linux-kernel - Re: [PATCH] clocksource: timer-tegra186: Enable WDT at probe

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Message-ID: <a0d7a8c6-af60-4f70-9d60-a87e0701bc91@nvidia.com>
Date: Thu, 3 Jul 2025 08:55:04 +0100
From: Jon Hunter <jonathanh@...dia.com>
To: Thierry Reding <thierry.reding@...il.com>,
 Kartik Rajput <kkartik@...dia.com>
Cc: daniel.lezcano@...aro.org, tglx@...utronix.de,
 linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH] clocksource: timer-tegra186: Enable WDT at probe



On 03/07/2025 07:55, Thierry Reding wrote:
> On Mon, Jun 30, 2025 at 04:31:35PM +0530, Kartik Rajput wrote:
>> Currently, if the system crashes or hangs during kernel boot before
>> userspace initializes and configures the watchdog timer, then the
>> watchdog won’t be able to recover the system as it’s not running. This
>> becomes crucial during an over-the-air update, where if the newly
>> updated kernel crashes on boot, the watchdog is needed to reset the
>> device and boot into an alternative system partition. If the watchdog
>> is disabled in such scenarios, it can lead to the system getting
>> bricked.
>>
>> Enable the WDT during driver probe to allow recovery from any crash/hang
>> seen during early kernel boot. Also, disable interrupts once userspace
>> starts pinging the watchdog.
>>
>> Signed-off-by: Kartik Rajput <kkartik@...dia.com>
>> ---
>>   drivers/clocksource/timer-tegra186.c | 42 ++++++++++++++++++++++++++++
>>   1 file changed, 42 insertions(+)
> 
> This seems dangerous to me. It means that if the operating system
> doesn't start some sort of watchdog service in userspace that pings the
> watchdog, the system will reboot 120 seconds after the watchdog probe.


I don't believe that will happen with this change. The kernel will 
continue to pet the watchdog until userspace takes over with this 
change. At least that is my understanding.

Jon

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