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Zynqmp RTC

Zynqmp RTC

Owned by Confluence Wiki Admin (Unlicensed)
Last updated: May 28, 2025 by T, Harini

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:

config RTC_DRV_ZYNQMP tristate "Xilinx Zynq Ultrascale+ MPSoC RTC" depends on OF help If you say yes here you get support for the RTC controller found on Xilinx Zynq Ultrascale+ MPSoC.

Menuconfig snapshots -

[*] EDAC (Error Detection And Correction) reporting ---> [*] Real Time Clock ---> [*] DMA Engine support ---> [*] Auxiliary Display support --->



--- Real Time Clock [*] Set system time from RTC on startup and resume [*] Set the RTC time based on NTP synchronization (NEW) (rtc0) RTC used to set the system time [ ] RTC debug support *** RTC interfaces *** [*] /sys/class/rtc/rtcN (sysfs) [*] /proc/driver/rtc (procfs for rtcN) [*] /dev/rtcN (character devices) [ ] RTC UIE emulation on dev interface < > Test driver/device ........ *** Platform RTC drivers *** ........ < > ST M48T86/Dallas DS12887 < > ST M48T35 < > ST M48T59/M48T08/M48T02 < > Oki MSM6242 (NEW) < > TI BQ4802 < > Ricoh RP5C01 (NEW) < > EM Microelectronic V3020 <*> Xilinx Zynq Ultrascale+ MPSoC RTC (NEW) *** on-CPU RTC drivers ***

Testing Procedure

1.Get current date and time using "date" command 2.Set date and time using following commanddate -s "2015-09-08 13:36:00" 3. Verify the same using date command again.

Mainline status

This driver is currently in sync with the mainline kernel.

 

ChangeLog

  • 2025.1

    • Summary:

      • rtc: zynqmp: Fix optional clock name property

    • Commit:

  • 2024.2

    • None

  • 2024.1

    •  Summary

      • rtc: zynqmp: Convert to platform remove callback returning void

    • Commit

  • 2023.2

    • None

  • 2023.1

    • Summary

      • rtc: zynqmp: initialize fract_tick

    • Commit

Related Links

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

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