On 03/02/2023 03.15, Simon Glass wrote:
Hi Tom,
On Thu, 2 Feb 2023 at 10:22, Tom Rini trini@konsulko.com wrote:
Honestly, not really? Some good number of SoCs will start the watchdog in ROM and these are also the ones that don't allow you to turn it off.
I hope not, that sounds really risky. How would you debug such a platform?
_Every single_ custom piece of industrial (as opposed to consumer-grade) hardware I've worked on as a consultant has had an external, always-running, gpio-petted watchdog. It's simply just something that the hardware designers include, and in some cases that's even due to certification requirements. So an always-running, cannot-be-turned-off, watchdog is a real thing, in real hardware, and if specs don't account for that, well, the spec is just paper, and we can ignore it.
As for debugging and bringup, I've seen various solutions (depending on the actual watchdog chip). Usually there's some way to place a jumper that will either feed the watchdog from some, say, 32kHz output from an RTC or elsewhere, or place a jumper to pull up/pull down some enable/disable pin to the watchdog chip. IOW, when you have physical access to the PCB lying on your desk, you can disable the watchdog, but there's no way to do that in the field or in production.
Rasmus