From mboxrd@z Thu Jan  1 00:00:00 1970
From: Guenter Roeck <linux@roeck-us.net>
Subject: Re: [RESEND,PATCHv6 1/1] Add support for GMT G762/G763 PWM fan
 controllers
Date: Wed, 19 Jun 2013 13:53:21 -0700
Message-ID: <20130619205321.GA7625@roeck-us.net>
References: <87sj0jhuhn.fsf@natisbad.org>
 <20130617101948.GY7626@kw.sim.vm.gnt>
 <8761x9svpf.fsf@natisbad.org>
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To: Arnaud Ebalard <arno@natisbad.org>
Cc: Simon Guinot <simon.guinot@sequanux.org>, Andrew Lunn <andrew@lunn.ch>, Russell King - ARM Linux <linux@arm.linux.org.uk>, Jason Cooper <jason@lakedaemon.net>, linux-doc@vger.kernel.org, devicetree-discuss@lists.ozlabs.org, Olivier Mouchet <olivier.mouchet@gmail.com>, Rob Herring <rob.herring@calxeda.com>, lm-sensors@lm-sensors.org, Grant Likely <grant.likely@secretlab.ca>, Rob Landley <rob@landley.net>, Jean Delvare <khali@linux-fr.org>, Linux ARM Kernel Mailing List <linux-arm-kernel@lists.infradead.org>
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On Wed, Jun 19, 2013 at 10:15:56PM +0200, Arnaud Ebalard wrote:
> Hi Simon,
> 
> Simon Guinot <simon.guinot@sequanux.org> writes:
> 
> > I have tested this patch on my 2Big Network v2 board.
> >
> > Sometimes I get a weird "No such device" error while reading or writing
> > the hwmon sysfs attributes. For example:
> >
> > # cat pwm1
> > cat: read error: No such device
> > # cat pwm1
> > 0
> 
This is odd, since ENODEV should not be returned as error code from i2c read
operations.

What is the i2c controller ?

Thanks,
Guenter

> Weird, I cannot reproduce that at all on my ReadyNAS Duo v2.
> 
> > Note, that if the same command is executed again (just after the faulty
> > one), then it will succeed most of the time. The errors seems to happen
> > quite randomly and not very often. I'd say one time over ten tries.
> > I suppose this error is now visible due to the enhanced error path in
> > g762_update_client. It looks like we learn something by checking the
> > return value for i2c_smbus_read_byte_data :)
> >
> > Except that, all is working as expected. This new version fixes
> > effectively open-loop driving when the set_cnt register is set to 0xff.
> >
> > Also I am planning (hopefully this Wednesday) to test your patch on my
> > 5Big Network v2 board. This last also embed a g762 controller but with a
> > three wires fan instead. Then, I should be able to test the closed-loop
> > mode behaviour.
> 
> Thanks for your tests, Simon.
> 
> Cheers,
> 
> a+ 
>