Re: [PATCH 4/7] dt-bindings: imx6q-pcie: add a property configure refclk pad usage mode

[Rob Herring <robh@kernel.org>]

On Mon, May 10, 2021 at 04:15:06PM +0200, Lucas Stach wrote:
> Starting with the i.MX7, arch PCIe instance has a differential refclk pad,
> which can beused in multiple ways:
> 
> - It's not used at all and the PHY reference clock is provided by a SoC
>   internal source, like on the previous SOCs.
> - It's used as a clock input, for the board to provide a reference clock
>   for the PHY.
> - It's used as a clock output, where the PHY reference clock is provided
>   by a SoC internal source and the same clock is also routed to the
>   refclk pad for consumption of board-level components.
> 
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> ---
>  Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> index 308540df99ef..3ebd8553a818 100644
> --- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> +++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> @@ -38,6 +38,11 @@ Optional properties:
>    The regulator will be enabled when initializing the PCIe host and
>    disabled either as part of the init process or when shutting down the
>    host.
> +- fsl,refclk-pad-mode: Usage mode of the refclk pad. Valid values:
> +  - 0: pad not used. PHY refclock is derived from SoC internal source.
> +  - 1: pad input. PHY refclock is provided externally via the refclk pad.
> +  - 2: pad output. PHY refclock is derived from SoC internal source and
> +       provided on the refclk pad.

Seems like this belongs in the PHY's node?

Or you could determine this based on the PHY's clock source. At least 
for the first 2 cases. Is there a known user for the 3rd case? If so, 
it's possible that what it's connected to needs a clock provider as 
well.

Rob