netdev - [PATCH net 3/3] net: dsa: mv88e6xxx: correctly report serdes link failure

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Date:   Wed, 13 Apr 2022 17:54:02 +0100
From:   "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Marek Behún <kabel@...nel.org>,
        netdev@...r.kernel.org
Subject: [PATCH net 3/3] net: dsa: mv88e6xxx: correctly report serdes link
 failure

Phylink wants to know if the link has dropped since the last time state
was retrieved, and the BMSR gives us that. Read the BMSR and use it when
deciding the link state. Fill in the an_complete member as well for the
emulated PHY state.

Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
---
 drivers/net/dsa/mv88e6xxx/serdes.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/dsa/mv88e6xxx/serdes.c b/drivers/net/dsa/mv88e6xxx/serdes.c
index 47bf87d530b0..d94150d8f3f4 100644
--- a/drivers/net/dsa/mv88e6xxx/serdes.c
+++ b/drivers/net/dsa/mv88e6xxx/serdes.c
@@ -53,6 +53,14 @@ static int mv88e6xxx_serdes_pcs_get_state(struct mv88e6xxx_chip *chip,
 					  u16 bmsr, u16 lpa, u16 status,
 					  struct phylink_link_state *state)
 {
+	state->link = false;
+
+	/* If the BMSR reports that the link had failed, report this to
+	 * phylink.
+	 */
+	if (!(bmsr & BMSR_LSTATUS))
+		return 0;
+
 	state->link = !!(status & MV88E6390_SGMII_PHY_STATUS_LINK);
 	state->an_complete = !!(bmsr & BMSR_ANEGCOMPLETE);
 
-- 
2.30.2