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authorJoakim Tjernlund <Joakim.Tjernlund@transmode.se>2010-01-19 14:41:58 +0100
committerWolfgang Denk <wd@denx.de>2010-01-26 19:30:15 +0100
commite6bee80814c3a0d7eab89d28142fe68c4a670f31 (patch)
tree78622a77e356e93dd3fed7c4728b776358c7b2f0 /README
parent0f8aa159175385ddd77bc91d11b9568583fbbd0c (diff)
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ppc: Update README about the new GOT ptr.
r14 is no longer used as non volatile GOT ptr. Instead the volatile r12 is used so be sure to do GET_GOT in asm code when you need to access global data. Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Diffstat (limited to 'README')
-rw-r--r--README4
1 files changed, 3 insertions, 1 deletions
diff --git a/README b/README
index 7affe10..263bb05 100644
--- a/README
+++ b/README
@@ -3922,7 +3922,9 @@ For PowerPC, the following registers have specific use:
R30: GOT pointer
R31: frame pointer
- (U-Boot also uses R14 as internal GOT pointer.)
+ (U-Boot also uses R12 as internal GOT pointer. r12
+ is a volatile register so r12 needs to be reset when
+ going back and forth between asm and C)
==> U-Boot will use R2 to hold a pointer to the global data