phosphor-hwmon + phosphor-fan: Fan functional properties are mismatched when unplug fan

[Matthew Barth]

On 12/16/20 2:03 AM, Thu Nguyen wrote:
> Hi,
>
>
> In the current code of phosphor-hwmon, when flag 
> --enable-update-functional-on-fail is set. The fan functional DBus 
> property in sensors interface will be set to false when unplug fans 
> (FAN4_2).
>
> ~# busctl get-property xyz.openbmc_project.Hwmon-1644477290.Hwmon1 
> /xyz/openbmc_project/sensors/fan_tach/FAN4_2 
> xyz.openbmc_project.State.Decorator.OperationalStatus Functional
> b false
>
> AND the fan Value properties will keep the latest reading value before 
> unplug.
>
> ~# busctl get-property xyz.openbmc_project.Hwmon-1644477290.Hwmon1 
> /xyz/openbmc_project/sensors/fan_tach/FAN4_2 
> xyz.openbmc_project.Sensor.Value Value
>
> d 4794
>
> ~# busctl get-property xyz.openbmc_project.Hwmon-1644477290.Hwmon1 
> /xyz/openbmc_project/sensors/fan_tach/FAN4_2 
> xyz.openbmc_project.Sensor.Value Value
> d 4794
>
> This cause phosphor-fan-monitor failed to detect the fan failure so 
> the fan functional are wrong.
>
> busctl get-property xyz.openbmc_project.Inventory.Manager 
> /xyz/openbmc_project/inventory/system/chassis/motherboard/FAN4_2 
> xyz.openbmc_project.State.Decorator.OperationalStatus Functional
> b true
>
> Should phosphor-hwmon keep updating the fan value Dbus properties with 
> error code when the fans is nonfunctional? Or phosphor-fan-monitor 
> should also check the fan functional in sensor interface to update fan 
> functional in inventory interface?
>
I recall this was something that would be needed in phosphor-fan-monitor 
when a fan's sensor is marked faulted since the value should no longer 
be trusted by phosphor-fan-monitor. A phosphor-fan-monitor configuration 
option needs to be added per fan sensor to check the sensor's functional 
property and use that to update the fan's functional state in inventory 
as well.

Please feel free to submit a patch to add this configuration option to 
drive setting the fan's functional state in inventory based on the state 
of a fan sensor's functional state.


Matt

>
> Regards.
>
> Thu Nguyen.
>
>
>