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    Subject[PATCH 3/4] dt-bindings: rtc: abracon,abx80x: Add xt-frequency property
    Date
    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
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