linux-kernel - Re: [PATCH] ARM: dts: at91: enable watchdog for SAMA5D3 Xplained

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Message-ID: <fead1c9a-ac64-4445-9c8f-e5c8fa9b406a@bootlin.com>
Date:   Mon, 13 Dec 2021 17:02:12 +0100
From:   Michael Opdenacker <michael.opdenacker@...tlin.com>
To:     Nicolas Ferre <nicolas.ferre@...rochip.com>, robh+dt@...nel.org,
        alexandre.belloni@...tlin.com, ludovic.desroches@...rochip.com
Cc:     michael.opdenacker@...tlin.com, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: dts: at91: enable watchdog for SAMA5D3 Xplained

Hi Nicolas,

On 12/13/21 4:48 PM, Nicolas Ferre wrote:
> On 09/12/2021 at 16:45, Michael Opdenacker wrote:
>> Like on the SAMA5D2 and SAMA5D4 Xplained boards,
>> enable the watchdog device on the SAMA5D3 Xplained board.
>>
>> As explained on drivers/watchdog/at91sam9_wdt.c,
>> for the watchdog driver to work in Linux, you need to make sure
>> that the bootstrap / bootloader doesn't disable the watchdog,
>> as the Watchdog Timer Mode Register can be only written to once.
>>
>> Signed-off-by: Michael Opdenacker <michael.opdenacker@...tlin.com>
>
> Hi Michael,
>
> Thanks for your patch.
>
> Even if I understand the need for alignment with other sama5 SoCs, I'm
> not planning to take this patch to enable the watchdog by default.
>
> As you highlight, this older watchdog, compared to the ones on sama5d4
> or sama5d2, cannot be re-enabled.
> On our usual prebuilt demos and configurations, that don't have
> watchdog support by default, enabling it triggers the following errors:
> at91_wdt fffffe40.watchdog: watchdog is disabled
> at91_wdt: probe of fffffe40.watchdog failed with error -22
>
> I prefer to let the user enable the watchdog explicitly, on the whole
> chain of components for its use-case and make sure to "pet" it correctly.


Thanks for your review. I understand. It's your call anyway.
At least, this is documented through this discussion in the mailing list
archives :)
Cheers
Michael.

-- 
Michael Opdenacker, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com