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  • SRICHARAN R's avatar
    d702b081
    ARM: cache: Move the cp15 CR register read before flushing the cache. · d702b081
    SRICHARAN R authored
    
    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: default avatarR Sricharan <r.sricharan@ti.com>
    d702b081
    History
    ARM: cache: Move the cp15 CR register read before flushing the cache.
    SRICHARAN R authored
    
    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: default avatarR Sricharan <r.sricharan@ti.com>