Re: [PATCH v2 3/3] hwmon: ltc2990: support all measurement modes

[Tom Levens]

On Thu, 29 Jun 2017, Mike Looijmans wrote:

> On 28-06-17 19:02, Tom Levens wrote:
> >  On Wed, 28 Jun 2017, Guenter Roeck wrote:
> >
> > >  On Wed, Jun 28, 2017 at 05:29:38PM +0200, Tom Levens wrote:
> > > > 
> > >  [ ... ]
> > > 
> > > > > 
> > > > > >  Whatever happened to this patch though? It didn't make it to 
> > > > > >  mainline,
> > > > > >  otherwise I'd have found it sooner...
> > > > > > 
> > > > >  I'll have to look it up, but I guess I didn't get an updated 
> > > > >  version.
> > > > 
> > > >  As far as I remember I had a working V3 of this patch, but it is 
> > > >  entirely
> > > >  possible that it was never submitted as I have been busy with other 
> > > >  projects
> > > >  recently. I'll dig it out and check that it is complete.
> > > > 
> > >  FWIW, I don't see it at
> > >  https://patchwork.kernel.org/project/linux-hwmon/list/?submitter=171225&state=*
> > > 
> > >  Maybe you were waiting for a reply from Rob. Either case, it might make
> > >  sense to only provide valid modes, ie to abstract the mode bits from the
> > >  hardware, such as
> > > 
> > >  0 - internal temp only
> > >  1 - Tr1
> > >  2 - V1
> > >  3 - V1-V2
> > >  4 - Tr2
> > >  5 - V3
> > >  6 - V3-V4
> > >  7 to 14 - per bit 0..2
> > > 
> > >  Guenter
> > >
> >
> >  You are right, there was still an open question about how best to handle
> >  the mode selection in DT.
> >
> >  In the latest version of my patch I have it implemented as an array for
> >  setting the two values, for example:
> >
> >       lltc,meas-mode = <7 3>;
> >
> >  This sets bits [2..0] = 7 and [4..3] = 3. Of course these could be split
> >  into two DT properties, but I was unsure what to name them as both fields
> >  are called "mode" in the datasheet and "mode-43"/"mode-20" (or similar) is
> >  ugly.
> >
> >  With regards to your proposal, it is not clear to me whether the modes
> >  which have the same result are exactly equivalent. Does disabling a
> >  measurement with the mode[4..3] bits really leaves the part in a safe
> >  state for all possible HW connections? With this doubt in my head, I would
> >  prefer to keep the option available to the user to select any specific
> >  mode. But I am open to suggestions.
> >
> >  Mike, if you would like to test it, the latest version of my code is here:
> >
> >  https://github.com/levens/ltc2990/blob/dev/drivers/hwmon/ltc2990.c
>
> I pulled your patches, added two lines to the devicetree and it works fine, 
> I'm seeing plausible results:
> root@topic-miami:/sys/class/hwmon# grep . */*
> hwmon0/name:battery-gauge
> hwmon0/temp1_input:291700
> hwmon1/in0_input:3258
> hwmon1/in1_input:1824
> hwmon1/in2_input:1916
> hwmon1/in3_input:1512
> hwmon1/in4_input:2066
> hwmon1/name:ltc2990
> hwmon1/temp1_input:28062
> hwmon1/uevent:OF_NAME=ltc2990
> hwmon1/uevent:OF_FULLNAME=/gpios-i2c@50/ltc2990@4c
> hwmon1/uevent:OF_COMPATIBLE_0=lltc,ltc2990
> hwmon1/uevent:OF_COMPATIBLE_N=1
> hwmon2/curr1_input:1825
> hwmon2/curr2_input:349
> hwmon2/in0_input:3244
> hwmon2/name:ltc2990
> hwmon2/temp1_input:31500
> hwmon2/uevent:OF_NAME=ltc2990
> hwmon2/uevent:OF_FULLNAME=/gpios-i2c@52/ltc2990@4C
> hwmon2/uevent:OF_COMPATIBLE_0=ltc2990
> hwmon2/uevent:OF_COMPATIBLE_N=1
>
>
> As you can see, two ltc2990 on two busses, one measuring current and one 
> measuring 4 independent voltages.
>
> I also like your implementation of the mode setting better, it's much simpler 
> than mine. And you've solved a bug in the temperature reading as well.

Excellent, I am glad it also works for you! In this case, I would propose 
that I submit the V3 of the patch for further discussion.

Thanks,

> Kind regards,
>
> Mike Looijmans
> System Expert
>
> TOPIC Products
> Materiaalweg 4, NL-5681 RJ Best
> Postbus 440, NL-5680 AK Best
> Telefoon: +31 (0) 499 33 69 79
> E-mail: mike.looijmans@xxxxxxxxxxxxxxxxx
> Website: www.topicproducts.com
>
> Please consider the environment before printing this e-mail