Watchdog Timers Driver for Hard Processor System¶
Last updated: December 10, 2025
Upstream Status: Upstreamed
Device Supported: Agilex 5
Introduction¶
The watchdog timers are peripherals you can use to recover from system lockup that might be caused by software or system related issues. The hard processor system (HPS) provides five programmable watchdog timers, which are connected to the level 4 (L4) peripheral bus.
Each watchdog timer consists of a slave interface for control and status register (CSR) access, a register block, and a 32-bit down counter that operates on the slave interface clock (l4_sys_free_clk). A pause input, driven by the system manager, optionally pauses the counter when a CPU is being debugged.The watchdog timer drives an interrupt request to the MPU and a reset request to the reset manager.
For more information please refer to the Agilex 5 Hard Processor System Technical Reference Manual.
Driver Sources¶
The source code for this driver can be found at https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/watchdog/dw_wdt.c.
Driver Capabilities¶
- Allows configuration of the watchdog timer timeout period, specifying the duration after which the watchdog will trigger a system reset if not reset by the software
- Initializes the watchdog timer hardware during system boot, setting up the necessary registers and configurations to enable watchdog functionality.
- Handles interrupts generated by the watchdog timer hardware, allowing the system to respond appropriately to watchdog events, such as timer expiration.
Kernel Configurations¶
CONFIG_DW_WATCHDOG
Device Tree¶
Example Device tree location:
Test Procedures¶
This test procedure was exercised on Agilex 5 E-Series Premium Development Kit using the GSRD for HPS Enablement Board (booting from SD Card) from 24.3.1 release which uses Linux Kernel 6.6.51.
Step 1: Verify that the Watchdog Node is in the Device Tree¶
First, verify that the watchdog node is present in the device tree. You can do this by booting the system and running:
ls /proc/device-tree/soc\@0/watchdog*
/proc/device-tree/soc@0/watchdog@10d00200:
clocks compatible interrupts name phandle reg resets status
/proc/device-tree/soc@0/watchdog@10d00300:
clocks compatible interrupts name phandle reg resets status
/proc/device-tree/soc@0/watchdog@10d00400:
clocks compatible interrupts name phandle reg resets status
/proc/device-tree/soc@0/watchdog@10d00500:
clocks compatible interrupts name phandle reg resets status
/proc/device-tree/soc@0/watchdog@10d00600:
clocks compatible disable-over-current interrupts name phandle reg resets status
Read the status of the watchdog that is present.
You should see output indicating the presence of the watchdog node (The printout of the following cat command should be 'okay' as shown above)
Step 2: Check Watchdog Status¶
Next, check the status of the watchdog to ensure it is active. Run the following command:
ls /dev/watchdog*
/dev/watchdog /dev/watchdog1 /dev/watchdog3
/dev/watchdog0 /dev/watchdog2 /dev/watchdog4
Step 3: Test Watchdog Reset Functionality¶
To test the watchdog's ability to reset the system, you can disable the watchdog by writing to its control register. Run the following command:
After running this command, the system should reset within a few seconds. You will see the login prompt reappear after the reset.
Step 4: Verify System Recovery¶
Once the system has recovered from the reset, all the services and applications should run as expected.
Known Issues¶
None known
Notices & Disclaimers¶
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Created: May 25, 2024