[U-Boot] SoCFPGA PL330 DMA driver and ECC scrubbing

[Marek Vasut]

On 07/11/2018 07:30 PM, Trent Piepho wrote:
> On Wed, 2018-07-11 at 08:56 -0500, Jason Rush wrote:
>> On 7/11/2018 8:48 AM, Marek Vasut wrote:
>>> On 07/11/2018 03:49 PM, Jason Rush wrote:
>>>>
>>>> My mistake.  I did disable the dcache after scrubbing too.  The
>>>> code is almost identical to the Arria10 code where after
>>>> scrubbing it flushes the dcache, then turns it off.
>>>>
>>>> The weird reset problems happens if I scrub the area where
>>>> u-boot relocates to with the dcache on, then turn dcache off.
>>>>
>>>> I tried to also tried turning the MMU off, but that didn't help.
>>>
>>> Maybe there are some data used by the SPL there ? I think the SPL has
>>> malloc area in RAM at some point.
>>>
>>
>> I thought something similar, so I narrowed it down to clearing
>> just from where U-Boot relocates to the end of DRAM.  If I'm
>> correct, that includes where U-Boot relocates and where the
>> MMU tables are normally stored.
> 
> I wonder if the reset does not properly reset the CPU caches?  The idea
> being that the CPU cache has stale data from before the reset, or maybe
> just stale tag bits, and the hang is due to using this bad data from
> the cache.

That's why we do dcache_off() icache_off() first, to make sure the
caches are in consistent state. But a good point nonetheless, this
should be checked.

> Or perhaps there is always something done incorrectly, but it is only
> the state of DRAM after a reset, vs a power cycle, that consistently
> triggers a hang?

The SoCFPGA has some weird warm/cold reset hooks even in the bootrom,
could be. But the DRAM should be torn down in either case.

> If possible, try to add code before the hang point to invalidate both
> the i-cache and d-cache for the problem region above.  Perhaps the SPL
> is doing something wrong w.r.t. cache invalidation, e.g. moving code
> around and not updating the i-cache, because it assumes nothing has yet
> used the caches, which is now no longer the case since you turn them on
> for scrubbing.
> 


-- 
Best regards,
Marek Vasut