linux-kernel - Re: [PATCH v3 1/4] dt-bindings: connector: Add PCIe M.2 Mechanical Key M connector

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Message-ID: <w773lfwggdemfitkwc2goh3odyzqo3vxbajzjlulum7i6trdsh@6izf6ajlr2ss>
Date: Sun, 28 Dec 2025 20:42:40 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Rob Herring <robh@...nel.org>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Bartosz Golaszewski <brgl@...ev.pl>, 
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, Stephan Gerhold <stephan.gerhold@...aro.org>, 
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, linux-pm@...r.kernel.org, Frank Li <Frank.Li@....com>
Subject: Re: [PATCH v3 1/4] dt-bindings: connector: Add PCIe M.2 Mechanical
 Key M connector

On Mon, Dec 08, 2025 at 01:11:10PM -0600, Rob Herring wrote:
> On Tue, Nov 25, 2025 at 04:42:26PM +0530, Manivannan Sadhasivam wrote:
> > Add the devicetree binding for PCIe M.2 Mechanical Key M connector defined
> > in the PCI Express M.2 Specification, r4.0, sec 5.3. This connector
> > provides interfaces like PCIe and SATA to attach the Solid State Drives
> > (SSDs) to the host machine along with additional interfaces like USB, and
> > SMB for debugging and supplementary features. At any point of time, the
> > connector can only support either PCIe or SATA as the primary host
> > interface.
> > 
> > The connector provides a primary power supply of 3.3v, along with an
> > optional 1.8v VIO supply for the Adapter I/O buffer circuitry operating at
> > 1.8v sideband signaling.
> > 
> > The connector also supplies optional signals in the form of GPIOs for fine
> > grained power management.
> > 
> > Reviewed-by: Frank Li <Frank.Li@....com>
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> > ---
> >  .../bindings/connector/pcie-m2-m-connector.yaml    | 141 +++++++++++++++++++++
> >  1 file changed, 141 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/connector/pcie-m2-m-connector.yaml b/Documentation/devicetree/bindings/connector/pcie-m2-m-connector.yaml
> > new file mode 100644
> > index 000000000000..f65a05d93735
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/connector/pcie-m2-m-connector.yaml
> > @@ -0,0 +1,141 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/connector/pcie-m2-m-connector.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: PCIe M.2 Mechanical Key M Connector
> > +
> > +maintainers:
> > +  - Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> > +
> > +description:
> > +  A PCIe M.2 M connector node represents a physical PCIe M.2 Mechanical Key M
> > +  connector. The Mechanical Key M connectors are used to connect SSDs to the
> > +  host system over PCIe/SATA interfaces. These connectors also offer optional
> > +  interfaces like USB, SMB.
> > +
> > +properties:
> > +  compatible:
> > +    const: pcie-m2-m-connector
> > +
> > +  vpcie3v3-supply:
> > +    description: A phandle to the regulator for 3.3v supply.
> > +
> > +  vpcie1v8-supply:
> > +    description: A phandle to the regulator for VIO 1.8v supply.
> > +
> > +  ports:
> > +    $ref: /schemas/graph.yaml#/properties/ports
> > +    description: OF graph bindings modeling the interfaces exposed on the
> > +      connector. Since a single connector can have multiple interfaces, every
> > +      interface has an assigned OF graph port number as described below.
> > +
> > +    properties:
> > +      port@0:
> > +        $ref: /schemas/graph.yaml#/properties/port
> > +        description: Host interfaces of the connector
> > +
> > +        properties:
> > +          endpoint@0:
> > +            $ref: /schemas/graph.yaml#/properties/endpoint
> > +            description: PCIe interface
> > +
> > +          endpoint@1:
> > +            $ref: /schemas/graph.yaml#/properties/endpoint
> > +            description: SATA interface
> 
> 
> Where's the binding changes to allow graph nodes on SATA and PCIe 
> bindings? I suppose Thunderbolt/USB4 on USB-C connectors will need that 
> too.
> 

Raised dtschema PR for PCI [1] and added SATA binding change in v4. For
Thunderbolt/USB4, there is no schema as of now. So skipping it until one gets
added.

[1] https://github.com/devicetree-org/dt-schema/pull/180

> > +
> > +        anyOf:
> > +          - required:
> > +              - endpoint@0
> > +          - required:
> > +              - endpoint@1
> > +
> > +      port@1:
> > +        $ref: /schemas/graph.yaml#/properties/port
> > +        description: USB 2.0 interface
> > +
> > +      port@2:
> > +        $ref: /schemas/graph.yaml#/properties/port
> > +        description: SMB interface
> 
> SMB is SMBus? There's no graph support for I2C either. For that, we use 
> 'i2c-parent'.
> 

Ack.

> > +
> > +    required:
> > +      - port@0
> > +
> > +  clocks:
> > +    description: 32.768 KHz Suspend Clock (SUSCLK) input from the host system to
> > +      the M.2 card. Refer, PCI Express M.2 Specification r4.0, sec 3.1.12.1 for
> > +      more details.
> > +    maxItems: 1
> > +
> > +  pedet-gpios:
> > +    description: GPIO controlled connection to PEDET signal. This signal is used
> 
> Instead of 'controlled connection' use just input or output. Arguably an 
> input isn't GPIO controlled.
> 

Ack.

- Mani

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