[U-Boot] Linking some code to internal SRAM instead of SDRAM

[Alexander Stein]

Hello,

I have an at91 based board which starts from NOR flash. I have an ugly 
workaround in lowlevel_init.S that switching from slowclock to PLLA is done 
from the internal SRAM instead directly from NOR which is not possible as the 
NOR flash timing are also affected. So i copied some data around using 
existing an new labels.
A new approach would be to link lowlevel_init directly at 0x00200000 (which is 
AT91SAM9260_SRAM0_BASE) but the code is located next to the "normal" .text 
segment. I've prepared a change to cpu/arm926ejs/u-boot.lds (I know it's still 
2010.3 but that shouldn't matter now) which links lowlevel_init to 0x00200000. 
I added the symbols __lowlevel_init_start and __lowlevel_init_end to be used 
to copy the function from it's LMA to it's VMA address.
I'm rather unsure if this will work as I thought, Of course more has to be 
done, like 
* Make SRAM address configureable
* Only link to this if CONFIG_SKIP_LOWLEVEL_INIT is not defined
* Maybe create a region for that
* ...
Any opinions, hints, more elegant methods? 

diff --git a/cpu/arm926ejs/u-boot.lds b/cpu/arm926ejs/u-boot.lds
index ee5eeb5..c368822 100644
--- a/cpu/arm926ejs/u-boot.lds
+++ b/cpu/arm926ejs/u-boot.lds
@@ -32,9 +32,16 @@ SECTIONS
	.text :
	{
		cpu/arm926ejs/start.o   (.text)
+		*(EXCLUDE_FILE(*lowlevel_init.o) .text)
+	}
+	__lowlevel_init_start = .;
+	.lowlevel_init 0x00200000 : AT ( ADDR (.text) + SIZEOF (.text) )
+	{
		*(.text)
	}
+	__lowlevel_init_end = .;

+	. = ADDR (.text) + SIZEOF (.text) + SIZEOF(.lowlevel_init);
	. = ALIGN(4);
	.rodata : { *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*))) }


Best regards
Alexander