netdev - FEC unbind/bind feature

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 25 Mar 2021 08:04:58 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: FEC unbind/bind feature

Hi Andrew, Florian, Heiner

You are all Ethernet MDIO bus and PHY experts, I have some questions may need your help, thanks a lot in advance.

For many board designs, if it has dual MAC instances, they always share one MDIO bus to save PINs. Such as, i.MX6UL EVK board:

&fec1 {
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_enet1>;
	phy-mode = "rmii";
	phy-handle = <&ethphy0>;
	phy-supply = <&reg_peri_3v3>;
	status = "okay";
};

&fec2 {
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_enet2>;
	phy-mode = "rmii";
	phy-handle = <&ethphy1>;
	phy-supply = <&reg_peri_3v3>;
	status = "okay";

	mdio {
		#address-cells = <1>;
		#size-cells = <0>;

		ethphy0: ethernet-phy@2 {
			compatible = "ethernet-phy-id0022.1560";
			reg = <2>;
			micrel,led-mode = <1>;
			clocks = <&clks IMX6UL_CLK_ENET_REF>;
			clock-names = "rmii-ref";

		};

		ethphy1: ethernet-phy@1 {
			compatible = "ethernet-phy-id0022.1560";
			reg = <1>;
			micrel,led-mode = <1>;
			clocks = <&clks IMX6UL_CLK_ENET2_REF>;
			clock-names = "rmii-ref";
		};
	};
};

For FEC driver now, there is a patch from Fabio to prevent unbind/bind feature since dual FEC controllers share one MDIO bus. (https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/net/ethernet/freescale/fec_main.c?h=next-20210324&id=272bb0e9e8cdc76e04baeefa0cd43019daa0841b)
If we unbind fec2 and then fec1 can't work since MDIO bus is controlled by FEC1, FEC2 can't use it independently.

My question is that if we want to implement unbind/bind feature, what need we do? It seems to abstract an independent MDIO bus for dual FEC instances. I look at the MDIO dt bindings, it seems support such case as it has "reg" property. (Documentation/devicetree/bindings/net/mdio.yaml)

Is there any implements existing in the Linux kernel for a reference? From your opinions, do you think it is necessary to improve it?

Best Regards,
Joakim Zhang