netdev - Re: [PATCH 3/6] ravb: remove custom .set_link

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Message-ID: <6f908ff0-254b-4378-27d3-5ff973328d88@mentor.com>
Date:   Mon, 28 May 2018 12:51:03 +0300
From:   Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        "David S. Miller" <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>, <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH 3/6] ravb: remove custom .set_link_ksettings from ethtool
 ops

Hello Sergei,

On 05/26/2018 10:50 PM, Sergei Shtylyov wrote:
> On 05/24/2018 02:11 PM, Vladimir Zapolskiy wrote:
> 
>> The change replaces a custom implementation of .set_link_ksettings
>> callback with a shared phy_ethtool_set_link_ksettings(), this fixes
>> sleep in atomic context bug, which is encountered every time when link
>> settings are changed by ethtool.
> 
>    Seeing it now...
> 
>> Now duplex mode setting is enforced in ravb_adjust_link() only, also
>> now TX/RX is disabled when link is put down or modifications to E-MAC
>> registers ECMR and GECMR are expected for both cases of checked and
>> ignored link status pin state from E-MAC interrupt handler.
>>
>> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
>> ---
>>  drivers/net/ethernet/renesas/ravb_main.c | 58 +++++++++-----------------------
>>  1 file changed, 15 insertions(+), 43 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>> index 3d91caa44176..0d811c02ff34 100644
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>> @@ -980,6 +980,13 @@ static void ravb_adjust_link(struct net_device *ndev)
>>  	struct ravb_private *priv = netdev_priv(ndev);
>>  	struct phy_device *phydev = ndev->phydev;
>>  	bool new_state = false;
>> +	unsigned long flags;
>> +
>> +	spin_lock_irqsave(&priv->lock, flags);
>> +
>> +	/* Disable TX and RX right over here, if E-MAC change is ignored */
>> +	if (priv->no_avb_link)
>> +		ravb_rcv_snd_disable(ndev);
>>  
>>  	if (phydev->link) {
>>  		if (phydev->duplex != priv->duplex) {
>> @@ -997,18 +1004,21 @@ static void ravb_adjust_link(struct net_device *ndev)
>>  			ravb_modify(ndev, ECMR, ECMR_TXF, 0);
>>  			new_state = true;
>>  			priv->link = phydev->link;
>> -			if (priv->no_avb_link)
>> -				ravb_rcv_snd_enable(ndev);
>>  		}
>>  	} else if (priv->link) {
>>  		new_state = true;
>>  		priv->link = 0;
>>  		priv->speed = 0;
>>  		priv->duplex = -1;
>> -		if (priv->no_avb_link)
>> -			ravb_rcv_snd_disable(ndev);
>>  	}
>>  
>> +	/* Enable TX and RX right over here, if E-MAC change is ignored */
>> +	if (priv->no_avb_link && phydev->link)
>> +		ravb_rcv_snd_enable(ndev);
>> +
>> +	mmiowb();
>> +	spin_unlock_irqrestore(&priv->lock, flags);
>> +
> 
>    I like this part. :-)
> 

A weight off my mind :) And I hope that this change will remain the less
questionable one, other ones from the series are trivial.

Anyway I hope it is understandable that this part of the change can not
be simply extracted from the rest one below, otherwise there'll be bugs of
another type intorduced.

>>  	if (new_state && netif_msg_link(priv))
>>  		phy_print_status(phydev);
>>  }
>> @@ -1096,44 +1106,6 @@ static int ravb_phy_start(struct net_device *ndev)
>>  	return 0;
>>  }
>>  
>> -static int ravb_set_link_ksettings(struct net_device *ndev,
>> -				   const struct ethtool_link_ksettings *cmd)
>> -{
>> -	struct ravb_private *priv = netdev_priv(ndev);
>> -	unsigned long flags;
>> -	int error;
>> -
>> -	if (!ndev->phydev)
>> -		return -ENODEV;
>> -
>> -	spin_lock_irqsave(&priv->lock, flags);
>> -
>> -	/* Disable TX and RX */
>> -	ravb_rcv_snd_disable(ndev);
>> -
>> -	error = phy_ethtool_ksettings_set(ndev->phydev, cmd);
>> -	if (error)
>> -		goto error_exit;
>> -
>> -	if (cmd->base.duplex == DUPLEX_FULL)
>> -		priv->duplex = 1;
>> -	else
>> -		priv->duplex = 0;
>> -
>> -	ravb_set_duplex(ndev);
>> -
>> -error_exit:
>> -	mdelay(1);
>> -
>> -	/* Enable TX and RX */
>> -	ravb_rcv_snd_enable(ndev);
>> -
>> -	mmiowb();
>> -	spin_unlock_irqrestore(&priv->lock, flags);
>> -
>> -	return error;
>> -}
>> -
> 
>    But this part is clearly lumping it all together... 

Please elaborate.

> 
> [...]
>> @@ -1357,7 +1329,7 @@ static const struct ethtool_ops ravb_ethtool_ops = {
>>  	.set_ringparam		= ravb_set_ringparam,
>>  	.get_ts_info		= ravb_get_ts_info,
>>  	.get_link_ksettings	= phy_ethtool_get_link_ksettings,
>> -	.set_link_ksettings	= ravb_set_link_ksettings,
>> +	.set_link_ksettings	= phy_ethtool_set_link_ksettings,
> 
>    Should have been a part of the final patch in the fix/enhancement chain...

Please elaborate.

Do you mean that firstly I have to make erroneous ravb_set_link_ksettings()
to look similar to phy_ethtool_set_link_ksettings() and then remove it?

As I see it in the current context (removal of ravb_set_duplex() call and
so on), the problem with this approach is that the actual fix change will
be done on top of a number of enchancement changes, thus it contradicts to
the accepted development/maintenace model "fixes first", and most probably
it won't be possible to backport the real fix, however this sole change can
be backported.

> 
>>  	.get_wol		= ravb_get_wol,
>>  	.set_wol		= ravb_set_wol,
>>  };
> 

--
With best wishes,
Vladimir