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

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Message-ID: <qiwgnela4b6gbwuuq7xaqjong47c2ix6caagjl6ryqukzqkswn@6l7rvkf4dfyx>
Date: Thu, 13 Nov 2025 10:30:42 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Frank Li <Frank.li@....com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>, 
	Rob Herring <robh@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Jiri Slaby <jirislaby@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
	Nicolas Schier <nicolas.schier@...ux.dev>, Hans de Goede <hansg@...nel.org>, 
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, Mark Pearson <mpearson-lenovo@...ebb.ca>, 
	"Derek J. Clark" <derekjohn.clark@...il.com>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Marcel Holtmann <marcel@...tmann.org>, 
	Luiz Augusto von Dentz <luiz.dentz@...il.com>, Bartosz Golaszewski <brgl@...ev.pl>, 
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org, 
	platform-driver-x86@...r.kernel.org, linux-pci@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, linux-bluetooth@...r.kernel.org, linux-pm@...r.kernel.org, 
	Stephan Gerhold <stephan.gerhold@...aro.org>, Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Subject: Re: [PATCH 7/9] dt-bindings: connector: Add PCIe M.2 Mechanical Key
 E connector

On Wed, Nov 12, 2025 at 12:11:56PM -0500, Frank Li wrote:
> On Wed, Nov 12, 2025 at 08:15:19PM +0530, Manivannan Sadhasivam wrote:
> > 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@....qualcomm.com>
> > ---
> >  .../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@....qualcomm.com>
> > +
> > +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
> 
> 
> PCIe and SDIO is difference signal at key E. why combine to one port? The
> similar case is USB2.0/UART
> 

They will be defined as separate endpoints in the next version.

> > +
> > +      port@1:
> > +        $ref: /schemas/graph.yaml#/properties/port
> > +        description: USB 2.0/UART interface
> > +
> > +      port@2:
> > +        $ref: /schemas/graph.yaml#/properties/port
> > +        description: PCM/I2S interface
> > +
> > +      port@3:
> > +        $ref: /schemas/graph.yaml#/properties/port
> > +        description: I2C interface
> > +
> > +    oneOf:
> > +      - 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
> 
> Do we need add pciref clock here?
> 
> > +
> > +  w_disable1-gpios:
> 
> use "-"
> 
> w-disable1-gpios
> 

I just went with the spec that defines the signal as W_DISABLE.

> > +    description: GPIO controlled connection to W_DISABLE1# signal. This signal
> > +      is used by the system to disable WiFi radio in the M.2 card. Refer, PCI
> > +      Express M.2 Specification r4.0, sec 3.1.12.3 for more details.
> > +    maxItems: 1
> > +
> > +  w_disable2-gpios:
> > +    description: GPIO controlled connection to W_DISABLE2# signal. This signal
> > +      is used by the system to disable BT radio in the M.2 card. Refer, PCI
> > +      Express M.2 Specification r4.0, sec 3.1.12.3 for more details.
> > +    maxItems: 1
> > +
> > +  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.
> > +    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
> > +
> > +  uim_power_src-gpios:
> 
> property use -
> 

Again, this is as per the spec. If DT maintainers object to it, I'll change it.

- Mani

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