Re: [PATCH v4 5/9] dt-bindings: connector: Add PCIe M.2 Mechanical Key E connector

[Rob Herring]

On Fri, Jan 16, 2026 at 8:43 AM Manivannan Sadhasivam <mani@xxxxxxxxxx> wrote:
>
> On Fri, Jan 16, 2026 at 08:19:07AM -0600, Rob Herring wrote:
> > On Thu, Jan 15, 2026 at 4:42 AM Manivannan Sadhasivam <mani@xxxxxxxxxx> wrote:
> > >
> > > On Wed, Jan 14, 2026 at 11:45:42AM -0600, Rob Herring wrote:
> > > > On Wed, Jan 14, 2026 at 10:14 AM Manivannan Sadhasivam <mani@xxxxxxxxxx> wrote:
> > > > >
> > > > > On Tue, Jan 13, 2026 at 11:14:24AM -0600, Rob Herring wrote:
> > > > > > On Mon, Jan 12, 2026 at 09:56:04PM +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. Spec also provides an optional interface to connect the UIM card,
> > > > > > > but that is not covered in this binding.
> > > > > > >
> > > > > > > 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 000000000000..b65b39ddfd19
> > > > > > > --- /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.
> > > > > >
> > > > > > I don't see any 1.8V supply on the connector. There are 1.8V IOs and you
> > > > > > may need something in DT to ensure those are powered. However, there's
> > > > > > no guarantee that it's a single supply.
> > > > > >
> > > > >
> > > > > 1.8v VIO supply is an optional supply and is only required if the platform
> > > > > supports 1.8v for sideband signals such as PERST#, WAKE#... I can include it in
> > > > > the example for completeness.
> > > >
> > > > My point is that PERST# and WAKE# supplies could be 2 different 1.8V
> > > > supplies and those supply the I/O pads of the GPIO pins (and possibly
> > > > external pull-ups) that drive them. The 1.8V supply doesn't supply
> > > > 1.8V to the slot, so making it a slot/connector property is wrong.
> > > >
> > >
> > > Ok, I get your point that VIO 1.8v supply is just limited to the I/O logic and
> > > not the whole card/adapter. But I don't get your multiple supplies concern. Spec
> > > says, "A 1.8 V supply pin called VIO 1.8 V is used to supply the on-Adapter I/O
> > > buffer circuitry operating at 1.8 V." So it implies that either the single
> > > supply available to the card through VIO might be used to power the whole I/O
> > > circuit logic or the card can derive its own 1.8v supply from 3.3v supply.
> > >
> > > So how come the card can have 2 different 1.8v supplies powering the I/O
> > > circuitry?
> >
> > Is there a pin on the connector for 1.8V supply? I don't have the
> > spec, but the pinout I found[1] didn't show one. If there's a pin,
> > then I have no concern.
> >
>
> Oh yes, there is a single VIO pin defined in the spec for multiple Keys. Since
> it is optional, it could've been omitted in the design you referenced.
>
> So should I name it as vio1v8-supply or vpcie1v8-supply? I don't see any other
> 1.8v supplies other than the VIO supply though.

vpcie1v8 is fine.

Rob