Hello Hans, Thank you for the comments.
On Mon, Mar 2, 2015 at 3:55 PM, Hans de Goede hdegoede@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