When building the mxs platform in thumb mode gcc generates code using
the intra procedure call scratch register (ip/r12) for the calling the
lowlevel_init function. This modifies the lr in flush_dcache which
causes u-boot proper to end in an endless loop.
40002334: e1a0c00e mov ip, lr
40002338: eb00df4c bl 4003a070
<__lowlevel_init_from_arm>
4000233c: e1a0e00c mov lr, ip
40002340: e1a0f00e mov pc, lr
[...]
4003a070 <__lowlevel_init_from_arm>:
4003a070: e59fc004 ldr ip, [pc, #4] ; 4003a07c
<__lowlevel_init_from_arm+0xc>
4003a074: e08fc00c add ip, pc, ip
4003a078: e12fff1c bx ip
4003a07c: fffc86cd .word 0xfffc86cd
Instead of using the the ip/r12 register we use sl/r10 to preserve the
link register.
According to "Procedure Call Standard for the ARM Architecture" by ARM
subroutines have to preserve the contents of register r4-r8, r10, r11
and SP. So using r10 instead of r12 should be save.
Signed-off-by: Klaus Goger <klaus.go...@theobroma-systems.com>
Signed-off-by: Christoph Muellner <christoph.muell...@theobroma-systems.com>
---
Changes in v2:
- use bl instead of blx to call lowlevel_init
- remove mxs tag as it apply to all arm926ejs platforms
arch/arm/cpu/arm926ejs/start.S | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm/cpu/arm926ejs/start.S b/arch/arm/cpu/arm926ejs/start.S
index 959d1ed86d..317df5c401 100644
--- a/arch/arm/cpu/arm926ejs/start.S
+++ b/arch/arm/cpu/arm926ejs/start.S
@@ -105,9 +105,9 @@ flush_dcache:
/*
* Go setup Memory and board specific bits prior to relocation.
*/
- mov ip, lr /* perserve link reg across call */
+ mov sl, lr /* perserve link reg across call */
bl lowlevel_init /* go setup pll,mux,memory */
- mov lr, ip /* restore link */
+ mov lr, sl /* restore link */
#endif
- mov pc, lr /* back to my caller */
+ bx lr /* back to my caller */
#endif /* CONFIG_SKIP_LOWLEVEL_INIT */
--
2.11.0
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