linux-kernel - Re: [PATCH 5/5] ARM: dts: qcom: msm8974: add interconnect nodes

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Date:   Wed, 23 Oct 2019 08:47:53 -0400
From:   Brian Masney <masneyb@...tation.org>
To:     Georgi Djakov <georgi.djakov@...aro.org>
Cc:     agross@...nel.org, bjorn.andersson@...aro.org, robh+dt@...nel.org,
        mark.rutland@....com, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 5/5] ARM: dts: qcom: msm8974: add interconnect nodes

On Wed, Oct 23, 2019 at 02:50:19PM +0300, Georgi Djakov wrote:
> On 13.10.19 г. 11:08 ч., Brian Masney wrote:
> > Add interconnect nodes that's needed to support bus scaling.
> > 
> > Signed-off-by: Brian Masney <masneyb@...tation.org>
> > ---
> >  arch/arm/boot/dts/qcom-msm8974.dtsi | 60 +++++++++++++++++++++++++++++
> >  1 file changed, 60 insertions(+)
> > 
> > diff --git a/arch/arm/boot/dts/qcom-msm8974.dtsi b/arch/arm/boot/dts/qcom-msm8974.dtsi
> > @@ -1152,6 +1207,11 @@
> >  				              "core",
> >  				              "vsync";
> >  
> > +				interconnects = <&mmssnoc MNOC_MAS_GRAPHICS_3D &bimc BIMC_SLV_EBI_CH0>,
> > +				                <&ocmemnoc OCMEM_VNOC_MAS_GFX3D &ocmemnoc OCMEM_SLV_OCMEM>;
> 
> Who will be the requesting bandwidth to DDR and ocmem? Is it the display or GPU
> or both? The above seem like GPU-related interconnects, so maybe these
> properties should be in the GPU DT node.

The display is what currently requests the interconnect path,
specifically mdp5_setup_interconnect() in
drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c. The Freedreno GPU bindings
currently don't have interconnect support. Maybe this is something that
I should add to that driver as well?

> > +				interconnect-names = "mdp0-mem",
> > +				                     "mdp1-mem";
> 
> As the second path is not to DDR, but to ocmem, it might be better to call it
> something like "gpu-ocmem".

I used what mdp5_kms.c expected.

Brian