3.2.2.22. Watchdog
Watchdog Driver Overview
This guide covers K3 RTI-Windowed Watchdog Timer (WWDT) driver. It supports watchdogs found on TI’s AM64x SoCs.
The digital windowed watchdog opens a configurable time window in which the watchdog must be serviced. Any attempt to service the watchdog outside this time window, or a failure to service the watchdog in this time window, will cause the watchdog to generate an interrupt to the MCU ESM module. The MCU ESM module recieves these watchdog interrupts and triggers the reset logic to reset the device.
3.2.2.22.1. Driver Configuration
Driver source location:
drivers/watchdog/rti_wdt.cWatchdog module timeout parameter name: heartbeat
Watchdog module timeout parameter value, in seconds: from 1 to 1000 (default 60)
3.2.2.22.1.1. How to change timeout as kernel module parameter
The default timeout value can be changed the following way as kernel module parameter:
root@<machine>:~# lsmod | grep rti
rti_wdt 12288 0
root@<machine>:~# rmmod rti_wdt
root@<machine>:~# modprobe rti_wdt heartbeat=30
The above command changes the timeout from 60s to 30s
3.2.2.22.1.2. How to change timeout using DT property
Watchdog timeout can only be changed modprobe or insmod commands as shown above, this is the default in rti_wdt.c driver, to change using DT parameter timeout-sec, apply the diff below for am62x:
diff --git a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
index 066a82d2d4b8..ab7a5cb0571e 100644
--- a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
+++ b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
@@ -952,6 +952,7 @@ main_rti0: watchdog@e000000 {
power-domains = <&k3_pds 125 TI_SCI_PD_EXCLUSIVE>;
assigned-clocks = <&k3_clks 125 0>;
assigned-clock-parents = <&k3_clks 125 2>;
+ timeout-sec = <30>;
};
main_rti1: watchdog@e010000 {
diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
index 79e573bc7e4d..359db4f47b81 100644
--- a/drivers/watchdog/rti_wdt.c
+++ b/drivers/watchdog/rti_wdt.c
@@ -353,7 +353,8 @@ static int rti_wdt_probe(struct platform_device *pdev)
memunmap(vaddr);
}
- watchdog_init_timeout(wdd, heartbeat, dev);
+ wdd->timeout = heartbeat;
+ watchdog_init_timeout(wdd, 0, dev);
ret = watchdog_register_device(wdd);
if (ret) {
In the above example, timeout is set to 30s using timeout-sec DT property.
The DTS fixup is for am62x, but the same line could be applied to any watchdog node using the rti_wdt.c driver. The method to tell if a watchdog is using this driver is by looking at the compatible string:
compatible = "ti,j7-rti-wdt";
The driver diff can be applied directly for all platforms.
3.2.2.22.2. Kernel Configuration
Configs to be enabled in kernel:
Device Drivers --->
<*> Watchdog Timer Support --->
<*> Texas Instruments K3 RTI watchdog
Device tree configuration example
From k3-am64-main.dtsi:
main_rti0: watchdog@e000000 {
compatible = "ti,j7-rti-wdt";
reg = <0x00 0x0e000000 0x00 0x100>;
clocks = <&k3_clks 125 0>;
power-domains = <&k3_pds 125 TI_SCI_PD_EXCLUSIVE>;
assigned-clocks = <&k3_clks 125 0>;
assigned-clock-parents = <&k3_clks 125 2>;
};
3.2.2.22.3. Driver Usage
Once the driver is probed, each of watchdogs are exposed as a character device file by the kernel to be used by userspace:
/dev/watchdogX X - watchdog number (zero indexed)
How to test watchdog
An example of how to use them from a userspace application can be found in Linux Kernel at: samples/watchdog/watchdog-simple.c.