On Thursday 17 March 2011 07:14 PM, Gilles Chanteperdrix wrote: > Aneesh V wrote: >> Hi Gilles, >> >> On Thursday 17 March 2011 06:13 PM, Gilles Chanteperdrix wrote: >>> Hi, >>> >>> I would like to make some changes to u-boot on pandaboard. Sometimes in >>> the past, in u-boot, I could "loadb" a new u-boot binary, then "go" to >>> it, and the new version of u-boot would start. This was far from >>> perfect, but it made testing small changes possible. This also works >>> with the version of u-boot provided on the pandaboard community site. >>> >>> The magic which made this possible was in the "start.S" file, I see that >>> the code changed, but there still seems to be a relocation (somewhat >>> more complicated, since it handles ELF relocations), so it seems it >>> should work. >>> >>> So my question is: is this "loadb+go" method still supposed to be >>> working, and only broken, somehow, on pandaboard? Or is it no longer >>> supposed to be working? >> >> Couple of things you might want to consider. >> * According to the new relocation scheme u-boot should start running >> from the address that it is linked to. You must load it to >> CONFIG_SYS_TEXT_BASE > > You mean the address where u-boot is currently loaded? But that will not > work, right? I mean, it would override the current u-boot while it is > currently running. > > I do not really understand this answer, what does it mean? The > relocation code does not work if the address it is starting from is not > CONFIG_SYS_TEXT_BASE? What if I reinsert the memcpy in start.S which > copies to CONFIG_SYS_TEXT_BASE?
Here is my understanding: Eearlier the memcpy was done very early in start.S(before board_init_f) and everything until that point was position independent. Copy was done *to* CONFIG_SYS_TEXT_BASE Now, this memcpy has been removed and we assume that we start from CONFIG_SYS_TEXT_BASE. After board_init_f we copy the image *from* CONFIG_SYS_TEXT_BASE to the end of available memory and do ELF relocation. board_init_f will crash unless you are running from CONFIG_SYS_TEXT_BASE Since U-Boot is relocated to the end of available memory you will not likely over-write existing U-Boot if you copy to CONFIG_SYS_TEXT_BASE, certainly not on Panda with 1GB memory. Re-inserting the memcpy may not be necessary I believe. > >> * Data cache enabled in U-Boot could be a problem. You will end up >> having cache coherency issues unless you flush the caches after loadb. >> Better keep them disabled using CONFIG_SYS_NO_DCACHE > > Ok, that is not really an issue for development. > _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
