Re: [PATCH 1/3] arm64: dts: rockchip: Enable USB 2.0 host1 on Radxa ROCK 3B

On Fri, Sep 25, 2026 at 5:56 PM Adam Wermuth [off-list ref] wrote:

Hi,

On Thu, 25 Sep 2026 3:26 PM, Sebastian Reichel wrote:

quoted

Why would this be better suited as an Overlay? Nothing describes the
specific card plugged in as it is auto-discovered via USB. The
overlays are mostly required for things that cannot easily be
auto-detected. FWIW we don't have M.2 Key M as a DT overlay either.

The overlay was Jonas' suggestion, so I'll let him explain his
reasoning. My own understanding was that it would avoid powering the
slot (always-on supply plus RESET#/W_DISABLE1# hogs) on boards where
nothing is plugged in.

That said, I agree that the module itself is auto-discovered via USB,
and the Key M slot on this board is described in the base DT as well,
so I'm fine with keeping the B-key slot there, as in v1.

quoted

Something to consider is, that for Key E and Key M there is a proper
DT binding now: Documentation/devicetree/bindings/connector/pcie-m2-*.yaml

We probably want the same for Key B.

Thanks for the pointer. As far as I can see, a Key B binding would
also need driver support to handle the supply, RESET# and W_DISABLE1#,
so it is a larger piece of work. Would it be acceptable to describe
the slot in the base DT for now and move to a connector binding once
one exists for Key B?

Key B binding would be somewhat more involved than key E or key M. The
spec defines 16 distinct interface mux configurations selected by the
four CONFIG_X pins, which neither key M nor key E have (PCIe vs. SATA,
USB3 vs. SSIC, different audio configs, different I2C configs, etc.).
So it's a bit more than the supply, RESET# and W_DISABLE1#.

See for example [1] where just the PCIe vs. SATA selection is defined.
A proper binding will be needed sooner or later, though.

[1] https://github.com/flipperdevices/u-boot/blob/rk3576/board/flipper/flipper-one/flipper-one-rk3576.c#L41-L172

Best regards,
Alexey