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

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Message-ID: <26ef199c-cf45-57b5-70cc-9ee42879d96e@gmail.com>
Date:   Thu, 22 Sep 2022 08:29:34 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
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>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net: phy: Warn about incorrect mdio_bus_phy_resume()
 state



On 9/22/2022 5:31 AM, Jakub Kicinski wrote:
> 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?

This is the only active thread that I am aware of, and Lukas and I are 
in agreement as to what to do next:

https://lore.kernel.org/all/20220918191333.GA2107@wunner.de/

expect him to submit a follow on the warning condition to deal with the 
smsc95xx USB driver.

Thanks!
-- 
Florian