netdev - Re: [PATCH 2/2] dt-bindings: net: phy: vsc8531: document 'vsc8531,clkout-freq-mhz' property

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Date: Sat, 8 Jul 2023 20:25:31 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Alexandru Ardelean <alex@...uggie.ro>
Cc: netdev@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
	conor+dt@...nel.org, hkallweit1@...il.com, linux@...linux.org.uk,
	olteanv@...il.com, marius.muresan@....ro
Subject: Re: [PATCH 2/2] dt-bindings: net: phy: vsc8531: document
 'vsc8531,clkout-freq-mhz' property

On Thu, Jul 06, 2023 at 11:15:54AM +0300, Alexandru Ardelean wrote:
> For VSC8351 and similar PHYs, a new property was added to generate a clock
> signal on the CLKOUT pin.
> This change documents the change in the device-tree bindings doc.
> 
> Signed-off-by: Alexandru Ardelean <alex@...uggie.ro>
> ---
>  Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> index 0a3647fe331b..133bdd644618 100644
> --- a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> +++ b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> @@ -31,6 +31,10 @@ Optional properties:
>  			  VSC8531_LINK_100_ACTIVITY (2),
>  			  VSC8531_LINK_ACTIVITY (0) and
>  			  VSC8531_DUPLEX_COLLISION (8).
> +- vsc8531,clkout-freq-mhz : For VSC8531 and similar PHYs, this will output
> +			  a clock signal on the CLKOUT pin of the chip.
> +			  The supported values are 25, 50 & 125 Mhz.
> +			  Default value is no clock signal on the CLKOUT pin.

It is possible this could cause regressions. The bootloader could
turned the clock on, and then Linux leaves it alone. Now, it will get
turned off unless a DT property is added.

I prefer to explicitly have the property, so there is no dependency on
the bootloader, so lets leave it like this. But if we do get
regressions reported, this might need to change.

   Andrew