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

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Message-ID: <921d3a39-d95c-4156-b376-44e8dc6a6467@kernel.org>
Date: Wed, 16 Oct 2024 09:50:04 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Akhil P Oommen <quic_akhilpo@...cinc.com>
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 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.
> 
> 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.


Best regards,
Krzysztof