Introduction

This page gives an overview of the WDT driver which is available as part of the Zynq and ZynqMP Linux distribution and in the mainline.
Paths, files, links and documentation on this page are given relative to the Linux kernel source tree.

HW IP Features


Known Issues and Limitations


Kernel Configuration


The following config options should be enabled in order to build the wdt driver:
CONFIG_CADENCE_WATCHDOG
CONFIG_XILINX_WATCHDOG



Device tree and Build Configurations

For more details, please refer "Documentation/devicetree/bindings/watchdog/cadence-wdt.txt"

Zynq7000

  1. Zynq7000 platform device-tree can be found in https://github.com/Xilinx/device-tree-xlnx/blob/xlnx_rel_v2021.2/device_tree/data/kernel_dtsi/2021.2/zynq/zynq-7000.dtsi#L455-L462

    watchdog0: watchdog@f8005000 {
        clocks = <&clkc45>;
        compatible = "cdns,wdt-r1p2";
        interrupt-parent = <&&intc>;
        interrupts = <0 9 1>;
        reg = <0xf8005000 0x1000>;
        timeout-sec = <10>;
};


  2. Modify the device tree in <plnx-proj-root>/project-spec/meta-user/recipes-bsp/device-tree/files/system-user.dtsi as below and rebuild your project. 

    &watchdog0 {
    status = "okay";
};


  3. If user want the watchdog to trigger a software reset/reboot upon time out then add "reset-on-timeout" in device tree node.

    &watchdog0 {
    status = "okay";
    reset-on-timeout;
};


Zynq UltraScale+ MPSoC/RFSoC

  1. ZynqMP platform device-tree can be found in https://github.com/Xilinx/device-tree-xlnx/blob/xlnx_rel_v2021.2/device_tree/data/kernel_dtsi/2021.2/zynqmp/zynqmp.dtsi#L1043-L1051

    # timeout-sec value is set to 10s in 2018.2 and below release and 60s in 2018.3 and later release.
watchdog0: watchdog@fd4d0000 {
        compatible = "cdns,wdt-r1p2";
        status = disabled;
        interrupt-parent = <&gic>;
        interrupts = <0 113 1>;
        reg = <0x0 0xfd4d0000 0x1000>;
        timeout-sec = <60>;
};


  2. Modify the device tree source in <plnx-proj-root>/project-spec/meta-user/recipes-bsp/device-tree/files/system-user.dtsi as below and rebuild your project. 

    &watchdog0 {
    status = "okay";
};


  3. If user want the watchdog to trigger a software reset/reboot upon time out then add "reset-on-timeout" in device tree node. Software reset is handled in PMU firmware for Zynq UltraScale+ MPSoC/RFSoC so you need add PMU firmware elf packaged as part of BOOT.bin

    &watchdog0 {
    status = "okay";
    reset-on-timeout;
    timeout-sec = <10>;
};


  4.  For 2017.1 or later PetaLinux ENABLE_EM needs to be enabled from PMUFW, For more details refer PetaLinux Yocto Tips and PMU Firmware#PMUFWBuildFlags

    # For 2017.4 and below PetaLinux/Yocto release only
$ vim <plnx-proj-root>/project-spec/meta-user/recipes-bsp/pmu/pmu-firmware_%.bbappend
 
#For v2018.1 to v2020.2 PetaLinux/Yocto releases only
$ vim <plnx-proj-root>/project-spec/meta-user/recipes-bsp/pmu-firmware/pmu-firmware_%.bbappend

# For v2021.1 PetaLinux/Yocto releases only
$ vim <plnx-proj-root>/project-spec/meta-user/recipes-bsp/emebdeddedsw/pmu-firmware_%.bbappend

# For v2021.2 and later PetaLinux/Yocto releases only
$ vim <plnx-proj-root>/project-spec/meta-user/recipes-bsp/embeddedsw/pmu-firmware_%.bbappend


    # pmu-firmware_%.bbappend content
YAML_COMPILER_FLAGS_append = " -DENABLE_EM -DENABLE_SCHEDULER"


Test Procedure


In case of Zynq UltraScale+ MPSoC/RFSoC,  WDT 1 must be enabled in vivado design.


  1. Start the watchdog timer and see if it runs out without enabling reset.

    # echo s > /dev/watchdog0


  2. If reset-on-timeout and timeout-sec device-tree node property is enabled in watchdog node, then PMUFW will reset the system and expected output as shown below.

    PetaLinux 2018.2 xilinx-zcu102-2018_2 /dev/ttyPS0

xilinx-zcu102-2018_2 login: root
Password:
root@xilinx-zcu102-2018_2:~#
root@xilinx-zcu102-2018_2:~# dmesg | grep wdt
[    1.669543] cdns-wdt fd4d0000.watchdog: Xilinx Watchdog Timer at ffffff800913d000 with timeout 10s
root@xilinx-zcu102-2018_2:~#
root@xilinx-zcu102-2018_2:~# echo s > /dev/watchdog0
[   66.480417] watchdog: watchdog0: watchdog did not stop!
root@xilinx-zcu102-2018_2:~# Xilinx Zynq MP First Stage Boot Loader
Release 2018.2   Oct 31 2018  -  15:24:39
NOTICE:  ATF running on XCZU9EG/silicon v4/RTL5.1 at 0xfffea000
NOTICE:  BL31: Secure code at 0x0
NOTICE:  BL31: Non secure code at 0x10080000
NOTICE:  BL31: v1.4(release):xilinx-v2018.1-4-g93a69a5a
NOTICE:  BL31: Built : 21:21:00, Oct 31 2018
PMUFW:  v1.0


  3. If reset-on-timeout device-tree node property is not enabled in watchdog node, then PMUFW will not reset the system and expected output as shown below.

    cdns-wdt fd4d0000.watchdog: Watchdog timed out.



Mainline Status

watchdog: cadence: Use devm_clk_get_enabled() helper

Change Log

Related Links