netdev - Re: [PATCH net-next] net: phy: print error message in phy

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Message-ID: <5f65b8e8-8f12-3dfb-77cc-6b87ad834067@gmail.com>
Date:   Sun, 16 Dec 2018 18:16:57 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        David Miller <davem@...emloft.net>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] net: phy: print error message in phy_error

On 16.12.2018 18:02, Florian Fainelli wrote:
> Le 12/16/18 à 7:52 AM, Heiner Kallweit a écrit :
>> So far phy_error() silently stops the PHY state machine. If the network
>> driver doesn't inform about a  MDIO error then the user may wonder why
>> his network is down. So let's inform the user.
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> 
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> 
> Kind of similar to the netdev watchdog on a TX timeout, I wonder if we
> should not just put a WARN() here to get a complete stack trace to help
> debug those events?
> 
AFAICS phy_error() is always (?) caused by a MDIO access error.
Does it help us to know in which code path the MDIO error occurred?

And maybe the stack trace in case of a tx timeout isn't the best
example, at least from my personal experience. I dealt with such cases
and the stack trace never helped. The root cause always was in a totally
different place (wrong chip tx configuration etc.)
But maybe there are other cases where it's useful.

>> ---
>>  drivers/net/phy/phy.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
>> index 890ae1d73..a898fa411 100644
>> --- a/drivers/net/phy/phy.c
>> +++ b/drivers/net/phy/phy.c
>> @@ -739,6 +739,8 @@ static void phy_error(struct phy_device *phydev)
>>  	phydev->state = PHY_HALTED;
>>  	mutex_unlock(&phydev->lock);
>>  
>> +	phydev_err(phydev, "stopping PHY state machine due to error\n");
>> +
>>  	phy_trigger_machine(phydev);
>>  }
>>  
>>
> 
>