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Message-Id: <20181118042540.12697-5-matheus.bernardino@usp.br>
Date: Sun, 18 Nov 2018 02:25:37 -0200
From: Matheus Tavares <matheus.bernardino@....br>
To: Lars-Peter Clausen <lars@...afoo.de>,
Michael Hennerich <Michael.Hennerich@...log.com>,
Jonathan Cameron <jic23@...nel.org>,
Hartmut Knaack <knaack.h@....de>,
Peter Meerwald-Stadler <pmeerw@...erw.net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>
Cc: linux-iio@...r.kernel.org, devel@...verdev.osuosl.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
Alexandru Ardelean <alexandru.ardelean@...log.com>,
kernel-usp@...glegroups.com, victorcolombo@...il.com
Subject: [PATCH v2 4/7] dt-bindings:iio:resolver: Add docs for ad2s90
This patch adds the device tree binding documentation for the ad2s90
resolver-to-digital converter.
Signed-off-by: Matheus Tavares <matheus.bernardino@....br>
---
Changes in v2:
- Rewritten 'spi-cpol and spi-cpha' item to say that the device can
work in either mode (0,0) or (1,1) and explain how they should be
specified in DT.
.../bindings/iio/resolver/ad2s90.txt | 28 +++++++++++++++++++
1 file changed, 28 insertions(+)
create mode 100644 Documentation/devicetree/bindings/iio/resolver/ad2s90.txt
diff --git a/Documentation/devicetree/bindings/iio/resolver/ad2s90.txt b/Documentation/devicetree/bindings/iio/resolver/ad2s90.txt
new file mode 100644
index 000000000000..594417539938
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/resolver/ad2s90.txt
@@ -0,0 +1,28 @@
+Analog Devices AD2S90 Resolver-to-Digital Converter
+
+https://www.analog.com/en/products/ad2s90.html
+
+Required properties:
+ - compatible: should be "adi,ad2s90"
+ - reg: SPI chip select number for the device
+ - spi-max-frequency: set maximum clock frequency, must be 830000
+ - spi-cpol and spi-cpha:
+ Either SPI mode (0,0) or (1,1) must be used, so specify none or both of
+ spi-cpha, spi-cpol.
+
+Note about max frequency:
+ Chip's max frequency, as specified in its datasheet, is 2Mhz. But a 600ns
+ delay is expected between the application of a logic LO to CS and the
+ application of SCLK, as also specified. And since the delay is not
+ implemented in the spi code, to satisfy it, SCLK's period should be at most
+ 2 * 600ns, so the max frequency should be 1 / (2 * 6e-7), which gives
+ roughly 830000Hz.
+
+Example:
+resolver@0 {
+ compatible = "adi,ad2s90";
+ reg = <0>;
+ spi-max-frequency = <830000>;
+ spi-cpol;
+ spi-cpha;
+};
--
2.18.0
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