linux-kernel - [PATCH v2 2/3] dt-bindings: iio: adc: stm32: add optional st,min-sample-time-nsecs

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Date:   Mon, 24 Jul 2017 18:10:39 +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>
Subject: [PATCH v2 2/3] dt-bindings: iio: adc: stm32: add optional st,min-sample-time-nsecs

STM32 ADC allows each channel to be sampled with a different sampling
time. There's an application note that deals with this: 'How to get
the best ADC accuracy in STM32...' It basically depends on analog input
signal electrical properties (depends on board).

Add optional 'st,min-sample-time-nsecs' property so this can be tuned
in dt.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
---
Changes in v2:
- Use 'st,min-sample-time-nsecs' instead of 'min-sample-time'.
---
 Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
index 8310073..48bfcaa3 100644
--- a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
+++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
@@ -74,6 +74,11 @@ Optional properties:
   * can be 6, 8, 10 or 12 on stm32f4
   * can be 8, 10, 12, 14 or 16 on stm32h7
   Default is maximum resolution if unset.
+- st,min-sample-time-nsecs: Minimum sampling time in nanoseconds.
+  Depending on hardware (board) e.g. high/low analog input source impedance,
+  fine tune of ADC sampling time may be recommended.
+  This can be either one value or an array that matches 'st,adc-channels' list,
+  to set sample time resp. for all channels, or independently for each channel.
 
 Example:
 	adc: adc@...12000 {
-- 
1.9.1