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

  • Configurable timeout interval in seconds.
  • Reset on timeout can be selected.

Known Issues and Limitations

  • None.

Kernel Configuration

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

wdt.PNG


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

For Zynq7000:
Example: In ${PETALINUX_PROJECT}/components/plnx_workspace/device-tree/device-tree-generation/zynq-7000.dtsi
watchdog0: watchdog@f8005000 {
        clocks = <&clkc45>;
        compatible = "cdns,wdt-r1p2";
        interrupt-parent = <&intc>;
        interrupts = <0 9 1>;
        reg = <0xf8005000 0x1000>;
        timeout-sec = <10>;
};
 
Modify the device tree source in ${PETALINUX_PROJECT}/project-spec/meta-user/recipes-bsp/device-tree/files/system-user.dtsi as below and rebuild your project.
&watchdog0 {
    status = "okay";
};
If you 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;
};
For ZynqMP:
Example: In ${PETALINUX_PROJECT}/components/plnx_workspace/device-tree/device-tree-generation/zynqmp.dtsi
watchdog0: watchdog@fd4d0000 {
        compatible = "cdns,wdt-r1p2";
        status = disabled;
        interrupt-parent = <&gic>;
        interrupts = <0 113 1>;
        reg = <0x0 0xfd4d0000 0x1000>;
        timeout-sec = <10>;
};
 
Modify the device tree source in ${PETALINUX_PROJECT}/project-spec/meta-user/recipes-bsp/device-tree/files/system-user.dtsi as below and rebuild your project.
&watchdog0 {
    status = "okay";
};
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 ZynqMP so you need add PMU firmware in your BOOT.bin
&watchdog0 {
    status = "okay";
    reset-on-timeout;
};
Note: For 2017.1 or later petalinux ENABLE_EM needs to be enabled
Reference Link: http://www.wiki.xilinx.com/PetaLinux+Yocto+Tips (Section: How to patch PMU Firmware in v2017.1 PetaLinux project)

Test procedure

Note:
In case of zynqMP WDT 1 must be enabled at the h/w level.

Start the watchdog timer and see if it runs out without enabling reset.
echo s > /dev/watchdog0

Expected Output

//after 10 seconds

If reset-on-timeout property is present in the watchdog node
root@xilinx-zcu102-2017_4:~# dmesg |grep wdt
[    1.609408] cdns-wdt fd4d0000.watchdog: Xilinx Watchdog Timer at ffffff8008f2d000 with timeout 10s
root@xilinx-zcu102-2017_4:~#
root@xilinx-zcu102-2017_4:~# echo s > /dev/watchdog0
[   24.840197] watchdog: watchdog0: watchdog is still running!
root@xilinx-zcu102-2017_4:~#
root@xilinx-zcu102-2017_4:~#
root@xilinx-zcu102-2017_4:~# Xilinx Zynq MP First Stage Boot Loader
 
Release 2017.4   Feb 27 2018  -  13:18:55
NOTICE:  ATF running on XCZU9EG/silicon v4/RTL5.1 at 0xfffea000, with PMU firmware
NOTICE:  BL31: Secure code at 0x0
NOTICE:  BL31: Non secure code at 0x8000000
NOTICE:  BL31: v1.3(release):47af34b
 
Without reset-on-timeout property in the watchdog node
cdns-wdt fd4d0000.watchdog: Watchdog timed out.

Mainline Status

  • This driver is currently in sync with mainline kernel

Change Log

  • 2018.2
    • None
  • 2018.1
    • None
  • 2017.4
    • None
  • 2017.3
    • Summary
      • watchdog: cadence_wdt: Fix issue with timeout-sec dt property
      • watchdog: cadence_wdt: make of_device_ids const.
      • watchdog: cadence_wdt: Enable access to module parameters
      • watchdog: cadence_wdt: Show information when driver is probed
    • Commits
      • 33ca085 watchdog: cadence_wdt: Fix issue with timeout-sec dt property
      • e51604b watchdog: cadence_wdt: make of_device_ids const.
      • 98dde08 watchdog: cadence_wdt: Enable access to module parameters
      • cf698e7 watchdog: cadence_wdt: Show information when driver is probed
  • 2017.2
    • None
  • 2017.1
    • Summary
      • watchdog: cadence_wdt: Fix the suspend resume.
      • watchdog: constify watchdog_ops structures.

    • Commits
      • eadc4fe watchdog: cadence_wdt: Fix the suspend resume.
      • 85f15cf watchdog: constify watchdog_ops structures.

  • 2016.4
    • None
  • 2016.3
    • None

Related Links