Re: [PATCH] i2c: designware: use enable on resume instead initialization

christian.ruppert
2015-06-24T14:04:59Z

Dear Lucas,

"De Marchi, Lucas" <lucas.demarchi@intel.com> wrote on 24.06.2015
14:56:19:
> On Wed, 2015-06-24 at 14:27 +0300, Mika Westerberg wrote:
> > On Wed, Jun 24, 2015 at 09:36:43AM +0200,
christian.ruppert@alitech.com wrot
> > e:
> > > Dear Lucas,
> > >
> > > Lucas De Marchi <lucas.de.marchi@gmail.com> wrote on 23.06.2015
19:02:03:
> > > > On Tue, Jun 23, 2015 at 1:45 PM, <christian.ruppert@alitech.com>
wrote:
> > > > > Hello,
> > > > >
> > > > > Christian Ruppert/ALi_GVA/ALi wrote on 10.06.2015 17:05:16:
> > > > [...]
> > > > > The result is not very encouraging: Out of five (identical)
> designware
> > > > >
> > > i2c
> > > > > controllers we have on my test SOC, the first one
> initialises properly
> > > > >
> > > but
> > > > > the second one gets stuck in the famous irq loop right away when
the
> > > > > module is enabled in i2c_dw_init. The system never gets around
to try
> > > >
> > > > Are you using the pci or platform driver? I noticed yesterday the
pci
> > > > version is failing here with a NULL pointer dereference.
> > >
> > > The test was performed with the platform driver (instantiated
through
> > > device tree).
> > > I just re-checked and the ultimate problem which hangs/kills
thesystem in
> > >
> > > my case is the IRQ loop.
> > > I haven't observed any NULL pointer dereferences on the road.
> >
> > Thanks Christian for testing.
> >
> > Since the patch causes problems on your hardware, I don't think it is
> > good idea to merge it.
>
>
> Yeah, but it would be bad to ignore the problem as well. The way it is
now
> kills any possibility of using DW controller for reading sensors like
> gyroscope, accelerometer, barometer that have higher sampling rate etc.
I'll
> try to come up with a new patch but since I can't reproduce the problem
here
> it'd be good to know if there's any means for me to test.

I'll analyse the problem a bit further and send you a description (sda and
scl state at enable time) as soon as I can put my hands on an oscilloscope
one evening.

Greetings,
Christian