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@xxxxxxxxxxxxxx> --- 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
