Re: [RFC PATCH] i2c-designware-core: disable adapter before fill dev structure

[Christian Ruppert <christian.ruppert-ux6zf3SgZrrQT0dZR+AlfA@public.gmane.org>]

On Thu, Jun 13, 2013 at 11:33:56AM +0300, Andy Shevchenko wrote:
> On Thu, 2013-06-13 at 10:16 +0200, Christian Ruppert wrote: 
> > As promised, I gave this one some over-night stress testing and I can
> > confirm what I said previously:
> > 
> > - The patch does _not_ solve the interrupt loop lockups on its own.
> 
> So, it just means my assumptions about what is happening there were
> wrong.

So were my initial ones... Or at least insufficient.

> > - The patch works well in conjunction with
> >   http://patchwork.ozlabs.org/patch/249622/ (which in turn depends on
> >   Mika's patch). Under this condition you can assume
> >   Tested-By: Christian Ruppert <christian.ruppert-ux6zf3SgZrrQT0dZR+AlfA@public.gmane.org>
> > 
> > I still think the code is more logical with this patch than without it
> > and I am in favour of applying both (if Andy agrees that is).
> 
> Since my patch doesn't fix anything, I think we may drop it away.
> 
> >  We must keep in mind, however, that http://patchwork.ozlabs.org/patch/249622
> > does fix a real problem we can observe on our chip and for our TB10x
> > product we do require some form of it for stability reasons.
> 
> I feel like a real fix is to add a memory barier to make changes in the
> structure consistent. However, I have no clue where.

I'm still not sure about the interrupt behaviour of the dw-i2c block in
the case of error (and since our problem is fixed it's difficult to
justify spending time to investigate further). I suspect that the thing
in some situations sends spurious interrupts which confuse the state
machine - in which case memory barriers won't help us either.

Greetings,
  Christian

-- 
  Christian Ruppert              ,          <christian.ruppert@abilis.com>
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