linux-kernel - [PATCH v2 1/3] dt-bindings: iio: adc: stm32: add support for diff channels

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Date:   Wed, 25 Oct 2017 11:27:43 +0200
From:   Fabrice Gasnier <fabrice.gasnier@...com>
To:     <jic23@...nel.org>, <robh+dt@...nel.org>
CC:     <linux@...linux.org.uk>, <mark.rutland@....com>,
        <mcoquelin.stm32@...il.com>, <alexandre.torgue@...com>,
        <lars@...afoo.de>, <knaack.h@....de>, <pmeerw@...erw.net>,
        <fabrice.gasnier@...com>, <linux-iio@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <benjamin.gaignard@...aro.org>,
        <benjamin.gaignard@...com>
Subject: [PATCH v2 1/3] dt-bindings: iio: adc: stm32: add support for diff channels

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 <fabrice.gasnier@...com>
---
Changes in v2:
- Add differential channels example
- Add a note on mixed single-ended / differential channels
---
 .../devicetree/bindings/iio/adc/st,stm32-adc.txt   | 24 ++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
index 48bfcaa3..e8bb824 100644
--- a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
+++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
@@ -62,6 +62,15 @@ 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
   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.
+  Depending on part used, some channels can be configured as differential
+  instead of single-ended (e.g. stm32h7). List here positive and negative
+  inputs pairs as <vinp vinn>, <vinp vinn>,... vinp and vinn are numbered
+  from 0 to 19 on stm32h7)
+  Note: At least one of "st,adc-channels" or "st,adc-diff-channels" is required.
+  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).
 - #io-channel-cells = <1>: See the IIO bindings section "IIO consumers" in
   Documentation/devicetree/bindings/iio/iio-bindings.txt
 
@@ -111,3 +120,18 @@ Example:
 		...
 		other adc child nodes follow...
 	};
+
+Example to setup:
+- channel 1 as single-ended
+- channels 2 & 3 as differential (with resp. 6 & 7 negative inputs)
+
+	adc: adc@...22000 {
+		compatible = "st,stm32h7-adc-core";
+		...
+		adc1: adc@0 {
+			compatible = "st,stm32h7-adc";
+			...
+			st,adc-channels = <1>;
+			st,adc-diff-channels = <2 6>, <3 7>;
+		};
+	};
-- 
1.9.1