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Message-ID: <20240417191445.GB3101736-robh@kernel.org>
Date: Wed, 17 Apr 2024 14:14:45 -0500
From: Rob Herring <robh@...nel.org>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: djakov@...nel.org, krzysztof.kozlowski+dt@...aro.org,
conor+dt@...nel.org, matthias.bgg@...il.com, lgirdwood@...il.com,
broonie@...nel.org, keescook@...omium.org, gustavoars@...nel.org,
henryc.chen@...iatek.com, linux-pm@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-mediatek@...ts.infradead.org, kernel@...labora.com,
wenst@...omium.org, amergnat@...libre.com
Subject: Re: [PATCH v2 2/7] dt-bindings: interconnect: Add MediaTek EMI
Interconnect bindings
On Wed, Apr 17, 2024 at 05:32:54PM +0200, AngeloGioacchino Del Regno wrote:
> Il 17/04/24 16:54, Rob Herring ha scritto:
> > On Wed, Apr 17, 2024 at 11:14:37AM +0200, AngeloGioacchino Del Regno wrote:
> > > Add bindings for the MediaTek External Memory Interface Interconnect,
> > > which providers support system bandwidth requirements through Dynamic
> > > Voltage Frequency Scaling Resource Collector (DVFSRC) hardware.
> > >
> > > This adds bindings for MediaTek MT8183 and MT8195 SoCs.
> > >
> > > Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> > > ---
> > > .../interconnect/mediatek,mt8183-emi.yaml | 76 +++++++++++++++++++
> > > .../interconnect/mediatek,mt8183.h | 23 ++++++
> > > .../interconnect/mediatek,mt8195.h | 44 +++++++++++
> > > 3 files changed, 143 insertions(+)
> > > create mode 100644 Documentation/devicetree/bindings/interconnect/mediatek,mt8183-emi.yaml
> > > create mode 100644 include/dt-bindings/interconnect/mediatek,mt8183.h
> > > create mode 100644 include/dt-bindings/interconnect/mediatek,mt8195.h
> > >
> > > diff --git a/Documentation/devicetree/bindings/interconnect/mediatek,mt8183-emi.yaml b/Documentation/devicetree/bindings/interconnect/mediatek,mt8183-emi.yaml
> > > new file mode 100644
> > > index 000000000000..3ad60fd21f83
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/interconnect/mediatek,mt8183-emi.yaml
> > > @@ -0,0 +1,76 @@
> > > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/interconnect/mediatek,mt8183-emi.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: MediaTek External Memory Interface (EMI) Interconnect
> > > +
> > > +maintainers:
> > > + - AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> > > +
> > > +description: |
> > > + EMI interconnect providers support system bandwidth requirements through
> > > + Dynamic Voltage Frequency Scaling Resource Collector (DVFSRC) hardware.
> > > + The provider is able to communicate with the DVFSRC through Secure Monitor
> > > + Call (SMC).
> > > +
> > > + ICC provider ICC Nodes
> > > + ---- ----
> > > + _________ |CPU | |--- |VPU |
> > > + _____ | |----- ---- | ----
> > > + | |->| DRAM | ---- | ----
> > > + |DRAM |->|scheduler|----- |GPU | |--- |DISP|
> > > + | |->| (EMI) | ---- | ----
> > > + |_____|->|_________|---. ----- | ----
> > > + /|\ `-|MMSYS|--|--- |VDEC|
> > > + | ----- | ----
> > > + | | ----
> > > + | change DRAM freq |--- |VENC|
> > > + -------- | ----
> > > + SMC --> | DVFSRC | | ----
> > > + -------- |--- |IMG |
> > > + | ----
> > > + | ----
> > > + |--- |CAM |
> > > + ----
> > > +
> > > +properties:
> > > + compatible:
> > > + enum:
> > > + - mediatek,mt8183-emi
> > > + - mediatek,mt8195-emi
> > > +
> > > + reg:
> > > + maxItems: 1
> > > +
> > > + '#interconnect-cells':
> > > + const: 1
> > > +
> > > +required:
> > > + - compatible
> > > + - '#interconnect-cells'
> > > +
> > > +unevaluatedProperties: false
> > > +
> > > +examples:
> > > + - |
> > > + #include <dt-bindings/interconnect/mediatek,mt8195.h>
> > > +
> > > + soc {
> > > + #address-cells = <2>;
> > > + #size-cells = <2>;
> > > +
> > > + system-controller@...12000 {
> > > + compatible = "mediatek,mt8195-dvfsrc";
> > > + reg = <0 0x10012000 0 0x1000>;
> > > + #address-cells = <1>;
> > > + #size-cells = <0>;
> > > +
> > > + emi_icc: interconnect@1 {
> > > + compatible = "mediatek,mt8195-emi";
> > > + reg = <1>;
> > > + #interconnect-cells = <1>;
> >
> >
> > There's not really any need for this node. Just put #interconnect-cells
> > in the parent.
> >
>
> Actually, I modeled it to be a subnode of the DVFSRC for multiple reasons:
>
> 1. Some SoCs have more than one interconnect on the DVFSRC (two different kinds
> of EMI interconnect, and then also a SMI interconnect); and
>
> 2. Some boards will want to not enable the interconnect driver because some of
> those are not battery powered (so they just keep the knobs at full thrust
> from the bootloader and never care scaling busses); and
>
> 3. Some DVFSRC interconnect features may depend on firmware (but I'm not
> sure which ones and which SoCs, as there are lots of SMI/EMI ICC things that
> are not implemented yet with this series).
>
> The alternative would've been to add a property to enable, or disable, the SMI ICC
> (not present in this series), and/or one, or the other kind of EMI ICC (this series
> implements only the simpler EMI ICC, and I keep saying "the other" because I
> currently don't remember the name).... which is really ugly.
>
> Ideas? :-)
Just provide that reasoning in the commit msg.
Rob
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