RFC sunxi: Allwinner A64 SPL support

Hi,

Quoted 34 lines · Hans de Goede

<Adding Peter Robinson to the Cc to see how much he will
object my packaging ideas>

Hi,

First of all cool stuff! Thank you Andre and all others involved for making this happen.

Quoted 12 lines · Alexander Graf

Quoted 11 lines · Andre Przywara

Hi,

this is my first take on the SPL support for the Allwinner A64 SoC. The actual meat - the DRAM initialization code - has been provided by Jens - many thanks for that!
The rest of the patches mostly deal with the 32-bit/64-bit switch.

While it is possible and seems natural to let the SPL also run in 64-bit,
this creates a really large binary (32600 Bytes in my case). With some hacks (plus some fixes to make the SPL 64-bit safe) I got this to work,

Quoted 8 lines

So how about we merge the 64bit version first (since that's *way* easier to compile for everyone) and then consider the move to 32bit afterwards? I don't even want to start to imagine how to squeeze a 32bit SPL build into the build process for our U-Boot binaries.

Quoted 2 lines

but any addition will probably break it and exceed the 32KB limit that the BROM imposes. Debug is the first obvious victim here.

Do you have some section size comparisons between the two?

Later down in the mail Andre says that in 32 bit (thumb) mode the size goes down to 20KB which gives us a lot more head-room then the 32600 out of 32768 bytes available for the 64 bit version.

Quoted 2 lines

With that said I agree with you (Alex) that having a 32 bit SPL + 64 bit u-boot proper is worry-some from a distro pov.

What's even nastier is the requirement of a cross compiler even for a native build. Do Fedora and Suse offer packaged cross-compilers for the other ARM bitness, respectively?