[MIPS] Request for the 'mips_cache_lock()' removal
The initial intension of having mips_cache_lock() was to use the cache
as memory for temporary stack use so that a C environment can be set up
as early as possible.
But now mips_cache_lock() follow lowlevel_init(). We've already have the
real memory initilaized at this point, therefore we could/should use it.
No reason to lock at all.
Other problems:
Cache locking is not consistent across MIPS implementaions. Some imple-
mentations don't support locking at all. The style of locking varies -
some support per line locking, others per way, etc. Some parts use bits
in status registers instead of cache ops. Current mips_cache_lock() is
not necessarily general-purpose.
And this is worthy of special mention; once U-Boot/MIPS locks the lines,
they are never get unlocked, so the code relies on whatever gets loaded
after U-Boot to re-initialize the cache and clear the locks. We're sup-
posed to have CFG_INIT_RAM_LOCK and unlock_ram_in_cache() implemented,
but leave the situation as it is for a long time.
For these reasons, I proposed the removal of mips_cache_lock() from the
global start-up code.
This patch adds CFG_INIT_RAM_LOCK_MIPS to make existing users aware that
*things have changed*. If he wants the same behavior as before, he needs
to have CFG_INIT_RAM_LOCK_MIPS in his config file.
If we don't have any regression report through several releases, then
we'll remove codes entirely.
Signed-off-by: Shinya Kuribayashi <skuribay@ruby.dti.ne.jp>
Acked-by: Andrew Dyer <amdyer@gmail.com>
diff --git a/cpu/mips/cache.S b/cpu/mips/cache.S
index 443240e..67ee19f 100644
--- a/cpu/mips/cache.S
+++ b/cpu/mips/cache.S
@@ -238,6 +238,7 @@
.end dcache_disable
+#ifdef CFG_INIT_RAM_LOCK_MIPS
/*******************************************************************************
*
* mips_cache_lock - lock RAM area pointed to by a0 in cache.
@@ -263,3 +264,4 @@
j ra
.end mips_cache_lock
+#endif /* CFG_INIT_RAM_LOCK_MIPS */
diff --git a/cpu/mips/start.S b/cpu/mips/start.S
index c92b162..930f9b3 100644
--- a/cpu/mips/start.S
+++ b/cpu/mips/start.S
@@ -267,10 +267,12 @@
/* Set up temporary stack.
*/
+#ifdef CFG_INIT_RAM_LOCK_MIPS
li a0, CFG_INIT_SP_OFFSET
la t9, mips_cache_lock
jalr t9
nop
+#endif
li t0, CFG_SDRAM_BASE + CFG_INIT_SP_OFFSET
la sp, 0(t0)