On Tue, Oct 5, 2010 at 4:40 PM, Graeme Russ graeme.russ@gmail.com wrote:
On Tue, Oct 5, 2010 at 4:34 PM, Wolfgang Denk wd@denx.de wrote:
Dear Graeme Russ,
In message AANLkTikqE0_DEqHs-tX3A4XuEXJhM0CYW_+j6izhmktw@mail.gmail.com you wrote:
Can NAND SPL initialise and size memory before loading U-Boot into RAM?
It has to. You cannot load into and run from uninitialized RAM ;-)
If so, could the relocation code be added to NAND SPL so only one copy operation is performed?
I'm afraid it cannot, due to size limitations. The NAND loader often hast to fit into as little a 2 or 4 KiB...
For x86, the actual relocation calculations can be done in a probably a few dozen bytes of code. It contains:
- One offset calculation
- A single tight loop
- Two comparisons (probably not needed in the generic case as they are used
to filter out x86 specific code outside .text)
- An offset addition
If the only constraint is space then it _may_ be possible in some scenarios (although I do acknowledge that previous trival changes have caused the size constaint to be violated)
Another alternative is to load into upper memory and have the relocation code detect that U-Boot is already there and skip the copy operation
Regards,
Graeme