snps,dwmac interrupt storm (Was: ARC770: "unexpected IRQ trap at vector 00" during boot)

[Alex]

On 07/25/2017 08:08 PM, Vineet Gupta wrote:

Hi Vineet,

> On 07/26/2017 01:41 AM, Alexey Brodkin wrote:
>> BTW what is your exact kernel version?
>>
>> In the meantime we'll try to revisit rework of ARC's INTC init
>> procedure  but
>> I cannot promise anything very soon as I'm on ETO this week but we'll
>> see how it goes.
>
> And exactly do we intend to rework - AFAIK nothings really broken at the
> moment in ARC intc handling !

I have tried the workarouns I mentioned on top of linux 4.9.34, and it 
works exactly as expected. however, on top of 4.13-rc3 [1], the story is 
a lot different. As soon as I release the GMAC from reset, the boot 
stops. I can single-step through JTAG, and see that the GMAC sends an 
interrupt storm. The kernel doesn't have time to move on with the dwmac 
initialization and register the interrupt, and that's that.

I'd file this under both 'regression' and 'bug' categories.

Not sure what changed under the hood from 4.9 to 4.13-rc3 to cause such 
a drastically different behavior. I can't really do much else as 
workarounds, since the GMAC registers are not writable while the GMAC is 
in reset.

Alex

[1] https://github.com/mrnuke-adaptrum/linux/commits/patch-v2-anarion-wip


> -Vineet