Le 03/07/2011 09:31, Andreas Bießmann a écrit : > Dear Albert Aribaud, > > Am 03.07.2011 um 08:56 schrieb Albert ARIBAUD: > >> Hi Aneesh, >> >> Le 03/07/2011 06:47, Aneesh V a écrit : >>> Hi Albert, >>> >>> On Saturday 02 July 2011 01:21 AM, Albert ARIBAUD wrote: >>>> Hi Aneesh, >>>> > > <snip> > >>> I was thinking of doing that in start.S itself. I haven't looked at >>> all the details though. >>> >>> BTW, please note that I am not trying to support disjoint BSS in >>> regular u-boot. I think it becomes complex with relocation + it doesn't >>> seem to be worth when all SDRAM is at our disposal. >>> >>> So: >>> 1. #ifdef CONFIG_PRELOADER part in start.s will just pass __bss_start >>> and __bss_end to the clear_bss function(assumes no relocation). >>> 2. #else part of above will assume that bss follows text and data(or at >>> least that __bss_start> _start), so add relocation offset to >>> __bss_start and __bss_end, and pass them to the clear_bss() >>> >>> Does that sound ok? >> >> (note clear_bss is not a function in arch/arm/cpu/armv7/start.S, it is only >> a label) >> >> So, considering what is already in arch/arm/cpu/armv7/start.S, you would >> just add a conditional variant to the BSS clearing code for the preloader >> case? >> >> If so, and considering that you'll pass an offset of 0, why would you need >> that variant for? With offset=0, the code already does what you want, does >> it not? > > we are looking forward to have relocate_code(), clear_bss(), a.s.o. > implemented in c in future (as I understood the discussion around christmas > about relocation). > Wouldn't it be nice to implement now a SPL version of clear_bss(int start, > int size) in c and skip the relocate_code() stuff in start.S completely? > > As I see the normal way to boot is: > > -> some start vector > -> lowlevel_init > -> board_init_f > -> relocate_code > -> board_init_r > > for SPL we do not need the steps after board_init_f. board_init_f > for SPL should implement the generic way to load data from predefined > (compile time) source to predefined target address and branch it. > Therefore a simple memset() in board_init_f could be sufficient to clear > the bss.
Granted, clear_bss could become a function and should be optimized according to the context; however, I don't like the idea of calling a C library function at a point where we know the C environment for the caller is by definition not really set up yet. And as a general rule, I think we should not perform changes 'now for the future' so yes, it would be nice to have a clear_bss() function, but we don't need it right now in U-Boot working as it is now; I'd much prefer the separate clear_bss C function to appear within the patch set that will bring this future general move of relocation to C. > regards > > Andreas Bießmann Amicalement, -- Albert. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
