linux-kernel - Re: [PATCH v3 02/15] dt-bindings: display/msm/gmu: Add GMU wrapper

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Date:   Fri, 24 Feb 2023 12:50:14 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>
Cc:     linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Rob Clark <robdclark@...omium.org>
Subject: Re: [PATCH v3 02/15] dt-bindings: display/msm/gmu: Add GMU wrapper



On 24.02.2023 12:19, Krzysztof Kozlowski wrote:
> On 23/02/2023 13:06, Konrad Dybcio wrote:
>> GMU wrapper is essentially a register space within the GPU, which
>> Linux sees as a dumbed-down regular GMU: there's no clocks,
>> interrupts, multiple regs, iommus and OPP. Document it.
>>
>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>> ---
>>  .../devicetree/bindings/display/msm/gmu.yaml       | 49 ++++++++++++++++------
>>  1 file changed, 37 insertions(+), 12 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/display/msm/gmu.yaml b/Documentation/devicetree/bindings/display/msm/gmu.yaml
>> index ab14e81cb050..021373e686e1 100644
>> --- a/Documentation/devicetree/bindings/display/msm/gmu.yaml
>> +++ b/Documentation/devicetree/bindings/display/msm/gmu.yaml
>> @@ -19,16 +19,18 @@ description: |
>>  
>>  properties:
>>    compatible:
>> -    items:
>> -      - pattern: '^qcom,adreno-gmu-6[0-9][0-9]\.[0-9]$'
>> -      - const: qcom,adreno-gmu
>> +    oneOf:
>> +      - items:
>> +          - pattern: '^qcom,adreno-gmu-6[0-9][0-9]\.[0-9]$'
>> +          - const: qcom,adreno-gmu
>> +      - const: qcom,adreno-gmu-wrapper
> 
> Why wrapper is part of this binding then? Usually wrapper means there is
> wrapper node with a GMU child (at least this is what we call for all
> wrappers of custom IP blocks like USB DWC). Where is the child?
"GMU wrapper" is a sorta confusing name that Qualcomm chose for
the "fake GMU" which has the GMU_CX and GMU_GX registers responsible
for things like powering up some GPU things internally and some
perf/pwr counters. It is _not_ a wrapper in the sense of a parent-child
relationship. The GMU wrapper has no HFI (Hardware Firmware Interface)
to communicate through crafted messages, but relies on plain register
accesses.

Konrad
> 
> 
> Best regards,
> Krzysztof
>