netdev - [PATCH net-next 1/1] net: dsa: fix fixed-link port registration

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Message-Id: <20190811014650.28141-1-marek.behun@nic.cz>
Date:   Sun, 11 Aug 2019 03:46:50 +0200
From:   Marek Behún <marek.behun@....cz>
To:     netdev@...r.kernel.org
Cc:     Marek Behún <marek.behun@....cz>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Sebastian Reichel <sebastian.reichel@...labora.co.uk>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: [PATCH net-next 1/1] net: dsa: fix fixed-link port registration

Commit 88d6272acaaa ("net: phy: avoid unneeded MDIO reads in
genphy_read_status") broke fixed link DSA port registration in
dsa_port_fixed_link_register_of: the genphy_read_status does not do what
it is supposed to and the following adjust_link is given wrong
parameters.

This causes a regression on Turris Omnia, where the mvneta driver for
the interface connected to the switch reports crc errors, for some
reason.

I realize this fix is not ideal, something else could change in genphy
functions which could cause DSA fixed-link port to break again.
Hopefully DSA fixed-link port functionality will be converted to phylink
API soon.

Signed-off-by: Marek Behún <marek.behun@....cz>
Cc: Heiner Kallweit <hkallweit1@...il.com>
Cc: Sebastian Reichel <sebastian.reichel@...labora.co.uk>
Cc: Vivien Didelot <vivien.didelot@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>
Cc: Florian Fainelli <f.fainelli@...il.com>
Cc: David S. Miller <davem@...emloft.net>
---
 net/dsa/port.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/net/dsa/port.c b/net/dsa/port.c
index 363eab6df51b..c424ebb373e1 100644
--- a/net/dsa/port.c
+++ b/net/dsa/port.c
@@ -485,6 +485,17 @@ static int dsa_port_fixed_link_register_of(struct dsa_port *dp)
 	phydev->interface = mode;
 
 	genphy_config_init(phydev);
+
+	/*
+	 * Commit 88d6272acaaa caused genphy_read_status not to do it's work if
+	 * autonegotiation is enabled and link status did not change. This is
+	 * the case for fixed_phy. By setting phydev->link = 0 before the call
+	 * to genphy_read_status we force it to read and fill in the parameters.
+	 *
+	 * Hopefully this dirty hack will be removed soon by converting DSA
+	 * fixed link ports to phylink API.
+	 */
+	phydev->link = 0;
 	genphy_read_status(phydev);
 
 	if (ds->ops->adjust_link)
-- 
2.21.0