[U-Boot] [PATCH] arm: cache: always flush cache line size for page table

[Stefan Agner]

On 2016-08-02 02:38, Marek Vasut wrote:
> On 08/02/2016 09:07 AM, Stefan Agner wrote:
>> From: Stefan Agner <stefan.agner at toradex.com>
>>
>> The page table is maintained by the CPU, hence it is safe to always
>> align cache flush to a whole cache line size. This allows to use
>> mmu_page_table_flush for a single page table, e.g. when configure
>> only small regions through mmu_set_region_dcache_behaviour.
>>
>> Signed-off-by: Stefan Agner <stefan.agner at toradex.com>
>> ---
>> This avoids two messages observed on a i.MX 7 based system:
>> CACHE: Misaligned operation at range [9fff0000, 9fff0004]
>> CACHE: Misaligned operation at range [9fff0024, 9fff0028]
>>
>> Those were caused by two calls to mmu_set_region_dcache_behaviour
>> in arch/arm/imx-common/cache.c (enable_caches).
>>
>> Not sure if this is the right way to fix this... Also, we could
>> do the alignment in mmu_set_region_dcache_behaviour.
> 
> This should be fixed on the driver level indeed, not in cache_v7.c

Fixing it in enable_caches in arch/arm/imx-common/cache.c is definitely
unpractical...

So I guess by driver level you mean in 
arch/arm/lib/cache-cp15.c:mmu_set_region_dcache_behaviour
correct?

It has the potential to code duplication in case other users of
mmu_page_table_flush need to flush page tables less than cache line
size...

I felt that mmu_page_table_flush is a convenience function and should
take care of that issue.

--
Stefan



> 
>> --
>> Stefan
>>
>>  arch/arm/cpu/armv7/cache_v7.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/arch/arm/cpu/armv7/cache_v7.c b/arch/arm/cpu/armv7/cache_v7.c
>> index 52f1856..71787fc 100644
>> --- a/arch/arm/cpu/armv7/cache_v7.c
>> +++ b/arch/arm/cpu/armv7/cache_v7.c
>> @@ -147,6 +147,13 @@ void arm_init_before_mmu(void)
>>
>>  void mmu_page_table_flush(unsigned long start, unsigned long stop)
>>  {
>> +	/*
>> +	 * Make sure range is cache line aligned
>> +	 * Only CPU maintains page tables, hence it is save to always
>> +	 * flush the complete cache line...
>> +	 */
>> +	start &= ~(CONFIG_SYS_CACHELINE_SIZE - 1);
>> +	stop = ALIGN(stop, CONFIG_SYS_CACHELINE_SIZE);
>>  	flush_dcache_range(start, stop);
>>  	v7_inval_tlb();
>>  }
>>