[PATCH 1/3] dt-bindings: iio: adc: stm32: add support for diff channels

On 10/24/2017 08:42 PM, Jonathan Cameron wrote:

On 24 October 2017 17:41:38 BST, Rob Herring [off-list ref] wrote:

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On Tue, Oct 17, 2017 at 03:15:43PM +0200, Fabrice Gasnier wrote:

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STM32H7 ADC channels may be configured either as single-ended or
differential.
Add 'st,adc-diff-channels' property to support differential channels.
Differential channels are defined as a pair of positive and negative
inputs: vinp & vinn.

Signed-off-by: Fabrice Gasnier <redacted>
---
 Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt | 6

++++++

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 1 file changed, 6 insertions(+)

diff --git

a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt

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index 48bfcaa3..c3c8de1 100644

--- a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
+++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt

@@ -62,6 +62,12 @@ Required properties:
 - st,adc-channels: List of single-ended channels muxed for this ADC.
   It can have up to 16 channels on stm32f4 or 20 channels on

stm32h7, numbered

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   from 0 to 15 or 19 (resp. for in0..in15 or in0..in19).
+- st,adc-diff-channels: List of differential channels muxed for this

ADC.

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+  Depending on part used, some channels can be configured as

differential

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+  instead of single-ended (e.g. stm32h7). List here positive and

negative

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+  inputs pairs as <vinp vinn>, <vinp vinn>,... vinp and vinn are

numbered

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+  from 0 to 19 on stm32h7)
+  Note: At least one of "st,adc-channels" or "st,adc-diff-channels"

is required.

Wouldn't both present be invalid?

Hi Rob, Jonathan,

Probably invalid to have a number in both but some channels in each would be fine.

Yes, both properties can be used together. Some channels can be used as
single-ended and some other ones as differential (mixed). But channels
can't be configured both as single-ended and differential (invalid).

I'll mention this in the note, and also update differential channels
example:

Example to setup:
- channel 1 as single-ended
- channels 2 & 3 as differential (with resp. 6 & 7 negative inputs)

	adc: adc at 40022000 {
		compatible = "st,stm32h7-adc-core";
		...
		adc1: adc at 0 {
			compatible = "st,stm32h7-adc";
			...
			st,adc-channels = <1>;
			st,adc-diff-channels = <2 6>, <3 7>;
		};
	};

I will send V2 with these updates.

Thanks,
Best Regards,
Fabrice

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 - #io-channel-cells = <1>: See the IIO bindings section "IIO

consumers" in

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   Documentation/devicetree/bindings/iio/iio-bindings.txt
 
-- 
1.9.1