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

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Message-ID: <087d62dc-5a73-b924-8b03-d92fc03acd23@pensando.io>
Date:   Fri, 19 Jul 2019 13:20:25 -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 7/19/19 12:07 PM, Andrew Lunn wrote:
> On Fri, Jul 19, 2019 at 11:41:28AM -0700, Shannon Nelson wrote:
>> 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.
> Hi Shannon
>
> Thanks. That was the information i was looking for.
>
> Please return -EOPNOTSUPP if pause->autoneg indicates autoneg results
> should not be used. Your firmware does not support it, so the driver
> should error out. Also the get function should use a hard coded value
> for pause->autoneg.
>
> If you ever fix your firmware, you can add full support for pause
> configuration.
>
>

Thanks for the help,
sln