linux-hardening - Re: [PATCH 1/9] arm64: dts: qcom: sc7180: Make watchdog bark interrupt edge triggered

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Date: Mon, 6 Nov 2023 13:49:04 -0800
From: Stephen Boyd <swboyd@...omium.org>
To: Bjorn Andersson <andersson@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Douglas Anderson <dianders@...omium.org>, Guenter Roeck <linux@...ck-us.net>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc: linux-watchdog@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	Rob Herring <robh+dt@...nel.org>, Wim Van Sebroeck <wim@...ux-watchdog.org>, 
	Andy Gross <agross@...nel.org>, "Guilherme G. Piccoli" <gpiccoli@...lia.com>, 
	Kees Cook <keescook@...omium.org>, Sai Prakash Ranjan <quic_saipraka@...cinc.com>, 
	Tony Luck <tony.luck@...el.com>, cros-qcom-dts-watchers@...omium.org, 
	devicetree@...r.kernel.org, linux-hardening@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/9] arm64: dts: qcom: sc7180: Make watchdog bark
 interrupt edge triggered

Quoting Douglas Anderson (2023-11-03 16:34:27)
> On sc7180 when the watchdog timer fires your logs get filled with:
>   watchdog0: pretimeout event
>   watchdog0: pretimeout event
>   watchdog0: pretimeout event
>   ...
>   watchdog0: pretimeout event
>
> If you're using console-ramoops to debug crashes the above gets quite
> annoying since it blows away any other log messages that might have
> been there.
>
> The issue is that the "bark" interrupt (AKA the "pretimeout"
> interrupt) remains high until the watchdog is pet. Since we've got
> things configured as "level" triggered we'll keep getting interrupted
> over and over.
>
> Let's switch to edge triggered. Now we'll get one interrupt when the
> "bark" interrupt goes off we'll get one interrupt and won't get

"We'll get one" twice?

> another one until the "bark" interrupt is cleared and asserts again.
>
> This matches how many older Qualcomm SoCs have things configured.
>
> Fixes: 28cc13e4060c ("arm64: dts: qcom: sc7180: Add watchdog bark interrupt")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---

Reviewed-by: Stephen Boyd <swboyd@...omium.org>