From: Kirill Kapranov <kirill.kapranov@compulab.co.il>
To: a.zummo@towertech.it, alexandre.belloni@bootlin.com,
phdm@macqel.be, linux-rtc@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: Kirill Kapranov <kirill.kapranov@compulab.co.il>
Subject: [PATCH 3/4] dt-bindings: rtc: abracon,abx80x: Add xt-frequency property
Date: Mon, 29 Mar 2021 00:02:31 +0300 [thread overview]
Message-ID: <20210328210232.10395-4-kirill.kapranov@compulab.co.il> (raw)
In-Reply-To: <20210328210232.10395-1-kirill.kapranov@compulab.co.il>
Add the string property "xt-frequency" to control xtal calibration of the
RTC. This allows to improve the RTC accuracy using a Distributed Digital
Calibration function. See: ch. 5.9.1 of
AB08XX Series Ultra Low Power RTC IC User's Guide
https://abracon.com/realtimeclock/AB08XX-Application-Manual.pdf
Signed-off-by: Kirill Kapranov <kirill.kapranov@compulab.co.il>
---
Documentation/devicetree/bindings/rtc/abracon,abx80x.txt | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt b/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt
index 4c545ece33b5..fac36db7460e 100644
--- a/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt
+++ b/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt
@@ -41,3 +41,16 @@ property to enable the output:
"1_min", "16384_Hz", "100_Hz", "1_hour", "1_day", "TIRQ", "nTIRQ",
"1_year", "1_Hz_to_Counters", "1/32_Hz_from_Acal", "1/8_Hz_from_Acal",
"none"
+
+The RTCs support XT calibration that allows to improve the RTC accuracy.
+To perform the calibration follow the instruction:
+
+ Write the nominal XT frequency (in milliHerz) 32768000 to
+ /sys/class/rtc/your_rtc/xt-frequency
+ to ensure the calibration is not occurring.
+ Select the XT oscillator by writing by writing xtal to
+ /sys/class/rtc/your_rtc/oscillator
+ Configure the square wave SQW output by writing
+ 32768_Hz to /sys/class/rtc/your_rtc/sqw
+ Measure the square wave frequency on the output pin in milliHerz.
+ Assign the measured value to the property xt-frequency.
--
2.11.0
next prev parent reply other threads:[~2021-03-28 21:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-28 21:02 [PATCH 0/4] rtc:abx80x: Enable distributed digital calibration Kirill Kapranov
2021-03-28 21:02 ` [PATCH 1/4] dt-bindings: rtc: abracon,abx80x: Add sqw property Kirill Kapranov
2021-03-28 21:02 ` [PATCH 2/4] rtc: abx80x: Enable SQW output Kirill Kapranov
2021-03-29 0:34 ` kernel test robot
2021-03-29 6:19 ` Dan Carpenter
2021-03-30 15:28 ` Kirill Kapranov
2021-03-28 21:02 ` Kirill Kapranov [this message]
2021-03-28 21:02 ` [PATCH 4/4] rtc:abx80x: Enable xt digital calibration Kirill Kapranov
2021-04-09 10:46 ` Pavel Machek
2021-04-09 16:56 ` Kirill Kapranov
2021-03-28 21:14 ` [PATCH 0/4] rtc:abx80x: Enable distributed " Alexandre Belloni
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