linux-kernel - Re: [PATCH v2] lan743x: correctly handle chips with internal PHY

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Message-ID: <20201108041447.GZ933237@lunn.ch>
Date:   Sun, 8 Nov 2020 05:14:47 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Sven Van Asbroeck <thesven73@...il.com>
Cc:     Bryan Whitehead <bryan.whitehead@...rochip.com>,
        David S Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Roelof Berg <rberg@...g-solutions.de>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] lan743x: correctly handle chips with internal PHY

On Fri, Nov 06, 2020 at 08:43:24AM -0500, Sven Van Asbroeck wrote:
> From: Sven Van Asbroeck <thesven73@...il.com>
> 
> Commit 6f197fb63850 ("lan743x: Added fixed link and RGMII support")
> assumes that chips with an internal PHY will never have a devicetree
> entry. This is incorrect: even for these chips, a devicetree entry
> can be useful e.g. to pass the mac address from bootloader to chip:
> 
>     &pcie {
>             status = "okay";
> 
>             host@0 {
>                     reg = <0 0 0 0 0>;
> 
>                     #address-cells = <3>;
>                     #size-cells = <2>;
> 
>                     lan7430: ethernet@0 {
>                             /* LAN7430 with internal PHY */
>                             compatible = "microchip,lan743x";
>                             status = "okay";
>                             reg = <0 0 0 0 0>;
>                             /* filled in by bootloader */
>                             local-mac-address = [00 00 00 00 00 00];
>                     };
>             };
>     };
> 
> If a devicetree entry is present, the driver will not attach the chip
> to its internal phy, and the chip will be non-operational.
> 
> Fix by tweaking the phy connection algorithm:
> - first try to connect to a phy specified in the devicetree
>   (could be 'real' phy, or just a 'fixed-link')
> - if that doesn't succeed, try to connect to an internal phy, even
>   if the chip has a devnode
> 
> Tested on a LAN7430 with internal PHY. I cannot test a device using
> fixed-link, as I do not have access to one.
> 
> Fixes: 6f197fb63850 ("lan743x: Added fixed link and RGMII support")
> Tested-by: Sven Van Asbroeck <thesven73@...il.com> # lan7430
> Signed-off-by: Sven Van Asbroeck <thesven73@...il.com>
> ---
> 
> v1 -> v2:
>     Andrew Lunn: keep patch minimal and correct, so keep open-coded version
>     of of_phy_get_and_connect().

Hi Sven

Why is it required to remove adapter->phy_mode? It is not clear to me
what this change has to do with not looking for an internal PHY.

> @@ -1063,6 +1065,7 @@ static int lan743x_phy_open(struct lan743x_adapter *adapter)
>  
>  	phy_start(phydev);
>  	phy_start_aneg(phydev);
> +	phy_attached_info(phydev);

This also has nothing to do with the problem you are fixing. It is a
sensible thing to do, but it should be a separate patch, and target
net-next, since it is not a fix.

	  Andrew