linux-kernel - Re: [PATCH 2/6] dt-bindings: display: msm: gmu: add optional ocmem property

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Message-ID: <CAF6AEGs6By9-LGRBAPw2OwR9tRKJtEiZVgS2WVWRXmOK1VxNLA@mail.gmail.com>
Date:   Wed, 19 Jun 2019 13:21:20 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Brian Masney <masneyb@...tation.org>,
        Andy Gross <agross@...nel.org>,
        David Brown <david.brown@...aro.org>,
        Sean Paul <sean@...rly.run>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Marek <jonathan@...ek.ca>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 2/6] dt-bindings: display: msm: gmu: add optional ocmem property

On Wed, Jun 19, 2019 at 1:17 PM Rob Herring <robh+dt@...nel.org> wrote:
>
> On Sun, Jun 16, 2019 at 7:29 AM Brian Masney <masneyb@...tation.org> wrote:
> >
> > Some A3xx and A4xx Adreno GPUs do not have GMEM inside the GPU core and
> > must use the On Chip MEMory (OCMEM) in order to be functional. Add the
> > optional ocmem property to the Adreno Graphics Management Unit bindings.
> >
> > Signed-off-by: Brian Masney <masneyb@...tation.org>
> > ---
> >  Documentation/devicetree/bindings/display/msm/gmu.txt | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/display/msm/gmu.txt b/Documentation/devicetree/bindings/display/msm/gmu.txt
> > index 90af5b0a56a9..c746b95e95d4 100644
> > --- a/Documentation/devicetree/bindings/display/msm/gmu.txt
> > +++ b/Documentation/devicetree/bindings/display/msm/gmu.txt
> > @@ -31,6 +31,10 @@ Required properties:
> >  - iommus: phandle to the adreno iommu
> >  - operating-points-v2: phandle to the OPP operating points
> >
> > +Optional properties:
> > +- ocmem: phandle to the On Chip Memory (OCMEM) that's present on some Snapdragon
> > +         SoCs. See Documentation/devicetree/bindings/soc/qcom/qcom,ocmem.yaml.
>
> We already have a couple of similar properties. Lets standardize on
> 'sram' as that is what TI already uses.
>
> Also, is the whole OCMEM allocated to the GMU? If not you should have
> child nodes to subdivide the memory.
>

iirc, downstream a large chunk of OCMEM is statically allocated for
GPU.. the remainder is dynamically allocated for different use-cases.
The upstream driver Brian is proposing only handles the static
allocation case (and I don't think we have upstream support for the
various audio and video use-cases that used dynamic OCMEM allocation
downstream)

Although maybe we should still have a child node to separate the
statically and dynamically allocated parts?  I'm not sure what would
make the most sense..

BR,
-R