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

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Message-ID: <20190719190715.GO25635@lunn.ch>
Date:   Fri, 19 Jul 2019 21:07:15 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Shannon Nelson <snelson@...sando.io>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH v3 net-next 13/19] ionic: Add initial ethtool support

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
	Andrew