Le 01/11/2010 20:44, Graeme Russ a écrit :
On Tuesday, November 2, 2010, Albert ARIBAUDalbert.aribaud@free.fr wrote:
Le 01/11/2010 20:23, Wolfgang Denk a écrit :
Dear Albert ARIBAUD,
In message4CCEF2E4.5080003@free.fr you wrote:
Also, I understand why the second RFC change I did was harmful to tx25. Contrary to u-boot itself, u-boot-spl is not compiled to be position independent; it actually loads at a given address then copies itself, without relocating, to its home location.
It copies _itself_? Not the U-Boot payload?
Heiko, is this intentional? Do we really first load the whole image, then copy the U-Boot payload to some other address, then relocate it to yet another one?
I haven't been clear.
The boot ROM or IPL loads u-boot-spl in RAM at a fixed location and jumps to it.
u-boot-spl copies itself at its intended location if not already there, and jumps to tiself at that new location.
u-boot-spl loads u-boot at a fixed location and jumps to it.
u-boot relocates (copies and fixes up) itself at top of ram if not already there, and jumps to itself at that new location.
Wow, what a terrible waste!
Why does u-boot-spl need to relocate?
As I said, u-boot-spl does not relocate, it only copies itself to its link-time location and jumps there, and it does this only if loaded somewhere else to boot (if I may say so). *Usually* it will be loaded at the right place and thus won't copy itself and jump to itself.
It still takes up some space, though. The copy and jump could actually be #ifdef's on CONFIG_NAND_SPL if everyone thinks it is safe -- please comment quickly as I'm preparing a patch set and that could go in it if agreed to.
Can't u-boot-spl load AND relocate u-boot, or does u-boot-spl have tight space constraints?
It has; it comes from a (usually small) NAND page.
Regards
Graeme
Amicalement,