linux-kernel - Re: [PATCH 3/6] dt-bindings: display/msm/gmu: Document A612 RGMU

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Message-ID: <qcs6y22hozfmb2ipmahfw25m2xti2gr5kjn43c2woiueqe4xmd@ovnrhwibhhe2>
Date: Fri, 24 Oct 2025 12:28:24 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Akhil P Oommen <akhilpo@....qualcomm.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Rob Clark <robin.clark@....qualcomm.com>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>
Subject: Re: [PATCH 3/6] dt-bindings: display/msm/gmu: Document A612 RGMU

On Fri, Oct 24, 2025 at 04:33:28AM +0530, Akhil P Oommen wrote:
> On 10/22/2025 12:49 AM, Krzysztof Kozlowski wrote:
> > On 21/10/2025 17:51, Akhil P Oommen wrote:
> >> On 10/19/2025 2:43 PM, Krzysztof Kozlowski wrote:
> >>> On 17/10/2025 19:08, Akhil P Oommen wrote:
> >>>> RGMU a.k.a Reduced Graphics Management Unit is a small state machine
> >>>> with the sole purpose of providing IFPC (Inter Frame Power Collapse)
> >>>> support. Compared to GMU, it doesn't manage GPU clock, voltage
> >>>> scaling, bw voting or any other functionalities. All it does is detect
> >>>> an idle GPU and toggle the GDSC switch. As it doesn't access DDR space,
> >>>> it doesn't require iommu.
> >>>>
> >>>> So far, only Adreno 612 GPU has an RGMU core. Document RGMU in the GMU's
> >>>> schema.
> >>>>
> >>>> Signed-off-by: Akhil P Oommen <akhilpo@....qualcomm.com>
> >>>> ---
> >>>>  .../devicetree/bindings/display/msm/gmu.yaml       | 98 +++++++++++++++++-----
> >>>>  1 file changed, 79 insertions(+), 19 deletions(-)
> >>>>
> >>>> @@ -313,13 +360,26 @@ allOf:
> >>>>            items:
> >>>>              - const: gmu
> >>>>      else:
> >>>> -      required:
> >>>> -        - clocks
> >>>> -        - clock-names
> >>>> -        - interrupts
> >>>> -        - interrupt-names
> >>>> -        - iommus
> >>>> -        - operating-points-v2
> >>>> +      if:
> >>>> +        properties:
> >>>> +          compatible:
> >>>> +            contains:
> >>>> +              const: qcom,adreno-rgmu
> >>>> +      then:
> >>>> +        required:
> >>>> +          - clocks
> >>>> +          - clock-names
> >>>> +          - interrupts
> >>>> +          - interrupt-names
> >>>> +          - operating-points-v2
> >>>> +      else:
> >>>
> >>> No. Don't nest multiple ifs.
> >>
> >> I guess we should split this. I will add a 'required' constraint to the
> >> rgmu constraints above. And apply the below 'required' constraint
> >> specifically to 'qcom,adreno-gmu' instead of the 'else' fallback case.
> >>
> >> Please let me know if you have any suggestion.
> > 
> > Maybe the binding is getting to complicated and RGMU should have its own.
> 
> There is just a single chipset with RGMU and we haven't seen another one
> in the last 8 yrs. So it is very unlikely we will see another one again.
> So I feel it is not worth splitting this file just for RGMU.

I'd second the suggestion to split the RGMU schema. It's not about the
number of platforms supported by the file. It's about the clarity. I
think it would make the file easier to read.

> 
> Let me send another revision and let's take a call after that.

-- 
With best wishes
Dmitry