Hi Jonathan,
On 1/1/2024 11:32 PM, Jonathan Cameron wrote:
On Sun, 31 Dec 2023 22:42:36 +0530
Jishnu Prakash <quic_jprakash@xxxxxxxxxxx> wrote:
For the PMIC5-Gen3 type PMICs, ADC peripheral is present in HW for the
+
+ label:
+ $ref: /schemas/types.yaml#/definitions/string
+ description: |
+ ADC input of the platform as seen in the schematics.
+ For thermistor inputs connected to generic AMUX or GPIO inputs
+ these can vary across platform for the same pins. Hence select
+ the platform schematics name for this channel.
defined in adc.yaml, so should just have a reference to that here.
+
+ qcom,decimation:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: |
+ This parameter is used to decrease ADC sampling rate.
+ Quicker measurements can be made by reducing decimation ratio.
Why is this in DT rather than as a userspace control?
We don't intend this property to be something that can be controlled
from userspace - if a client wants to read an ADC channel from
userspace, we only intend to provide them the processed value,
calculated with a fixed set of ADC properties mentioned in the
corresponding channel node in DT.
+ enum: [ 85, 340, 1360 ]
+ default: 1360
+
+
+ qcom,hw-settle-time:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: |
+ Time between AMUX getting configured and the ADC starting
+ conversion. The 'hw_settle_time' is an index used from valid values
+ and programmed in hardware to achieve the hardware settling delay.
+ enum: [ 15, 100, 200, 300, 400, 500, 600, 700, 1000, 2000, 4000,
+ 8000, 16000, 32000, 64000, 128000 ]
+ default: 15
only currently defined for muxes but we have settle-time-us which has benefit of
providing the units (which are missing here from the description as well)
+
+ qcom,avg-samples:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: |
+ Number of samples to be used for measurement.
+ Averaging provides the option to obtain a single measurement
+ from the ADC that is an average of multiple samples. The value
+ selected is 2^(value).
Why is this in dt? Why not just userspace control (in_voltageX_oversampling_ratio
If it needs to be, we do have standard DT bindings for it in adc.yaml
avg-samples is also something we don't want the client to modify from
userspace. As for using adc.yaml, I think I could use settling-time-us
and oversampling-ratio from it for the above two properties.
However, Krzysztof has mentioned in another comment that I should put
properties common to ADC5 Gen3 and older QCOM VADC devices in a common
schema. If I now try replacing the existing qcom,hw-settle-time and
qcom,avg-samples properties with settling-time-us and oversampling-ratio
for older devices too, I would have to make several DT changes for
existing devices...are you fine with this? Or should I just replace
these two properties for ADC5 Gen3?
I'll address your other comments in the next patchset.
Thanks,
Jishnu
