Hi Rogan, Le 20/04/2011 09:46, Rogan Dawes a écrit : > On 2011/04/20 7:42 AM, Albert ARIBAUD wrote: >> Le 20/04/2011 04:23, Hebbar, Gururaja a écrit : >>> Hi, >>> >>> On Wed, Apr 20, 2011 at 02:43:23, Rogan Dawes wrote: >>>> Hi folks, >>>> >>>> I'm trying to understand a bit more about how u-boot creates the >>>> image, such that the CPU reset vector is pointing to the right piece >>>> of code when it is reset. >>>> >>>> i.e. my DNS323 (Orion5x) has a reset vector of 0xffff0000. But for >>>> the life of me, I can't find anywhere that actually references that >>>> value to place the start code at that point. >>>> >>> >>> Placing the final boot image is left to user who flashes/burns it >>> board. But it should be same as _TEXT_BASE (this is being removed now. >>> Orion5x is arm based). Also look >>> at<u-boot-src>\arch\arm\cpu\arm926ejs\start.S& >>> <u-boot-src>\arch\arm\cpu\arm926ejs\u-boot.lds for more info on how >>> linker is instructed to place the starting code at predefined address. >>> >>>> I'm basically trying to make sure that my CONFIG_SYS_TEXT_BASE is >>>> correct (the address in the flash to which I write the whole >>>> u-boot.bin file, right?. >>>> >>> This is passed to linker as the entry point. >> >> There is another point re: orion5x based boards: often, their designers >> preferred generating a linear image for U-Boot, but the fact that the >> vector address is at FFFF0000 makes it impossible to directly the image >> there because it is always greater than 64K. So the designers put some >> "pseudo-rom boot code" at FFFF0000 that will finally jump to an address >> lower in FLASH; for ED Mini V2 it is FFF90000, and that's where the >> U-Boot image is supposed to be flashed. > > So, is that the address that you would use for CONFIG_SYS_TEXT_BASE ?
Yes, exactly. >> Rogan, I bet in the DNS323 case, the same applies modulo your Flash >> size. Try tracing through the FFFF0000 code, it should not last more >> than a few tens of instructions before it jumps to some absolute address. > > Do you think it would be possible to figure it out from the original > vendor u-boot? Sort of: if you look up the vendor U-Boot source code and find nothing about 0xFFFF0000, that's a sign that it expects something else than U-Boot to kick in at that address. You can also disassemble what lies at 0xFFFF0000 on your board, either live through JTAG or offline by running a binary extract of FFFF0000 through objdump. > Thanks > > Rogan Amicalement, -- Albert. _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
