| Message ID | 20240126115509.1459425-1-naresh.solanki@9elements.com |
|---|---|
| State | Accepted |
| Commit | f1f99fcbf997b50a32844c31523ed41da0428f08 |
| Headers | show |
| Series | dt-bindings: iio: afe: voltage-divider: Add io-channel-cells | expand |
2024-01-26 at 23:14, Conor Dooley wrote: > On Fri, Jan 26, 2024 at 11:10:36PM +0530, Naresh Solanki wrote: > I did look at what you have there and I think your dts is wrong. > > The iio-hwmon binding says: > | description: > > | Bindings for hardware monitoring devices connected to ADC controllers > | supporting the Industrial I/O bindings. > | > | io-channels: > | minItems: 1 > | maxItems: 51 # Should be enough > | description: > > | List of phandles to ADC channels to read the monitoring values > > And then you have: > | iio-hwmon { > | compatible = "iio-hwmon"; > | // Voltage sensors top to down > | io-channels = <&p12v_vd 0>, <&p5v_aux_vd 0>, <&p5v_bmc_aux_vd 0>, <&p3v3_aux_vd 0>, > | <&p3v3_bmc_aux_vd 0>, <&p1v8_bmc_aux_vd 0>, <&adc1 4>, <&adc0 2>, <&adc1 0>, > | <&p2V5_aux_vd 0>, <&p3v3_rtc_vd 0>; > | }; > | > | p12v_vd: voltage_divider1 { > | compatible = "voltage-divider"; > | io-channels = <&adc1 3>; > | #io-channel-cells = <1>; > | > | /* Scale the system voltage by 1127/127 to fit the ADC range. > | * Use small nominator to prevent integer overflow. > | */ > | output-ohms = <15>; > | full-ohms = <133>; > | }; > > A voltage divider is _not_ an ADC channel, so I don't know why you are > treating it as one in the iio-hwmon entry. Can you explain this please? This is the exact intent of the voltage divider (and the other bindings handled by the iio-rescaler). The raw ADC reports the voltage at its input, which is fine, but if there is an analog frontend in front of the ADC such as a voltage divider the voltage at the ADC is not the interesting property. You are likely to want the "real" voltage before the voltage divider to better understand the value. In this case it's much more interesting to see values such as 12.050V which is presumably close to the nominal voltage (12V? guessing from the node name) rather than some unscaled raw ADC voltage (in this example it would be ~1.359V, which tells you rather little w/o rescaling it first). It's all in the description of the binding... Cheers, Peter
diff --git a/Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml b/Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml index dddf97b50549..b4b5489ad98e 100644 --- a/Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml +++ b/Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml @@ -39,6 +39,9 @@ properties: description: | Channel node of a voltage io-channel. + '#io-channel-cells': + const: 1 + output-ohms: description: Resistance Rout over which the output voltage is measured. See full-ohms.
Add #io-channel-cells expected by driver. i.e., below is the message seen in kernel log: OF: /iio-hwmon: could not get #io-channel-cells for /voltage_divider1 TEST=Run below command & make sure there is no error: make DT_CHECKER_FLAGS=-m dt_binding_check -j1 Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com> --- Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml | 3 +++ 1 file changed, 3 insertions(+) base-commit: ecb1b8288dc7ccbdcb3b9df005fa1c0e0c0388a7