netdev - Re: [PATCH v3 net-next 13/19] ionic: Add initial ethtool support

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Message-ID: <00a22345-4904-57b4-f40b-9ddd2e7398ec@pensando.io>
Date:   Thu, 18 Jul 2019 17:12:07 -0700
From:   Shannon Nelson <snelson@...sando.io>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH v3 net-next 13/19] ionic: Add initial ethtool support

On 7/17/19 8:28 PM, Andrew Lunn wrote:
> On Fri, Jul 12, 2019 at 10:16:31PM -0700, Shannon Nelson wrote:
>> On 7/8/19 7:14 PM, Andrew Lunn wrote:
>>>> +static int ionic_set_pauseparam(struct net_device *netdev,
>>>> +				struct ethtool_pauseparam *pause)
>>>> +{
>>>> +	struct lif *lif = netdev_priv(netdev);
>>>> +	struct ionic *ionic = lif->ionic;
>>>> +	struct ionic_dev *idev = &lif->ionic->idev;
>>>> +
>>>> +	u32 requested_pause;
>>>> +	u32 cur_autoneg;
>>>> +	int err;
>>>> +
>>>> +	cur_autoneg = idev->port_info->config.an_enable ? AUTONEG_ENABLE :
>>>> +								AUTONEG_DISABLE;
>>>> +	if (pause->autoneg != cur_autoneg) {
>>>> +		netdev_info(netdev, "Please use 'ethtool -s ...' to change autoneg\n");
>>>> +		return -EOPNOTSUPP;
>>>> +	}
>>>> +
>>>> +	/* change both at the same time */
>>>> +	requested_pause = PORT_PAUSE_TYPE_LINK;
>>>> +	if (pause->rx_pause)
>>>> +		requested_pause |= IONIC_PAUSE_F_RX;
>>>> +	if (pause->tx_pause)
>>>> +		requested_pause |= IONIC_PAUSE_F_TX;
>>>> +
>>>> +	if (requested_pause == idev->port_info->config.pause_type)
>>>> +		return 0;
>>>> +
>>>> +	idev->port_info->config.pause_type = requested_pause;
>>>> +
>>>> +	mutex_lock(&ionic->dev_cmd_lock);
>>>> +	ionic_dev_cmd_port_pause(idev, requested_pause);
>>>> +	err = ionic_dev_cmd_wait(ionic, devcmd_timeout);
>>>> +	mutex_unlock(&ionic->dev_cmd_lock);
>>>> +	if (err)
>>>> +		return err;
>>> Hi Shannon
>>>
>>> I've no idea what the firmware black box is doing, but this looks
>>> wrong.
>>>
>>> pause->autoneg is about if the results of auto-neg should be used or
>>> not. If false, just configure the MAC with the pause settings and you
>>> are done. If the interface is being forced, so autoneg in general is
>>> disabled, just configure the MAC and you are done.
>>>
>>> If pause->autoneg is true and the interface is using auto-neg as a
>>> whole, you pass the pause values to the PHY for it to advertise and
>>> trigger an auto-neg. Once autoneg has completed, and the resolved
>>> settings are available, the MAC is configured with the resolved
>>> values.
>>>
>>> Looking at this code, i don't see any difference between configuring
>>> the MAC or configuring the PHY. I would expect pause->autoneg to be
>>> part of requested_pause somehow, so the firmware knows what is should
>>> do.
>>>
>>> 	Andrew
>> In this device there's actually very little the driver can do to directly
>> configure the mac or phy besides passing through to the firmware what the
>> user has requested - that happens here for the pause values, and in
>> ionic_set_link_ksettings() for autoneg.  The firmware is managing the port
>> based on these requests with the help of internally configured rules defined
>> in a customer setting.
> I get that. But the firmware needs to conform to what Linux
> expects. And what i see here does not conform. That is why i gave a
> bit of detail in my reply.
>
> What exactly does the firmware do? Once we know that, we can figure
> out when the driver should return -EOPNOTSUPP because of firmware
> limitations, and what it can configure and should return 0.

Because this is fairly smart FW, it handles this as expected.  I can add 
this as another comment in the code.

sln