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?

IANAL, but linking non GPL binaries into a GPL binary is not good.
But in the end it does not matter even if Allwinnner does not honor
the GPL, we must still honor their copyrights, this are 2 orthogonal
(independent) issues.

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

Thanks!

Regards,

Hans