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

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Date:   Fri, 21 Oct 2022 20:27:52 +0900
From:   Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To:     Heiner Kallweit <hkallweit1@...il.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 2022/10/21 20:12, Heiner Kallweit wrote:
> 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 for the clue!
I'll try the flag and check the behavior of MAC/PHY.

Thank you,

---
Best Regards
Kunihiko Hayashi