[PATCH net] net: phylink: actually fix ksettings_set() ethtool call

["Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>]

Raju Lakkaraju reported that the below commit caused a regression
with Lan743x drivers and a 2.5G SFP. Sadly, this is because the commit
was utterly wrong. Let's fix this properly by not moving the
linkmode_and(), but instead copying the link ksettings and then
modifying the advertising mask before passing the modified link
ksettings to phylib.

Fixes: df0acdc59b09 ("net: phylink: fix ksettings_set() ethtool call")
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 drivers/net/phy/phylink.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index e237949deee6..cf4e51e48cdd 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -2225,11 +2225,13 @@ int phylink_ethtool_ksettings_set(struct phylink *pl,
 
 	ASSERT_RTNL();
 
-	/* Mask out unsupported advertisements */
-	linkmode_and(config.advertising, kset->link_modes.advertising,
-		     pl->supported);
-
 	if (pl->phydev) {
+		struct ethtool_link_ksettings phy_kset = *kset;
+
+		linkmode_and(phy_kset.link_modes.advertising,
+			     phy_kset.link_modes.advertising,
+			     pl->supported);
+
 		/* We can rely on phylib for this update; we also do not need
 		 * to update the pl->link_config settings:
 		 * - the configuration returned via ksettings_get() will come
@@ -2252,6 +2254,9 @@ int phylink_ethtool_ksettings_set(struct phylink *pl,
 	}
 
 	config = pl->link_config;
+	/* Mask out unsupported advertisements */
+	linkmode_and(config.advertising, kset->link_modes.advertising,
+		     pl->supported);
 
 	/* FIXME: should we reject autoneg if phy/mac does not support it? */
 	switch (kset->base.autoneg) {
-- 
2.30.2