linux-kernel - Re: [PATCH 2/3] arm64: dts: qcom: sm8550: Add tz-log node

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Message-ID: <20260209171128.GC1401643-robh@kernel.org>
Date: Mon, 9 Feb 2026 11:11:28 -0600
From: Rob Herring <robh@...nel.org>
To: Aaron Kling <webgeek1234@...il.com>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Kumar Sharma <quic_vksharma@...cinc.com>,
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, Lei Chen <quic_chenlei@...cinc.com>
Subject: Re: [PATCH 2/3] arm64: dts: qcom: sm8550: Add tz-log node

On Mon, Feb 02, 2026 at 10:25:23PM -0600, Aaron Kling wrote:
> On Fri, Jan 30, 2026 at 4:59 AM Konrad Dybcio
> <konrad.dybcio@....qualcomm.com> wrote:
> >
> > On 1/29/26 8:46 AM, Aaron Kling via B4 Relay wrote:
> > > From: Lei Chen <quic_chenlei@...cinc.com>
> > >
> > > Add DT node to enable tz-log driver.
> > >
> > > Signed-off-by: Lei Chen <quic_chenlei@...cinc.com>
> > > Signed-off-by: Aaron Kling <webgeek1234@...il.com>
> > > ---
> >
> > It's nice that you preserved the original authorship.
> >
> > Please extend the rather lackluster commit message to explain the
> > "why", which is notably different from the original downstream
> > addition, since your goal here is to mainly appease a grumpy
> > bootloader.
> >
> > >  arch/arm64/boot/dts/qcom/sm8550.dtsi | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > >
> > > diff --git a/arch/arm64/boot/dts/qcom/sm8550.dtsi b/arch/arm64/boot/dts/qcom/sm8550.dtsi
> > > index e3f93f4f412ded9583a6bc9215185a0daf5f1b57..740e3c238e8ed0f162dd168291f6e307ace66e80 100644
> > > --- a/arch/arm64/boot/dts/qcom/sm8550.dtsi
> > > +++ b/arch/arm64/boot/dts/qcom/sm8550.dtsi
> > > @@ -5136,6 +5136,14 @@ data-pins {
> > >                       };
> > >               };
> > >
> > > +             qcom_tzlog: tz-log@...aa720 {
> >
> > If we were to implement qcom,tz-log upstream, this would definitely
> > not be a node randomly in the middle of /soc, rather a child of
> > imem, most likely.
> >
> > Could you please check whether adding a qcom_tzlog label to *any*
> > node makes the BL happy enough? Does it need the properties that
> > this node has?
> 
> It does appear that ABL doesn't care about the path name, only the
> label. And given that the original change that worked had the label
> pointing at an empty node, it doesn't fail if all the properties are
> missing. I moved the node underneath an sram node and the bootloader
> loaded my dtbo just fine.
> 
> The imem/sram node, though... The numbers don't add up. Per the
> downstream dt, qcom,msm-imem@...aa000 has size 0x1000. Then
> tz-log@...AA720 has size 0x3000. Which... starts within the imem
> range, then blasts quite far outside of it. So... what should this end
> up looking like?
> 
> I should also note that an empty node at /soc@...z-log fails dt schema
> checks. I presume that adding any warnings would immediately get a
> patch nuked from orbit, which is why I fetched a real binding and node
> from CLO.

That's simply because tz-log has no addresss but is on a MMIO bus. Can't 
you just do:

/{
  qcom_tzlog: tz-log {};
};

With some note explaining the stupidity.

Rob