Zynqmp RTC

Introduction


The Zynq® UltraScale+™ MPSoC real time clock (RTC) provides the real time even when the device is powered off. When the device is off, the RTC is switched to the battery power supply. A battery-backed RAM (BBRAM) is provided for when device is operating in the battery mode. However, the RTC controller and user interface are only operational when the low-power domain supply is ON. The RTC has an alarm function that generates an alarm at a specific time and date with a 136-year range. The RTC also has periodic software calibration and logic to correct the static fractional inaccuracy of an oscillator.

HW/IP FEATURES:

Real-Time Clock (RTC) provides the following features:
  • Maintains the real time, even when the device is off (powered-off).
  • Has the capability to generate an alarm at a specific time and date.
  • Includes the means for periodic software calibration of the RTC.
  • Includes logic to correct the static fractional inaccuracy of the oscillator.
  • Keeps track of time within a window of more than 136 years (232 seconds) from a reference point.
  • Implemented as three counters.
  • 16-bit tick counter creates one second based on the crystal clock.
  • 4-bit fraction counter keeps track of the static crystal errors in one second that is less than one oscillator tick.
  • 32-bit seconds counter holds the real time and allows on-demand reload whenever current time of the RTC is set.
  • Allows wake-up at a specific second within the 136 years (32-bit alarm)

Missing features, Known Issues, limitations

  • None

Overview of Linux RTC Framework

http://lxr.free-electrons.com/source/Documentation/rtc.txt
This weblink is path to rtc.txt file in linux documentation which clearly expalins about the legacy and new framework for RTC on SoC.

Kernel Configuration:

Kconfig options:
Menuconfig snapshots -

Testing Procedure

Mainline status

This driver is currently in sync with the mainline kernel except for the following:

   rtc: zynqmp: Add calibration set and get support 

ChangeLog

  • 2020.2

    • summary:
      • rtc: zynqmp: Clear alarm interrupt status before interrupt enable
    • Commits
  • 2020.1

    • summary:
      • rtc: rtc-zynqmp: Add calibration set and get support
    • Commits
      • a4704c54 :Add calibration set and get support
  • 2019.2

    • Summary
      • rtc: rtc-zynqmp: Clear alarm interrupt status before intr enable
    • Commits
      • 771fb636 rtc: rtc-zynqmp: Clear alarm interrupt status before intr enable
  • 2019.1

    • None
  • 2018.3

    • None
  • 2018.2

    • None
  • 2018.1

    • None
  • 2017.4

    • None
  • 2017.3

    • None
  • 2017.2

    • None
  • 2017.1

    • None
  • 2016.3

    • None

Related Links

http://lxr.free-electrons.com/source/Documentation/rtc.txt