linux-kernel - Re: [PATCH net] net: phy: Warn about incorrect mdio_bus_phy

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Message-ID: <20220922053113.250dc095@kernel.org>
Date:   Thu, 22 Sep 2022 05:31:13 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     netdev@...r.kernel.org, opendmb@...il.com,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH net] net: phy: Warn about incorrect
 mdio_bus_phy_resume() state

On Mon,  1 Aug 2022 16:34:03 -0700 Florian Fainelli wrote:
> Calling mdio_bus_phy_resume() with neither the PHY state machine set to
> PHY_HALTED nor phydev->mac_managed_pm set to true is a good indication
> that we can produce a race condition looking like this:
> 
> CPU0						CPU1
> bcmgenet_resume
>  -> phy_resume
>    -> phy_init_hw
>  -> phy_start
>    -> phy_resume  
>                                                 phy_start_aneg()
> mdio_bus_phy_resume
>  -> phy_resume
>     -> phy_write(..., BMCR_RESET)
>      -> usleep()                                  -> phy_read()  
> 
> with the phy_resume() function triggering a PHY behavior that might have
> to be worked around with (see bf8bfc4336f7 ("net: phy: broadcom: Fix
> brcm_fet_config_init()") for instance) that ultimately leads to an error
> reading from the PHY.

Hi Florian! There were some follow ups on this one, were all the known
reports covered at this point or there are still platforms to tweak?