Re: [PATCH 7/9] dt-bindings: connector: Add PCIe M.2 Mechanical Key E connector

[Manivannan Sadhasivam]

On Wed, Nov 12, 2025 at 10:08:57PM +0200, Dmitry Baryshkov wrote:
> On Wed, Nov 12, 2025 at 08:15:19PM +0530, Manivannan Sadhasivam via B4 Relay wrote:
> > From: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxxxxxxxx>
> > 
> > Add the devicetree binding for PCIe M.2 Mechanical Key E connector defined
> > in the PCI Express M.2 Specification, r4.0, sec 5.1.2. This connector
> > provides interfaces like PCIe or SDIO to attach the WiFi devices to the
> > host machine, USB or UART+PCM interfaces to attach the Bluetooth (BT)
> > devices along with additional interfaces like I2C for NFC solution. At any
> > point of time, the connector can only support either PCIe or SDIO as the
> > WiFi interface and USB or UART as the BT 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.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxxxxxxxx>
> > ---
> >  .../bindings/connector/pcie-m2-e-connector.yaml    | 154 +++++++++++++++++++++
> >  MAINTAINERS                                        |   1 +
> >  2 files changed, 155 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/connector/pcie-m2-e-connector.yaml b/Documentation/devicetree/bindings/connector/pcie-m2-e-connector.yaml
> > new file mode 100644
> > index 0000000000000000000000000000000000000000..91cb56b1a75b7e3de3b9fe9a7537089f96875746
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/connector/pcie-m2-e-connector.yaml
> > @@ -0,0 +1,154 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/connector/pcie-m2-e-connector.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: PCIe M.2 Mechanical Key E Connector
> > +
> > +maintainers:
> > +  - Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxxxxxxxx>
> > +
> > +description:
> > +  A PCIe M.2 E connector node represents a physical PCIe M.2 Mechanical Key E
> > +  connector. Mechanical Key E connectors are used to connect Wireless
> > +  Connectivity devices including combinations of Wi-Fi, BT, NFC to the host
> > +  machine over interfaces like PCIe/SDIO, USB/UART+PCM, and I2C.
> > +
> > +properties:
> > +  compatible:
> > +    const: pcie-m2-e-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: PCIe/SDIO interface
> 
> The same comment as for the M-key bindings: please describe endpoints.
> 

Sure.

> > +  led1-gpios:
> > +    description: GPIO controlled connection to LED_1# signal. This signal is
> > +      used by the M.2 card to indicate the card status via the system mounted
> > +      LED. Refer, PCI Express M.2 Specification r4.0, sec 3.1.12.2 for more
> > +      details.
> 
> How are we supposed to handle these LEDs? I have been assuming that
> these pins should go striaght to the LED driver.
> 

Yes. I should just drop these.

> > +    maxItems: 1
> > +
> > +  led2-gpios:
> > +    description: GPIO controlled connection to LED_2# signal. This signal is
> > +      used by the M.2 card to indicate the card status via the system mounted
> > +      LED. Refer, PCI Express M.2 Specification r4.0, sec 3.1.12.2 for more
> > +      details.
> > +    maxItems: 1
> > +
> > +  viocfg-gpios:
> > +    description: GPIO controlled connection to IO voltage configuration
> > +      (VIO_CFG) signal. This signal is used by the M.2 card to indicate to the
> > +      host system that the card supports an independent IO voltage domain for
> > +      the sideband signals. Refer, PCI Express M.2 Specification r4.0, sec
> > +      3.1.15.1 for more details.
> > +    maxItems: 1
> 
> This more looks like viocfg-supply. Looking at this one and several
> other pins, it's more like a GPIO controller, providing those pins for
> the system, rather than a GPIO consumer.
> 

It is not a supply, but rather an indicator to the host. If it is low, then it
indicates that the card supports 3.3V on the sideband IO signals.

- Mani

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