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

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Message-ID: <c7334b38-3d6e-4fbf-a385-40551fbb7c93@oss.qualcomm.com>
Date: Fri, 24 Oct 2025 19:40:35 +0530
From: Akhil P Oommen <akhilpo@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Krzysztof Kozlowski <krzk@...nel.org>
Cc: 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 10/24/2025 2:58 PM, Dmitry Baryshkov wrote:
> 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.

Alright. If there is a general consensus, we can split out RGMU schema
to a new file.

-Akhil

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