TDA4VH-Q1: J784S4 Watchdog Usage – Examples, Servicing, Reset Configuration & Timer Precision

Akhil

Part Number: TDA4VH-Q1

Hello TI,

I am referring the post [FAQ] J784S4XEVM: How to enable main domain watchdog? - Processors forum - Processors - TI E2E support forums

We have a few questions regarding watchdog usage in both MAIN and MCU domains. We would appreciate guidance and references.

1. Example Programs

Could you please share sample implementations demonstrating watchdog usage for:

MAIN domain from A72
MAIN domain from Main R5F
MCU domain from MCU R5F

2. Watchdog Servicing

What is the recommended method to service the watchdog?

3. Timer Precision & Limits

What is the watchdog clock source?
What is the tick resolution / granularity?
What is the minimum programmable timeout of the watchdog?

4. Watchdog reset

Is it possible to reset the Main domain alone?

Thank you in advance for your support.

4 months ago

0 Keerthy J 4 months ago

TI__Guru**** 171280 points

Hello Akhil,

Which OS are you using? Is it linux or rtos?

Akhil said:

Is it possible to reset the Main domain alone?

No we have enabled full soc reset. Only main domain reset will need some external entity to load firmware on main domain Cores. Mcu domain r5f does not support that.

What's the use case that's being addressed here?

Best regards,

Keerthy

0 Akhil 4 months ago in reply to Keerthy J

Prodigy 60 points

We are running Linux on A72.

Regarding the Main domain reset use case:

We are referring section 5.70 in the safety manual.

0 Keerthy J 4 months ago

TI__Guru**** 171280 points

Hello Akhil,

Akhil said:
MAIN domain from A72

MAIN domain from Main R5F

MCU domain from MCU R5F

All 3 can be triggered from Linux using touch /dev/watchdog

Akhil said:
What is the recommended method to service the watchdog?

You can use user space scripts to pet the watchdog on a periodic basis. The default is 60S timeout in Linux kernel. You should pet the watchdog in < 60S everytime.

Something like:

while true; do echo 'V' > /dev/watchdog; sleep 10; done

Sleep 10 can be 50 if the default value is 60S timeout.

Akhil said:
What is the watchdog clock source?

What is the tick resolution / granularity?

What is the minimum programmable timeout of the watchdog?

k3conf dump clock 367

The above command will give you the clock source for MCU_RTI0 on your system. Refer: https://software-dl.ti.com/tisci/esd/09_02_07/5_soc_doc/j784s4/clocks.html

Akhil said:
What is the minimum programmable timeout of the watchdog?


The Linux default is 60S. You should be able to configure that to lower value. Minimum value is something I need to check.

- Keerthy