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

[Marek Vasut]

On 08/02/2016 05:47 PM, Stefan Agner wrote:
> 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...

Isn't the function supposed to flush the whole MMU table ? Or is the
idea here to really flush separate entries ?

> 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();
>>>  }
>>>


-- 
Best regards,
Marek Vasut