netdev - [PATCH] net: phylink: Update SFP selected interface on advertising changes

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Date:   Thu, 26 Aug 2021 07:12:30 +0000
From:   Nathan Rossi <nathan@...hanrossi.com>
To:     netdev@...r.kernel.org
Cc:     Nathan Rossi <nathan@...hanrossi.com>,
        Nathan Rossi <nathan.rossi@...i.com>,
        Russell King <linux@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH] net: phylink: Update SFP selected interface on advertising changes

From: Nathan Rossi <nathan.rossi@...i.com>

Currently changes to the advertising state via ethtool do not cause any
reselection of the configured interface mode after the SFP is already
inserted and initially configured.

While it is not typical to change the advertised link modes for an
interface using an SFP in certain use cases it is desirable. In the case
of a SFP port that is capable of handling both SFP and SFP+ modules it
will automatically select between 1G and 10G modes depending on the
supported mode of the SFP. However if the SFP module is capable of
working in multiple modes (e.g. a SFP+ DAC that can operate at 1G or
10G), one end of the cable may be attached to a SFP 1000base-x port thus
the SFP+ end must be manually configured to the 1000base-x mode in order
for the link to be established.

This change causes the ethtool setting of advertised mode changes to
reselect the interface mode so that the link can be established.

Signed-off-by: Nathan Rossi <nathan.rossi@...i.com>
---
 drivers/net/phy/phylink.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 2cdf9f989d..8986c7a0c5 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -1525,6 +1525,22 @@ int phylink_ethtool_ksettings_set(struct phylink *pl,
 	if (config.an_enabled && phylink_is_empty_linkmode(config.advertising))
 		return -EINVAL;

+	/* If this link is with an SFP, ensure that changes to advertised modes
+	 * also cause the associated interface to be selected such that the
+	 * link can be configured correctly.
+	 */
+	if (pl->sfp_port && pl->sfp_bus) {
+		config.interface = sfp_select_interface(pl->sfp_bus,
+							config.advertising);
+		if (config.interface == PHY_INTERFACE_MODE_NA) {
+			phylink_err(pl,
+				    "selection of interface failed, advertisement %*pb\n",
+				    __ETHTOOL_LINK_MODE_MASK_NBITS,
+				    config.advertising);
+			return -EINVAL;
+		}
+	}
+
 	mutex_lock(&pl->state_mutex);
 	pl->link_config.speed = config.speed;
 	pl->link_config.duplex = config.duplex;
---
2.33.0