linux-kernel - Re: [PATCH v2] arm64: dts: mt8173-oak: Switch to SMC watchdog

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Date:   Thu, 28 Jul 2022 13:21:42 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Pin-yen Lin <treapking@...omium.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Eizan Miyamoto <eizan@...omium.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Evan Benn <evanbenn@...omium.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH v2] arm64: dts: mt8173-oak: Switch to SMC watchdog

Il 27/07/22 11:40, Pin-yen Lin ha scritto:
> Switch to SMC watchdog because we need direct control of HW watchdog
> registers from kernel. The corresponding firmware was uploaded in
> https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405.
> 
> Signed-off-by: Pin-yen Lin <treapking@...omium.org>
> ---
> 
> Changes in v2:
> - Move the modifications to mt8173-elm.dtsi and add some comments.
> 
>   arch/arm64/boot/dts/mediatek/mt8173-elm.dtsi | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/mediatek/mt8173-elm.dtsi b/arch/arm64/boot/dts/mediatek/mt8173-elm.dtsi
> index e21feb85d822..b2269770abc3 100644
> --- a/arch/arm64/boot/dts/mediatek/mt8173-elm.dtsi
> +++ b/arch/arm64/boot/dts/mediatek/mt8173-elm.dtsi
> @@ -161,6 +161,18 @@ hdmi_connector_in: endpoint {
>   			};
>   		};
>   	};
> +
> +	soc {
> +		/*
> +		 * Disable the original MMIO watch dog and switch to the SMC watchdog,
> +		 * which operates on the same MMIO.
> +		 */
> +		/delete-node/ watchdog@...07000;

Unfortunately, we're not quite there yet.
The comment is fine, but...

There's no need to /delete-node/: you can just do it like

/*
  * Disable the original MMIO watch dog and switch to the SMC watchdog,
  * which operates on the same MMIO.
  */
&watchdog {
	status = "disabled";
};

and...

> +
> +		watchdog {

This isn't addressable, hence it belongs to the root node, not to soc.
If you did that because of naming issues, I would propose to call it
smc-watchdog instead of watchdog.


> +			compatible = "arm,smc-wdt";

P.S.: No timeout-sec?

Regards,
Angelo

> +		};
> +	};
>   };
>   
>   &mfg_async {
>