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

[Jason Rush]

On 7/11/2018 1:54 PM, Marek Vasut wrote:
> 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.
I call dcache_off() and icache_off() after scrubbing, and I
verified the MMU control register indicated they were off.
>> 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.
Maybe there is something wrong with the reset hooks? I could try
and clear the on chip RAM after U-Boot relocates just to see what
happens.  Or there is probably an enable for the hooks I could try
and disable.
>> 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.
>>
After scrubbing I first call flush_dcache_all(), then I added calls to
invalidate_icache_all() and invalidate_dcache_all(), and finally I
call dcache_off() and icache_off().  I wasn't sure about the order
I should call them, but there was no change.