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

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

On Tue, Jun 11, 2013 at 08:40:37PM +0200, Wolfram Sang wrote:
> On Fri, Jun 07, 2013 at 03:01:34PM +0200, Christian Ruppert wrote:
> > Hi Andy,
> > 
> > I like your patch and I just did some testing on it. Unluckily, it
> > doesn't solve the lock-up problem.
> > 
> > I haven't investigated any further but I suspect that on top of the
> > cases I observed when debugging this (interrupts after initialisation of
> > dev, easy to prove) there are more obscure cases in which interrupts are
> > generated in an unexpected manner after errors. The interrupt-driven
> > transfer state machine of the driver implicitly relies on the fact that
> > all updates of dev which are related to the same transfer are performed
> > between the mutex_lock and mutex_unlock calls in i2c_dw_xfer. Thus, I
> > decided it was safer to disable the block before releasing the mutex
> > when I wrote my patch.
> > 
> > That said, I think the sequencing at transfer initialisation is more
> > logical with your patch and I wonder if it is still worth applying. Any
> > other opinions on this?
> 
> Ping. There are:
> 
> [V2] i2c: designware: fix race between subsequent xfers
> [RFC] i2c-designware-core: disable adapter before fill dev structure
> 
> What is the consensus of those two patches?

Although I almost like Andy's code better than my own it doesn't seem to
fix the issue we're aiming at (system lock ups due to undesired
interrupts) in all cases. The "[V2] i2c: designware: fix race between
subsequent xfers" is currently the only patch preventing those lock ups
in our tests.

That said, IMHO Andy's patch seems to be a valuable code clean up
nevertheless and could be applied in addition to the other. I suggest I
give the combination of both patches some additional testing on the
occasion and tag Andy's RFC with tested-by me in case it's stable.

Greetings,
  Christian

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