linux-kernel - [PATCH v2 2/5] dt-binding: pcf8523: add xtal load capacitance

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Message-Id: <20190108185414.26922-3-sam@ravnborg.org>
Date:   Tue,  8 Jan 2019 19:54:11 +0100
From:   Sam Ravnborg <sam@...nborg.org>
To:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Andrew Jeffery <andrew@...id.au>,
        Fabio Estevam <fabio.estevam@....com>,
        Joel Stanley <joel@....id.au>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Urs Fässler <urs.fassler@....ch>,
        Shawn Guo <shawnguo@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-rtc@...r.kernel.org
Cc:     Sam Ravnborg <sam@...nborg.org>,
        Søren Andersen <san@...v.dk>
Subject: [PATCH v2 2/5] dt-binding: pcf8523: add xtal load capacitance

The NXP pcf8523 supports two different xtal load capacitance
- 7000fF  (7pF)    HW default
- 12500fF (12.5pF) Minimum power consumption, driver default

To obtain a precise RTC the pcf8523 must be configured
with the correct capacitance load of the xtal.

Add a property to specify the xtal capacitance load.
The default value matches that of the current Linux driver.

With a dedicated binding remove the entry in rtc.txt

Signed-off-by: Søren Andersen <san@...v.dk>
Signed-off-by: Sam Ravnborg <sam@...nborg.org>
Cc: Alessandro Zummo <a.zummo@...ertech.it>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: Rob Herring <robh+dt@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
---
 Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt | 18 ++++++++++++++++++
 Documentation/devicetree/bindings/rtc/rtc.txt         |  1 -
 2 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt

diff --git a/Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt b/Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt
new file mode 100644
index 000000000000..214ac5d26df7
--- /dev/null
+++ b/Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt
@@ -0,0 +1,18 @@
+* NXP PCF8523 Real Time Clock
+
+Required properties:
+- compatible: Should contain "nxp,pcf8523".
+- reg: I2C address for chip.
+
+Optional property:
+- quartz-load-femtofarads: The capacitive load of the quartz(x-tal),
+  expressed in femto Farad (fF). Valid values are 7000 and 12500.
+  Default value (if no value is specified) is 12500fF.
+
+Example:
+
+pcf8523: pcf8523@68 {
+	compatible = "nxp,pcf8523";
+	reg = <0x68>;
+	quartz-load-femtofarads = <7000>;
+};
diff --git a/Documentation/devicetree/bindings/rtc/rtc.txt b/Documentation/devicetree/bindings/rtc/rtc.txt
index 7c8da6926095..e07b15d151ac 100644
--- a/Documentation/devicetree/bindings/rtc/rtc.txt
+++ b/Documentation/devicetree/bindings/rtc/rtc.txt
@@ -51,7 +51,6 @@ isil,isl12022		Intersil ISL12022 Real-time Clock
 microcrystal,rv3029	Real Time Clock Module with I2C-Bus
 nxp,pcf2127		Real-time clock
 nxp,pcf2129		Real-time clock
-nxp,pcf8523		Real-time Clock
 nxp,pcf8563		Real-time clock/calendar
 nxp,pcf85063		Tiny Real-Time Clock
 pericom,pt7c4338	Real-time Clock Module
-- 
2.12.0