Re: [PATCH 2/3] ARM: socfpga: add support for Enclustra AA1

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hi,

On 07.07.22 12:57, Ahmad Fatoum wrote:
> On 07.07.22 12:41, Steffen Trumtrar wrote:
>> Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>

[snip]

>> +static noinline void aa1_start(void)
>> +{
>> +	int pbl_index = 0;
>> +	int barebox = 0;
>> +	int bitstream = 0;
>> +
>> +	arm_early_mmu_cache_invalidate();
> 
> Is this really required? If MMU is enabled by the time you
> enter here, you risk executing garbage before hitting
> this line anyway and if it's disabled, caches will be invalidated
> just before MMU is enabled already.
> 
>> +
>> +	relocate_to_current_adr();

I see now that I was mistaken here, because relocate_to_current_adr()
called directly after will call sync_for_execution(), which will clean
D$ and invalidate I$. If we happen to have stale dirty D$ entries,
these will be flushed and corrupt memory, which
arm_early_mmu_cache_invalidate() avoided. I still think we shouldn't
expect board code to call arm_early_mmu_cache_invalidate(), rather
sync_caches_for_execution() should take care to only invalidate I$,
when caches are disabled.

My "ARM: sync_caches_for_execution: don't flush disabled data cache"
patch from earlier today should resolve this. You'll probably want
to cherry pick it..

Cheers,
Ahmad


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