ARM: cache: Move the cp15 CR register read before flushing the cache.
The following is the cleanup sequence in arch/arm/cpu/armv7/cpu.c
int cleanup_before_linux(void)
{
...
...
dcache_disable();
v7_outer_cache_disable();
invalidate_dcache_all();
}
1) invalidate_dcache_all call expects that all the caches has been
flushed, invalidated and there are no dirty entries prior to its
execution. In the above sequence dcache_disable() flushes, invalidates
the caches and turns off the mmu. But after it cleanups the cache
and before the mmu is disabled there is a cp_delay() function which
has STR instruction. On certain cores like the cortex-a15, cache hit
and a write can happen to a cache line even when the dcache is
disabled. So the above mentioned STR instruction creates a dirty entry
after cleaning. The mmu gets disabled after this.
2) invalidate_dcache_all invalidates the cache lines. Again on
cores like cortex-a15, invalidate instruction flushes the dirty
line as well. So some times the dirty line from sequence 1
can corrupt the memory resulting in a crash.
Fixing this by moving the get_cr() and cp_delay() calls before
cleaning up the cache, thus avoiding the dirty entry.
Signed-off-by: R Sricharan <r.sricharan@ti.com>
diff --git a/arch/arm/lib/cache-cp15.c b/arch/arm/lib/cache-cp15.c
index e6c3eae..939de10 100644
--- a/arch/arm/lib/cache-cp15.c
+++ b/arch/arm/lib/cache-cp15.c
@@ -115,17 +115,17 @@
{
uint32_t reg;
+ reg = get_cr();
+ cp_delay();
+
if (cache_bit == CR_C) {
/* if cache isn;t enabled no need to disable */
- reg = get_cr();
if ((reg & CR_C) != CR_C)
return;
/* if disabling data cache, disable mmu too */
cache_bit |= CR_M;
flush_dcache_all();
}
- reg = get_cr();
- cp_delay();
set_cr(reg & ~cache_bit);
}
#endif