ARM: implement relocation for ARM926

Change the implementation for arm926 to relocate the code to
an arbitrary address in RAM.

Adapt the TX25 (i.MX25), magnesium board to test the changes.

On the tx25 board TEXT_BASE is set to the final relocation
address to prevent one more copying of u-boot code
when relocating. More info see:
doc/README.arm-relocation

da850 board:
Tested-by: Ben Gardiner <bengardiner@nanometrics.ca>

Portions of this work were supported by funding from
the CE Linux Forum.

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Ben Gardiner <bengardiner@nanometrics.ca>

1 files changed, 23 insertions, 0 deletions

diff --git a/doc/README.arm-relocation b/doc/README.arm-relocation
index 6be1a12923..e3ed60ecdc 100644
--- a/doc/README.arm-relocation
+++ b/doc/README.arm-relocation
@@ -43,6 +43,29 @@ CONFIG_SYS_ARM_WITHOUT_RELOC defined!!!
 
 -------------------------------------------------------------------------------------
 
+For boards which boot from nand_spl, it is possible to save a copy
+if TEXT_BASE == relocation address! This prevents that uboot code
+is copied again in relocate_code().
+
+example for the tx25 board:
+
+a) cpu starts
+b) it copies the first page in nand to internal ram
+   (nand_spl_code)
+c) end executes this code
+d) this initialize CPU, RAM, ... and copy itself to RAM
+   (this bin must fit in one page, so board_init_f()
+    don;t fit in it ... )
+e) there it copy u-boot to CONFIG_SYS_NAND_U_BOOT_DST and
+   starts this image @ CONFIG_SYS_NAND_U_BOOT_START
+f) u-boot code steps through board_init_f() and calculates
+   the relocation address and copy itself to it
+
+If TEXT_BASE == relocation address, the copying of u-boot
+in f) could be saved.
+
+-------------------------------------------------------------------------------------
+
 ToDo:
 
 - fill in bd_t infos (check)