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

[Jason Rush <jarush@gmail.com>]

On 7/11/2018 8:48 AM, Marek Vasut wrote:
> On 07/11/2018 03:49 PM, Jason Rush wrote:
>> On 7/11/2018 3:55 AM, Marek Vasut wrote:
>>> On 07/11/2018 05:11 AM, Jason Rush wrote:
>>> [...]
>>>
>>>>>>>> However, if I press the HPS_RST push button on the SoCKit (which is connected
>>>>>>>> to power on reset), occasionally U-Boot will lock up while booting.  It always
>>>>>>>> boots and operates correctly from the initial power on, but it almost always
>>>>>>>> fails to boot after pressing the HPS_RST button.
>>>>>>>>
>>>>>>>> Usually after pressing the HPS_RST button, U-Boot makes it past the SPL, and
>>>>>>>> hangs somewhere after the call to setup_reloc() in ./common/board_f.c.  Once
>>>>>>>> it hangs there, pressing the HPS_RST button again usually causes the SPL to
>>>>>>>> hang while setting up the MMU (before my call to memset).  Eventually the
>>>>>>>> WDT kicks in, and it just keeps hanging up in the same place.  Once it gets in
>>>>>>>> this mode, the only way to recover it is by toggling power on the board.
>>>>>>>>
>>>>>>>> I spent a bunch of time today trying to track down where it was hanging, but
>>>>>>>> I couldn't pin point anything.  The MMU tables looked correct.  The MMU
>>>>>>>> registers looked good.  I'm not sure the best way to debug what's going on.
>>>>>>> Try triggering warm reset and cold reset via the reset register:
>>>>>>>
>>>>>>> mw 0xffd05004 1
>>>>>>> mw 0xffd05004 2
>>>>>>>
>>>>>>> Does it hang in one case and not in the other ?
>>>>>>>
>>>>>> It hangs in both cases.
>>>>>>
>>>>>> I did find that if I do not metset the last 1MiB of DRAM with the cache on,
>>>>>> both warm and cold resets work.
>>>>>>
>>>>>> I changed the ecc scrubbing to zero out the first 0x8000 bytes and the last
>>>>>> 0x10000 bytes before the MMU is setup and I enable dcache.  Then with
>>>>>> the dcache enabled, I zero out the rest of memory.  The resets work in this
>>>>>> case as well.  So there seems to be some side effect of clearing out the
>>>>>> relocate address space with the cache on.
>>>>> Can you investigate ?
>>>>>
>>>> I'd be happy to investigate more, but I'm not really sure what
>>>> my next step should be.
>>>>
>>>> Something appears to be happening differently when U-Boot
>>>> relocates if the dcache is on.  But don't know how to track it
>>>> down.
>>> IIRC I disabled cache after scrubbing.
>> 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.