linux-kernel - Re: [PATCH v2 2/2] clocksource/drivers/timer-tegra186: fix watchdog self-pinging.

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Date: Sat, 24 Feb 2024 07:42:55 +0800
From: Pohsun Su <pohsuns@...dia.com>
To: <thierry.reding@...il.com>, <daniel.lezcano@...aro.org>,
	<tglx@...utronix.de>, <jonathanh@...dia.com>
CC: <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
	<sumitg@...dia.com>, Pohsun Su <pohsuns@...dia.com>
Subject: Re: [PATCH v2 2/2] clocksource/drivers/timer-tegra186: fix watchdog self-pinging.

> On Fri Feb 16, 2024 at 10:02 PM CET, Pohsun Su wrote:
>> This change removes watchdog self-pinging behavior.
>>
>> The timer irq handler is triggered due to the 1st expiration,
>> the handler disables and enables watchdog but also implicitly
>> clears the expiration count so the count can only be 0 or 1.
>>
>> Since this watchdog supports opened, configured, or pinged by
>> systemd, We remove this behavior or the watchdog may not bark
>> when systemd crashes since the 5th expiration never comes.
>>
>> Signed-off-by: Pohsun Su <pohsuns@...dia.com>
>> ---
>>  drivers/clocksource/timer-tegra186.c | 27 ++-------------------------
>>  1 file changed, 2 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/clocksource/timer-tegra186.c b/drivers/clocksource/timer-tegra186.c
>> index 8f516366da86..acff97da138a 100644
>> --- a/drivers/clocksource/timer-tegra186.c
>> +++ b/drivers/clocksource/timer-tegra186.c
>> @@ -175,7 +175,8 @@ static void tegra186_wdt_enable(struct tegra186_wdt *wdt)
>>                value |= WDTCR_PERIOD(1);
>> 
>>                /* enable local interrupt for WDT petting */
>> -             value |= WDTCR_LOCAL_INT_ENABLE;
>> +             if (0)
>> +                     value |= WDTCR_LOCAL_INT_ENABLE;
>
> We probably shouldn't proliferate this scheme. In retrospect I should've
> removed the two other similar blocks back when I submitted the driver at
> the time since they don't really serve a purpose. The intention at the
> time was to keep them there and eventually replace the condition with
> something that could actually be toggled, but it's been almost four
> years and this hasn't happened, so I suspect that we just don't need it
> at all. So perhaps you could remove this line along with the comment in
> this patch and then add another patch that removes the other unused bits
> so that we don't carry around stuff that we just never use.
> 
> Thierry

Sure, removing both lines and the comment above.
will add another patch to clean unused bits.

Thanks!
--
Pohsun