Thanks Siarhei ~! I think it's what Hans's working on, I want to know the debugging instructions of this branch so that I can try with my board.
the uart is combined with sd card, so I can't boot from sd card. On Monday, December 15, 2014 5:28:46 PM UTC+8, Siarhei Siamashka wrote: > > On Sun, 14 Dec 2014 22:01:29 -0800 (PST) > Ricky Xian <szr...@gmail.com <javascript:>> wrote: > > > Hi, > > > > I'm trying to boot from usb fel mode on A23. I have rebuilt your > sunxi-wip > > branch, and try to run on my A23 (q88?) board, but it's failed in fel > mode > > in executing. > > > > I think the u-boot-spl.bin can be used as A20, this's the website I > refer > > to: > > > http://docs.cubieboard.org/tutorials/cb2/development/booting_from_usb_in_fel_mode > > > > > my testing instructions are: > > > > fel write address u-boot-spl.bin > > fel exec address > > > > the address for A20 is 0x2000, so that the DRAM will be initialized. but > > it's incorrect for A23 if the size reach 0x4000. > > > > can you please let me know how to use fel and your u-boot-spl.bin? > > The size 0x4000 is just too large for the SPL binary. You can have a > look at the SRAM memory map that is used in the FEL mode here: > > https://github.com/hno/Allwinner-Info/blob/master/FEL-usb/USB-protocol.txt > > Basically, there are two areas. One starts at 0x2000 and ends somewhere > around 0x5D00 (may be slightly different for different SoC variants). > The stack pointer is set right at the end of this area by the BROM > code before passing control to SPL. So in practice it means that SPL > code, data and stack must all fit there in just ~15K. > > Another free area is around 0x8000-0xbfff, at least on A10/A13/A20. > > The rest of SRAM is used by the BROM code for implementing FEL USB > protocol and we should not touch it. > > In order to provide more room for SPL in the FEL mode, the following > things can be done: > 1) Compile the FEL SPL in Thumb2 mode instead of ARM mode, that's going > to save around 30% of code size (depending on the compiler version). > 2) Take the extra 0x8000-0xbfff area into use. > > I had a patch for this earlier (it is currently self-NAKED): > http://lists.denx.de/pipermail/u-boot/2014-July/183985.html > > Switching to Thumb2 should be perfectly safe. But before using the > 0x8000-0xbfff area, we need to confirm that it is really free to > use on every Allwinner SoC variant and does not clash with the > data structures used by the FEL BROM code. The FEL SRAM memory map > details can be probably clarified by the Allwinner representatives. > > I was kind of reluctant to settle with the Thumb2 part alone until > the sunxi custodians acknowledge that the SPL code size is actually > a real practical problem. For example, this is important for making > other decisions and having some progress with > http://lists.denx.de/pipermail/u-boot/2014-August/185722.html > > To sum it up. Just try to reduce the SPL size. Maybe try a different > gcc version to compile it. Maybe try to apply the Thumb2 tweak. > > -- > Best regards, > Siarhei Siamashka >
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