netdev - Re: MT7621 SoC Traffic Won't Flow on RGMII2 Bus/2nd GMAC

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Date:   Mon, 24 Jan 2022 09:34:23 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Arınç ÜNAL <arinc.unal@...nc9.com>,
        DENG Qingfang <dqfext@...il.com>,
        Luiz Angelo Daros de Luca <luizluca@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        John Crispin <john@...ozen.org>,
        Siddhant Gupta <siddhantgupta416@...il.com>,
        Ilya Lipnitskiy <ilya.lipnitskiy@...il.com>,
        Sergio Paracuellos <sergio.paracuellos@...il.com>,
        Felix Fietkau <nbd@....name>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>,
        René van Dorst <opensource@...rst.com>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        netdev <netdev@...r.kernel.org>, linux-mips@...r.kernel.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, openwrt-devel@...ts.openwrt.org,
        erkin.bozoglu@...ont.com
Subject: Re: MT7621 SoC Traffic Won't Flow on RGMII2 Bus/2nd GMAC



On 1/24/2022 9:26 AM, Russell King (Oracle) wrote:
> On Mon, Jan 24, 2022 at 09:13:38AM -0800, Florian Fainelli wrote:
>> On 1/23/2022 7:26 AM, Andrew Lunn wrote:
>>> On Sun, Jan 23, 2022 at 11:33:04AM +0300, Arınç ÜNAL wrote:
>>>> Hey Deng,
>>>>
>>>> On 23/01/2022 09:51, DENG Qingfang wrote:
>>>>> Hi,
>>>>>
>>>>> Do you set the ethernet pinmux correctly?
>>>>>
>>>>> &ethernet {
>>>>>        pinctrl-names = "default";
>>>>>        pinctrl-0 = <&rgmii1_pins &rgmii2_pins &mdio_pins>;
>>>>> };
>>>>
>>>> This fixed it! We did have &rgmii2_pins on the gmac1 node (it was originally
>>>> on external_phy) so we never thought to investigate the pinctrl
>>>> configuration further! Turns out &rgmii2_pins needs to be defined on the
>>>> ethernet node instead.
>>>
>>> PHYs are generally external, so pinmux on them makes no sense. PHYs in
>>> DT are not devices in the usual sense, so i don't think the driver
>>> core will handle pinmux for them, even if you did list them.
>>
>> Not sure I understand your comment here, this is configuring the pinmux on
>> the SoC side in order for the second RGMII interface's data path to work.
> 
> The pinmux configuration was listed under the external PHY node, which
> is qutie unusual. In the case of phylib and external ethernet PHYs,
> this can be a problem.
> 
> The pinmux configuration is normally handled at device probe time by
> the device model, but remember phylib bypasses that when it attaches
> the generic PHY driver - meaning you don't get the pinmux configured.
> 
> What this means is that pinmux configuration in ethernet PHY nodes is
> unreliable. It will only happen if we have a specific driver for the
> PHY and the driver model binds that driver.
> 
> Of course, if we killed the generic driver, that would get around this
> issue by requiring every PHY to have its own specific driver, but there
> would be many complaints because likely lots would stop working.

I suppose that explains why this is still in staging then :) Andrew's 
answer makes more sense now, thanks.
-- 
Florian