linux-kernel - Re: [PATCH RFC 3/3] arm64: dts: qcom: x1e80100: Add ACD levels for GPU

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Message-ID: <20241017061217.mmq27egyg5cdlubb@hu-akhilpo-hyd.qualcomm.com>
Date: Thu, 17 Oct 2024 11:42:17 +0530
From: Akhil P Oommen <quic_akhilpo@...cinc.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
CC: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        "Konrad
 Dybcio" <konradybcio@...nel.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, "Simona
 Vetter" <simona@...ll.ch>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon
	<nm@...com>,
        Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        <linux-pm@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH RFC 3/3] arm64: dts: qcom: x1e80100: Add ACD levels for
 GPU

On Wed, Oct 16, 2024 at 09:50:04AM +0200, Krzysztof Kozlowski wrote:
> On 15/10/2024 21:35, Akhil P Oommen wrote:
> > On Mon, Oct 14, 2024 at 09:40:13AM +0200, Krzysztof Kozlowski wrote:
> >> On Sat, Oct 12, 2024 at 01:59:30AM +0530, Akhil P Oommen wrote:
> >>> Update GPU node to include acd level values.
> >>>
> >>> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
> >>> ---
> >>>  arch/arm64/boot/dts/qcom/x1e80100.dtsi | 11 ++++++++++-
> >>>  1 file changed, 10 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/arch/arm64/boot/dts/qcom/x1e80100.dtsi b/arch/arm64/boot/dts/qcom/x1e80100.dtsi
> >>> index a36076e3c56b..e6c500480eb1 100644
> >>> --- a/arch/arm64/boot/dts/qcom/x1e80100.dtsi
> >>> +++ b/arch/arm64/boot/dts/qcom/x1e80100.dtsi
> >>> @@ -3323,60 +3323,69 @@ zap-shader {
> >>>  			};
> >>>  
> >>>  			gpu_opp_table: opp-table {
> >>> -				compatible = "operating-points-v2";
> >>> +				compatible = "operating-points-v2-adreno";
> >>
> >> This nicely breaks all existing users of this DTS. Sorry, no. We are way
> >> past initial bringup/development. One year past.

How do I identify when devicetree is considered stable? An arbitrary
time period doesn't sound like a good idea. Is there a general consensus
on this?

X1E chipset is still considered under development at least till the end of this
year, right?

> > 
> > It is not obvious to me how it breaks backward compatibility. Could you
> 
> I did not say "backward compatibility". I said existing users.
> 
> > please elaborate a bit? I am aware that drivers should be backward
> > compatible with DT, but not the other way. Are we talking about kernels other
> > than Linux?
> > 
> 
> Boot OpenBSD with new DTS. Previously: worked fine. Now: works less fine.
> 
> We had exact talk about this during LPC.
> 
> > Also, does including "operating-points-v2" too here help?
> 
> Fallback? Yes, assuming these are compatible. Not much is explained in
> the commit msg, except duplicating diff. That's not what the commit msg
> is for.

Okay. We can keep the fallback compatible string.

-Akhil.

> 
> 
> Best regards,
> Krzysztof
>