netdev - Re: [PATCH] net: fec: Fix phy_device lookup for phy_reset_after_clk

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Date:   Sat, 10 Oct 2020 10:45:08 +0200
From:   Marek Vasut <marex@...x.de>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org,
        Christoph Niedermaier <cniedermaier@...electronics.com>,
        "David S . Miller" <davem@...emloft.net>,
        NXP Linux Team <linux-imx@....com>,
        Richard Leitner <richard.leitner@...data.com>,
        Shawn Guo <shawnguo@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH] net: fec: Fix phy_device lookup for
 phy_reset_after_clk_enable()

On 10/9/20 8:02 PM, Jakub Kicinski wrote:
> On Fri, 9 Oct 2020 19:34:10 +0200 Marek Vasut wrote:
>>>>> To an untrained eye this looks pretty weird.    
>>>>
>>>> I see, I'm not quite sure how to address this comment.  
>>>
>>> If ndev->phydev sometimes is not-NULL on open, then that's a valid
>>> state to be in. Why not make sure that we're always in that state 
>>> and can depend on ndev->phydev rather than rummaging around for 
>>> the phy_device instance.  
>>
>> Nope, the problem is in probe() in this case.
> 
> In that case it would be cleaner to pass fep and phydev as arguments
> into fec_enet_clk_enable(), rather than netdev, and have only probe()
> do the necessary dance.

So correction, the problem does only happen in open(), in probe() the
phydev->drv is still NULL so the PHY reset cannot be triggered. In
open(), first the clock have to be enabled, then the reset must toggle,
then the PHY IDs can be reliably read.

I suspect reset in probe() will need another patch.