linux-kernel - Re: [PATCH 2/2] watchdog: Add Apple SoC watchdog driver

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Message-Id: <0fc06d43-fcca-4cc5-a0e2-9a066bfb7702@www.fastmail.com>
Date:   Sat, 13 Nov 2021 12:19:35 +0100
From:   "Sven Peter" <sven@...npeter.dev>
To:     "Janne Grunau" <j@...nau.net>
Cc:     "Wim Van Sebroeck" <wim@...ux-watchdog.org>,
        "Guenter Roeck" <linux@...ck-us.net>,
        "Hector Martin" <marcan@...can.st>,
        "Alyssa Rosenzweig" <alyssa@...enzweig.io>,
        "Rob Herring" <robh+dt@...nel.org>,
        "Mark Kettenis" <mark.kettenis@...all.nl>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] watchdog: Add Apple SoC watchdog driver

Hi Janne,

On Sat, Nov 13, 2021, at 12:14, Janne Grunau wrote:
> On 2021-11-13 10:47:32 +0100, Sven Peter wrote:
>> Add support for the watchdog timer found in Apple SoCs. This driver is
>> also required to reboot these machines.
>
> Tested on a M1 Max with
> compatibe = "apple,t6000-wdt", "apple,wdt";
> MacOS 12 on the same machine does not use the watchdog for reset. MacOS 
> log output suggests that it uses a "pgmr" call for reset.
>
> Feel free to add
> Tested-by: Janne Grunau <j@...nau.net>

Awesome, thanks for testing this!
I suspect that they added an additional reset path for the Pro/Max variants.
On my M1 macOS seems to only use this watchdog to reset the machine.

And if I understand the linux reset infrastructure correctly it's still fine
to have this as a "fallback" reset notifier even on the Pro/Max and add support
for the proper "pmgr" reset notifier eventually with a higher priority. 


Best,

Sven