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ARM: cache: Move the cp15 CR register read before flushing the cache.

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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>
This commit is contained in:
SRICHARAN R 2012-05-16 23:52:54 +00:00 committed by Albert ARIBAUD
parent d519b4bc0a
commit d702b0811d
1 changed files with 3 additions and 3 deletions
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6
arch/arm/lib/cache-cp15.c
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@ -115,17 +115,17 @@ static void cache_disable(uint32_t cache_bit)
{
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