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Subject: Re: [PATCH net] net: phy: Avoid WARN_ON for PHY_NOLINK during
 resuming
To:     Heiner Kallweit <hkallweit1@gmail.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Russell King <linux@armlinux.org.uk>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20221021074154.25906-1-hayashi.kunihiko@socionext.com>
 <4d2d6349-6910-3e73-e6c5-db9041bcfdb8@gmail.com>
From:   Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Message-ID: <86262217-a620-dc5b-cf5a-3a23ea869834@socionext.com>
Date:   Fri, 21 Oct 2022 18:35:09 +0900
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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@socionext.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.

Thank you,

---
Best Regards
Kunihiko Hayashi