[FAQ] J721S2XSOMXEVM: How to enable main domain watchdog?

Hello,

Watchdog enabling needs 3 main modules:

1. Watchdog driver & DT nodes
2. SOC ESM
3. PMIC ESM

#2 & #3 are enabled in U-Boot.
#1 is enabled in Linux.

This is the wiring to route the Main domain ESM events(including watchdog) to PMIC.

So J721s2 has 3 instances of ESM. Main, MCU & WKUP domain ESM
respevtively. For the main domain ESM event to propagate to
PMIC the event needs to be routed via MCU ESM & then MCU ESM
needs to route the event to WKUP ESM & finally to PMIC.

MAIN ESM --> MCU ESM --> WKUP ESM --> PMIC.

Below is the patch set on top of 8.6 SDK U-Boot directory:

j721s2-u-boot-esm.tar

Steps to compile U-Boot with ESM support & install to SD card:

cd $PSDK_Linux/board-support/u-boot-2021.01+gitAUTOINC+62a9e51344-g62a9e51344
tar xvf j721s2-u-boot-esm.tar
git am j721s2-u-boot-esm/*
cd ../..
make u-boot
cp board-support/k3-image-gen-2022.01/tiboot3.bin board-support/u-boot_build/a72/tispl.bin board-support/u-boot_build/a72/u-boot.img /media/$USER/boot

Add the below diff to kernel to add the watchdog DTS nodes:

diff --git a/arch/arm64/boot/dts/ti/k3-j721s2-main.dtsi b/arch/arm64/boot/dts/ti/k3-j721s2-main.dtsi
index bd6b849fa..d79f98309 100644
--- a/arch/arm64/boot/dts/ti/k3-j721s2-main.dtsi
+++ b/arch/arm64/boot/dts/ti/k3-j721s2-main.dtsi
@@ -78,6 +78,24 @@
                };
        };
 
+       watchdog0: watchdog@2200000 {
+               compatible = "ti,j7-rti-wdt";
+               reg = <0x0 0x2200000 0x0 0x100>;
+               clocks = <&k3_clks 286 1>;
+               power-domains = <&k3_pds 286 TI_SCI_PD_EXCLUSIVE>;
+               assigned-clocks = <&k3_clks 286 1>;
+               assigned-clock-parents = <&k3_clks 286 5>;
+       };
+
+       watchdog1: watchdog@2210000 {
+               compatible = "ti,j7-rti-wdt";
+               reg = <0x0 0x2210000 0x0 0x100>;
+               clocks = <&k3_clks 287 1>;
+               power-domains = <&k3_pds 287 TI_SCI_PD_EXCLUSIVE>;
+               assigned-clocks = <&k3_clks 287 1>;
+               assigned-clock-parents = <&k3_clks 287 5>;
+       };
+

cd $PSDK_Linux/board-support/linux-5.10.162+gitAUTOINC+76b3e88d56-g76b3e88d56
"Apply the dts diff to add the watchdog nodes"
cd ../..
make linux-dtbs
sudo make linux-dtbs_install

With that the watchdog reset is functional.

Best Regards,
Keerthy