linux-kernel - Re: [PATCH v5 2/3] dt-bindings: net: mscc-vsc8531: add optional clock properties

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Message-ID: <a877e41d-4c3c-c4c2-1875-71e1e08cf977@gmail.com>
Date:   Thu, 18 Jun 2020 22:01:58 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Heiko Stuebner <heiko@...ech.de>, davem@...emloft.net,
        kuba@...nel.org
Cc:     robh+dt@...nel.org, andrew@...n.ch, hkallweit1@...il.com,
        linux@...linux.org.uk, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        christoph.muellner@...obroma-systems.com,
        Heiko Stuebner <heiko.stuebner@...obroma-systems.com>
Subject: Re: [PATCH v5 2/3] dt-bindings: net: mscc-vsc8531: add optional clock
 properties



On 6/18/2020 5:11 AM, Heiko Stuebner wrote:
> From: Heiko Stuebner <heiko.stuebner@...obroma-systems.com>
> 
> Some mscc ethernet phys have a configurable clock output, so describe the
> generic properties to access them in devicetrees.
> 
> Signed-off-by: Heiko Stuebner <heiko.stuebner@...obroma-systems.com>
> ---
>  Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> index 5ff37c68c941..67625ba27f53 100644
> --- a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> +++ b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
> @@ -1,6 +1,8 @@
>  * Microsemi - vsc8531 Giga bit ethernet phy
>  
>  Optional properties:
> +- clock-output-names	: Name for the exposed clock output
> +- #clock-cells		: should be 0
>  - vsc8531,vddmac	: The vddmac in mV. Allowed values is listed
>  			  in the first row of Table 1 (below).
>  			  This property is only used in combination
> 

With that approach, you also need to be careful as a driver writer to
ensure that you have at least probed the MDIO bus to ensure that the PHY
device has been created (and therefore it is available as a clock
provider) if that same Ethernet MAC is a consumer of that clock (which
it appears to be). Otherwise you may just never probe and be trapped in
a circular dependency.
-- 
Florian