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Message-ID: <1d1bbc68-b484-4dc5-92f2-9454e8e2d6fb@collabora.com>
Date: Thu, 18 Apr 2024 09:43:02 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Rob Herring <robh@...nel.org>
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
Il 17/04/24 21:14, Rob Herring ha scritto:
> 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.
>
Okay, that's sensible - should've done that in v1 even. My bad.
Cheers
Angelo
> Rob
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