[RESEND,PATCHv6 1/1] Add support for GMT G762/G763 PWM fan controllers

[Guenter Roeck]

On Wed, Jun 19, 2013 at 11:26:33PM +0200, Simon Guinot wrote:
> On Wed, Jun 19, 2013 at 01:53:21PM -0700, Guenter Roeck wrote:
> > On Wed, Jun 19, 2013 at 10:15:56PM +0200, Arnaud Ebalard wrote:
> > > Hi Simon,
> > > 
> > > Simon Guinot <simon.guinot at 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 ?
> 
> The controller is the very same as for the ReadyNAS Duo v2. It is built
> in the Marvell Kirkwood SoC and the driver is i2c-mv64xxx.
> 
> I will try an another board to see if I reproduce the error.
> 
Might be a flaky i2c connection or a problematic board. The i2c-mv64xxx driver
does return ENODEV in error cases. I submitted a patch to change it to ENXIO;
we'll see if it gets accepted.

Guenter

> Regards,
> 
> Simon
> 
> > 
> > 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+ 
> > >