netdev - Re: [PATCH net] net: phy: Avoid WARN_ON for PHY

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Date:   Fri, 21 Oct 2022 13:12:34 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Andrew Lunn <andrew@...n.ch>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: phy: Avoid WARN_ON for PHY_NOLINK during
 resuming

On 21.10.2022 11:35, Kunihiko Hayashi wrote:
> Hi Heiner,
> 
> Thank you for your comment.
> 
> On 2022/10/21 17:38, Heiner Kallweit wrote:
>> On 21.10.2022 09:41, Kunihiko Hayashi wrote:
>>> When resuming from sleep, if there is a time lag from link-down to link-up
>>> due to auto-negotiation, the phy status has been still PHY_NOLINK, so
>>> WARN_ON dump occurs in mdio_bus_phy_resume(). For example, UniPhier AVE
>>> ethernet takes about a few seconds to link up after resuming.
>>>
>> That autoneg takes some time is normal. If this would actually the root
>> cause then basically every driver should be affected. But it's not.
> 
> Although the auto-neg should happen normally, I'm not sure about other
> platforms.
> 
>>> To avoid this issue, should remove PHY_NOLINK the WARN_ON conditions.
>>>
>>> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
>>> ---
>>>   drivers/net/phy/phy_device.c | 8 ++++----
>>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
>>> index 57849ac0384e..c647d027bb5d 100644
>>> --- a/drivers/net/phy/phy_device.c
>>> +++ b/drivers/net/phy/phy_device.c
>>> @@ -318,12 +318,12 @@ static __maybe_unused int mdio_bus_phy_resume(struct
>>> device *dev)
>>>       phydev->suspended_by_mdio_bus = 0;
>>>
>>>       /* If we managed to get here with the PHY state machine in a state
>>> -     * neither PHY_HALTED, PHY_READY nor PHY_UP, this is an indication
>>> -     * that something went wrong and we should most likely be using
>>> -     * MAC managed PM, but we are not.
>>> +     * neither PHY_HALTED, PHY_READY, PHY_UP nor PHY_NOLINK, this is an
>>> +     * indication that something went wrong and we should most likely
>>> +     * be using MAC managed PM, but we are not.
>>>        */
>>
>> Did you read the comment you're changing? ave_resume() calls phy_resume(),
>> so you should follow the advice in the comment.
> 
> I understand something is wrong with "PHY_NOLINK" here, and need to investigate
> the root cause of the phy state issue.
> 
Best look at how phydev->mac_managed_pm is used in phylib and by MAC drivers.

> Thank you,
> 
> ---
> Best Regards
> Kunihiko Hayashi