Re: [PATCH] hwmon: pmbus: Make reg check and clear faults functions return errors

[Guenter Roeck]

On 09/07/2017 06:02 PM, Andrew Jeffery wrote:
> On Thu, 2017-09-07 at 17:27 -0700, Guenter Roeck wrote:
> > On 09/07/2017 08:22 AM, Andrew Jeffery wrote:
> > > On Thu, 2017-09-07 at 06:40 -0700, Guenter Roeck wrote:
> > > > On 09/06/2017 04:32 PM, Andrew Jeffery wrote:
> > > >
> > > > > >     
> > > > > > Guess I need to dig up my eval board and see if I can reproduce the problem.
> > > > > > Seems you are saying that the problem is always seen when issuing a sequence
> > > > > > of "clear faults" commands on multiple pages ?
> > > > >
> > > > > Yeah. We're also seeing bad behaviour under other command sequences as well,
> > > > > which lead to this hack of a work-around patch[1].
> > > > >
> > > > > I'd be very interested in the results of testing against the eval board. I
> > > > > don't have access to one and it seems Maxim have discontinued them.
> > > >
> > > > Do you have a somewhat reliable means to reproduce the problem ?
> > >
> > > It seems we hit a bunch of problems by just continually
> > > binding/unbinding the driver, if you don't apply that hacky oneshot
> > > retry patch. We can hit problems (in our design?) with something like:
> > >
> > > # cd /sys/bus/i2c/drivers/max31785; \
> > > 	echo $addr > unbind; \
> > > 	while echo $addr > bind; \
> > > 	do echo $addr > unbind; echo -n .; done;
> > >
> > > It should hit issues covered by this patch, as the register checks are
> > > used in the operations used by probe.
> >
> > Hmm ... I didn't use your driver but my prototype driver which also supports
> > temperature and voltage attributes, so if anything it should create more
> > stress on the chip.
>
> I did add the temp and voltage attributes...
>
> Any chance you can give mine a try? I don't know what I would have done
> to invoke this kind of behaviour, so it would be useful to know whether
> or not it happens with one driver but not the other.

Will do.

> >   No error so far, after running the script for a couple
> > of minutes. How long does it take for errors to appear, and how do I see
> > that there is an error ?
>
> I'm seeing failures after anything from a handful of bind/unbinds, to
> hundreds of bind/unbinds. It seems to vary.
>
> > Does the driver fail to instantiate ?
>
> Typically probe fails so the loop exits. It usually gets -EIO and the
> shell spits out "No such device".
>
> Thanks for testing, it's a useful data point for us hunting down the
> source of our problems.
I aborted the test after ~2,500 loops without error.

Guenter