linux-kernel - Re: [PATCH v2 2/3] arm64: dts: qcom: hamoa: Add the APSS watchdog

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Message-ID: <3fcd274f-2502-4b3b-8a39-daf5e1938bed@oss.qualcomm.com>
Date: Fri, 19 Dec 2025 13:15:00 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Abel Vesa <abel.vesa@....qualcomm.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck
 <linux@...ck-us.net>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Rajendra Nayak <quic_rjendra@...cinc.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Cc: Stephan Gerhold <stephan.gerhold@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-watchdog@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] arm64: dts: qcom: hamoa: Add the APSS watchdog

On 12/19/25 11:00 AM, Abel Vesa wrote:
> The watchdog support in EL1 is SBSA compliant, handled by Gunyah
> hypervisor, but in EL2. the watchdog is an instance of the APSS WDT HW
> block, same as older platforms. So describe the APSS WDT node and mark
> it as reserved, as it will only be enabled in EL2 overlay.
> 
> Signed-off-by: Abel Vesa <abel.vesa@....qualcomm.com>
> ---
>  arch/arm64/boot/dts/qcom/hamoa.dtsi | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/hamoa.dtsi b/arch/arm64/boot/dts/qcom/hamoa.dtsi
> index a17900eacb20..b65dfad71c2f 100644
> --- a/arch/arm64/boot/dts/qcom/hamoa.dtsi
> +++ b/arch/arm64/boot/dts/qcom/hamoa.dtsi
> @@ -8302,6 +8302,14 @@ gic_its: msi-controller@...40000 {
>  			};
>  		};
>  
> +		apss_watchdog: watchdog@...10000 {
> +			compatible = "qcom,apss-wdt-x1e80100", "qcom,kpss-wdt";
> +			reg = <0x0 0x17410000 0x0 0x1000>;
> +			clocks = <&sleep_clk>;
> +			interrupts = <GIC_SPI 0 IRQ_TYPE_EDGE_RISING>;
> +			status = "reserved"; /* Accessible in EL2 only */

This is technically incorrect - it's not accessible if Gunyah is
present, which is only somewhat related - if you run a different
hypervisor which doesn't explicitly block access to this region, you
can still access it even though Linux may be running at EL1

Konrad