[U-Boot] MIPS cpu has problem detecting CFI

[myuboot at fastmail.fm <myuboot@fastmail.fm>]

I think I found a problem in cpu/mips/start.S.

gp register is used to point to the SDRAM. But after gp is adjusted to
proper location, a C function flush_cache is called. But this function
actually changes gp register before gp is used to jump to SDRAM. That
makes the u-boot run from flash and fails to detect CFI.

Here is the assembler code for flush_cache.c
(gdb) disassem 0xb0000798
Dump of assembler code for function flush_cache:
0xb000078c <flush_cache+0>:     lui     gp,0x3
0xb0000790 <flush_cache+4>:     addiu   gp,gp,-32300
0xb0000794 <flush_cache+8>:     addu    gp,gp,t9

And here is how I fixed the issue -


diff --git a/u-boot-2009.08/cpu/mips/start.S
b/u-boot-2009.08/cpu/mips/start.S
index 57db589..0e8f8ed 100644
--- a/u-boot-2009.08/cpu/mips/start.S
+++ b/u-boot-2009.08/cpu/mips/start.S
@@ -321,6 +321,7 @@ relocate_code:
        move    t6, gp
        sub     gp, CONFIG_SYS_MONITOR_BASE
        add     gp, a2          /* gp now adjusted              */
+        move    t8, gp
        sub     s1, gp, t6      /* s1 <-- relocation offset     */

        /*
@@ -358,6 +359,7 @@ relocate_code:

        /* Jump to where we've relocated ourselves.
         */
+        move    gp, t8
        addi    t0, s2, in_ram - _start
        jr      t0
        nop