Hello Hans,
Thank you for the comments.
On Mon, Mar 2, 2015 at 3:55 PM, Hans de Goede <[email protected]> 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.
