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

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Date:   Thu, 7 Sep 2017 17:27:25 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Andrew Jeffery <andrew@...id.au>
Cc:     linux-hwmon@...r.kernel.org, jdelvare@...e.com, corbet@....net,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        openbmc@...ts.ozlabs.org, joel@....id.au
Subject: Re: [PATCH] hwmon: pmbus: Make reg check and clear faults functions
 return errors

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. 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 ? Does the driver fail to instantiate ?

Guenter