[PATCH V4 2/2] riscv: board: Support OpenPiton SoC

[Tianrui Wei]

Hi Sean,

On 5/13/2021 1:14 AM, Sean Anderson wrote:
>
> [snip]
>
>> On 5/8/2021 11:14 PM, Sean Anderson wrote:
>>> On 5/8/21 12:57 AM, Tianrui Wei wrote:
>>>> On 5/7/2021 9:03 PM, Sean Anderson wrote:
>>>>> On 5/6/21 11:48 PM, Tianrui Wei wrote:
>>>>>> On 5/7/2021 11:41 AM, Sean Anderson wrote:
>>>>>>> On 5/6/21 11:28 PM, Tianrui Wei wrote:
>>>>>>>> On 5/7/2021 11:15 AM, Sean Anderson wrote:
>>>>>>>>> On 5/6/21 11:06 PM, Tianrui Wei wrote:
>>>>>>>>>> On 5/7/2021 10:32 AM, Sean Anderson wrote:
>>>>>>>>>>> Please use a log without debug uart.
>>>>>>>>>>>
>>>>>>>>>> So this is the part where it was a little confusing. Disabling
>>>>>>>>>> debug uart acutally doesn't work for some reason, so we had to
>>>>>>>>>> keep it open. Will submit another patch if we got it working
>>>>>>>>>> with debug uart turned off.
>>>>>>>>>
>>>>>>>>> This is a bit of a strange request, but can you try adding 
>>>>>>>>> some nops()
>>>>>>>>> (around 10-30) to some function (e.g. board_init). I've been 
>>>>>>>>> having
>>>>>>>>> alignment problems in k210, so it could be something similar.
>>>>>>>>>
>> I was wondering if you have any idea what may cause the alignment
>> problems, we're also hitting it constantly and adding nops seems to
>> have no impact so far.
>
> I have no idea :)
>
> If adding nop()s doesn't solve it, it may not be an alignment problem.
> You can also try switching from -Os to -O2, which should move things
> around a bit.
>
> My attempts to dig into this have been stymied by the poor debugging
> tools for the k210. The upstream openocd port only supports debugging
> hart 0. While Canaan's fork supports debugging both harts, you must pick
> the one to debug when launching the debugger. And both debuggers are
> very buggy themselves.
>
> The other problem on the k210 at least is that the typical failure mode
> (trying to read from unaddressable/unmapped addresses) hangs the bus.
> This also has the tendancy of hanging the jtag debug port.


I did try to switch from -Os to -O2, and it didn't help either. I've 
also encountered

the same debugger situation unfortunately, so I have not much luck 
finding the

faulty instruction either.  Maybe we should bring this issue up with the 
others along

the compilation error?


Thanks,

Tianrui


>
> --Sean