Configuring shunt_resistor in hwmon

[James Feist]

On 1/6/20 1:29 PM, Alex Qiu wrote:
> Hi James,
> 
> Thanks for your quick reply and reviewing my code in the morning!
> 
> That looks interesting, so this ScaleFactor will be used to multiply the 
> voltage value from hwmon without setting the shunt_resistor explicitly? 
> I do have a little concern on the resolution, because it's only 
> reporting 0.165V with default shunt_resistor setting, but we'll try and 
> see if this will work for our case. In the meantime, do you know any 
> other method that will work?

That's all I'm aware of in dbus-sensors. We have a voltage divider 
in-front of our ADC channels, so we use this scale factor to calculate 
the actual voltage. Anything else I think you'd need to add as a new 
change if you're using dbus-sensors. I'm not sure if phosphor-hwmon 
offers anything you could use or not.

> 
> Thank you!
> 
> - Alex Qiu
> 
> 
> On Mon, Jan 6, 2020 at 1:21 PM James Feist <james.feist at linux.intel.com 
> <mailto:james.feist at linux.intel.com>> wrote:
> 
>     On 1/6/20 1:16 PM, Alex Qiu wrote:
>      > Hi OpenBMC folks,
>      >
>      > Is there a way to configure the shunt_resistor value for a hwmon
>     with
>      > entity-manager or other modules?
> 
>     Have you seen this?
>     https://github.com/openbmc/entity-manager/blob/0cbe6bf34101bab7544b40011868efc5145c0804/configurations/WFT%20Baseboard.json#L7
> 
>     For Entity-Manager + dbus-sensors.
> 
>      > We need to configure this value to make
>      > the INA230 report correct voltage, but for now I don't find
>     anything in
>      > the code for it. Shall this be a feature to implement? Thanks!
>      >
>      > - Alex Qiu
>