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

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Message-ID: <15796ade-68dd-4350-e481-3a3a1e7ce3d5@pensando.io>
Date:   Fri, 19 Jul 2019 11:41:28 -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 7/18/19 7:40 PM, Andrew Lunn wrote:
> On Thu, Jul 18, 2019 at 05:12:07PM -0700, Shannon Nelson wrote:
>> 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.
> Hi Shannon
>
> Looking at the code, i don't see how it can handle this
> correctly. Please look at my comments, particularly the meaning of
> pause->autoneg and describe how the firmware does the right thing,
> given what information it is passed.
>

I guess I'm not sure how much better I can answer your question. Like 
several other devices, we don't support selecting pause->autoneg.  The 
firmware manages the PHY itself, the driver doesn't have direct access 
to the PHY.  The driver passes the tx and rx pause info down to the 
firmware in a command request.  The NIC firmware does an autoneg if 
autoneg is enabled on the port.

sln