[PATCH v1 07/14] powerpc: mpc83xx: Don't activate MMU when not necessary

[Christophe Leroy]

At startup, some RAM is needed (for instance for stack) before
DRAM is initialised.

One way to offer such RAM, used by mpc83xx, is to lock some entries
in the cache. To do that, MMU needs to be activated.

On mpc83xx having a QUICC Engine an alternative is to user some
part of from the Multi User RAM, like done on mpc8xx for instance.
For that, the MMU is not needed.

Activating the MMU is problematic because exception vectors are not
setup yet so in case of ISI or DSI that CPU will crash and reboot.

At the time being, MMU is activated regardless.

Only activate it when locking cache entries to provide initial RAM.

Signed-off-by: Christophe Leroy <christophe.leroy at csgroup.eu>
---
 arch/powerpc/cpu/mpc83xx/start.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/cpu/mpc83xx/start.S b/arch/powerpc/cpu/mpc83xx/start.S
index 4329b173db..6749263da8 100644
--- a/arch/powerpc/cpu/mpc83xx/start.S
+++ b/arch/powerpc/cpu/mpc83xx/start.S
@@ -215,6 +215,7 @@ in_flash:
 	 * gt-regs BAT can be reused after board_init_f calls
 	 * board_early_init_f (EVB only).
 	 */
+#ifdef CONFIG_SYS_INIT_RAM_LOCK
 	/* enable address translation */
 	bl	enable_addr_trans
 	sync
@@ -222,7 +223,6 @@ in_flash:
 	/* enable the data cache */
 	bl	dcache_enable
 	sync
-#ifdef CONFIG_SYS_INIT_RAM_LOCK
 	bl	lock_ram_in_cache
 	sync
 #endif
-- 
2.39.2