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

[Alexey Brodkin]

Hi Alex,

On Wed, 2017-08-02 at 11:53 +0530, Vineet Gupta wrote:
> On 08/02/2017 03:03 AM, Alex wrote:
> > 
> > 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.

The only guess I have given mentioned symptoms is you're somehow affected by
90f522a20e3d "NET: dwmac: Make dwmac reset unconditional", see:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=90f522a20e3d16d153e5a5f84cf4ff92281ee417

I guess what happens in 4.13-rc3 with that patch in place your previous work-around
gets reset together with GMAC on driver probe.

So just try to revert that patch for a moment and let me know if that was the case.

-Alexey