On Fri, Sep 29, 2023 at 11:36:49AM +0100, Jon Hunter wrote: > From: Ninad Malwade <nmalwade@xxxxxxxxxx> > > 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@xxxxxxxxxx> > Signed-off-by: Ninad Malwade <nmalwade@xxxxxxxxxx> > Co-developed-by: Jon Hunter <jonathanh@xxxxxxxxxx> > Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx> Applied. Thanks, Guenter
