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 13:52:58 -0800
From: Doug Anderson <dianders@...omium.org>
To: Stephen Boyd <swboyd@...omium.org>
Cc: Bjorn Andersson <andersson@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Guenter Roeck <linux@...ck-us.net>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 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

Hi,

On Mon, Nov 6, 2023 at 1:49 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> 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?

I like to make like to make typos. If you hadn't hadn't noticed.

I'll wait another few days and send a version with the typo fixed
unless Bjorn tells me not to (because he didn't care and applied it
anyway or because he fixed it himself while applying).


> > 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>

Thanks!

-Doug