netdev - [PATCH v2 net-next 1/3] net: dsa: sja1105: Don't check state->link in phylink_mac

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Date:   Fri, 28 Jun 2019 00:46:35 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     linux@...linux.org.uk, f.fainelli@...il.com,
        vivien.didelot@...il.com, andrew@...n.ch, davem@...emloft.net
Cc:     netdev@...r.kernel.org, Vladimir Oltean <olteanv@...il.com>,
        Russell King <rmk+kernel@...linux.org.uk>
Subject: [PATCH v2 net-next 1/3] net: dsa: sja1105: Don't check state->link in phylink_mac_config

It has been pointed out that PHYLINK can call mac_config only to update
the phy_interface_type and without knowing what the AN results are.

Experimentally, when this was observed to happen, state->link was also
unset, and therefore was used as a proxy to ignore this call. However it
is also suggested that state->link is undefined for this callback and
should not be relied upon.

So let the previously-dead codepath for SPEED_UNKNOWN be called, and
update the comment to make sure the MAC's behavior is sane.

Cc: Russell King <rmk+kernel@...linux.org.uk>
Signed-off-by: Vladimir Oltean <olteanv@...il.com>
---
 drivers/net/dsa/sja1105/sja1105_main.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
index caebf76eaa3e..da1736093b06 100644
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -715,7 +715,13 @@ static int sja1105_adjust_port_config(struct sja1105_private *priv, int port,
 
 	switch (speed_mbps) {
 	case SPEED_UNKNOWN:
-		/* No speed update requested */
+		/* PHYLINK called sja1105_mac_config() to inform us about
+		 * the state->interface, but AN has not completed and the
+		 * speed is not yet valid. UM10944.pdf says that setting
+		 * SJA1105_SPEED_AUTO at runtime disables the port, so that is
+		 * ok for power consumption in case AN will never complete -
+		 * otherwise PHYLINK should come back with a new update.
+		 */
 		speed = SJA1105_SPEED_AUTO;
 		break;
 	case SPEED_10:
@@ -766,9 +772,6 @@ static void sja1105_mac_config(struct dsa_switch *ds, int port,
 {
 	struct sja1105_private *priv = ds->priv;
 
-	if (!state->link)
-		return;
-
 	sja1105_adjust_port_config(priv, port, state->speed);
 }
 
-- 
2.17.1