arm64: add a driver for the Apple watchdog

[kevans]

Summary

Ensure it's disarmed upon attach, provide basic reset functionality.

Register definitions/usage obtained from OpenBSD.

[emaste]

Would like a comment in the file mentioning what hardware this applies to

sys/arm64/apple/apple_wdog.c

6

Is this copy-paste from elsewhere? (Can we remove "All rights reserved."?)

[karels]

In D39824#906723, @emaste wrote:

Would like a comment in the file mentioning what hardware this applies to

Kyle, do you have any idea how to describe this? "Watchdog timer on Apple M1" is about all I know. We could mention t8103, but I don't know how accurate that is.

sys/arm64/apple/apple_wdog.c

6

It's from bcm2835_wdog.c, which has All Rights Reserved.

Should we mention the source in a comment?

[kevans]

In D39824#906730, @karels wrote:

In D39824#906723, @emaste wrote:

Would like a comment in the file mentioning what hardware this applies to

Kyle, do you have any idea how to describe this? "Watchdog timer on Apple M1" is about all I know. We could mention t8103, but I don't know how accurate that is.

Yeah, I think a simple: /* Watchdog timer on Apple Silicon machines */ is probably sufficient and accurate enough.

sys/arm64/apple/apple_wdog.c

6

CC @ray

[emaste]

sys/arm64/apple/apple_wdog.c

6

IMO it's worth having something like "based on bcm2835_wdog.c".

We can drop the "All rights reserved" (from this copy) if @karels and @ray agree

[karels]

sys/arm64/apple/apple_wdog.c

6

Fine with me; I wouldn't have included it except that it was in the earlier file.

[karels]

For what it's worth, I don't see problems with the driver, but I worked on the code (long ago), and don't know arm or watchdogs well enough to approve this. Someone else should approve.

[ray]

Look good to me. Thanks!

sys/arm64/apple/apple_wdog.c

6

Fine for me too.

[karels]

I had forgotten about this one... Kyle, can you remove "All rights reserved" and add the reference?

[kevans]

In D39824#921686, @karels wrote:

I had forgotten about this one... Kyle, can you remove "All rights reserved" and add the reference?

Yeah, I think I'll just tidy this up and push it from here. Thanks!

[bcr]

Is this review finished and can be closed?

[kevans]

In D39824#959982, @bcr wrote:

Is this review finished and can be closed?

negative; it hasn't landed yet, as I've been trying to get some consensus on some framework bits needed for the interrupt controller (I was hoping to push them at the same time).