Re: [PATCH V5 3/4] hwmon: ina3221: Add support for channel summation disable

[Jon Hunter <jonathanh@nvidia.com>]

Hi Jean, Guenter,

On 29/09/2023 11:36, Jon Hunter wrote:
> From: Ninad Malwade <nmalwade@nvidia.com>
> 
> The INA3221 allows the Critical alert pin to be controlled by the
> summation control function. This function adds the single
> shunt-voltage conversions for the desired channels in order to compare
> the combined sum to the programmed limit. The Shunt-Voltage Sum Limit
> register contains the programmed value that is compared to the value in
> the Shunt-Voltage Sum register in order to determine if the total summed
> limit is exceeded. If the shunt-voltage sum limit value is exceeded, the
> Critical alert pin pulls low.
> 
> For the summation limit to have a meaningful value, we have to use the
> same shunt-resistor value on all included channels. Unless equal
> shunt-resistor values are used for each channel, the summation control
> function cannot be used and it is not enabled by the driver.
> 
> To address this, add support to disable the summation of specific
> channels via device tree property "ti,summation-disable". The channel
> which has this property would be excluded from the calculation of
> summation control function.
> 
> For example, summation control function calculates Shunt-Voltage Sum as:
> 
> - input_shunt_voltage_summation = input_shunt_voltage_channel1
>                                  + input_shunt_voltage_channel2
>                                  + input_shunt_voltage_channel3
> 
> If we want the summation to only use channel1 and channel3, we can add
> 'ti,summation-disable' property in device tree node for channel2. Then
> the calculation will skip channel2.
> 
> - input_shunt_voltage_summation = input_shunt_voltage_channel1
>                                  + input_shunt_voltage_channel3
> 
> Note that we only want the channel to be skipped for summation control
> function rather than completely disabled. Therefore, even if we add the
> property 'ti,summation-disable', the channel is still enabled and
> functional.
> 
> Finally, create debugfs entries that display if summation is disabled
> for each of the channels.
> 
> Signed-off-by: Rajkumar Kasirajan <rkasirajan@nvidia.com>
> Signed-off-by: Ninad Malwade <nmalwade@nvidia.com>
> Co-developed-by: Jon Hunter <jonathanh@nvidia.com>
> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>


Any feedback on this?

Thanks
Jon

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